Fe-based metallic glasses as efficient oxygen scavengers

Domain: chemistry
Published: 2026-04-13
Editorial outcome: minor_revision

Abstract
Ubiquitous oxygen drives degradation, spoilage, and side reactions, making oxygen scavenging essential for materials preservation and reaction stabilization. However, conventional oxygen scavengers exhibit limited oxygen removal rates and capacities far below their theoretical maximums, wasting resources while lagging behind industry needs. Here, we report Fe-based metallic glasses as efficient oxygen scavengers, achieving oxygen removal rates 1–4 orders of magnitude higher than conventional systems. In FeSiB metallic glass, Fe oxidation synergistically activates Si, delivering a 24-hour oxygen removal capacity of 1.439 L g-1—reaching the Fe-based theoretical limit—and a 48-hour capacity of 1.596 L g-1, surpassing it. Density functional theory calculations reveal that the amorphous structure significantly lowers the oxygen adsorption energy barrier and facilitates O–O bond cleavage. Moreover, the generated self-reinforcing microdomains mediate O2/H2O transport via robust autocatalytic cycling. These results highlight a promising strategy for oxygen potential control and suggest a possible paradigm for catalytic applications.

Introduction
Though essential to life, the ubiquity of oxygen drives unwanted reactions, making effective scavenging crucial for food and pharmaceutical preservation, cultural relics conservation, and chemical synthesis1-5. Fe-based scavengers, the most prevalent type, can remove oxygen through a redox reaction that proceeds in electrolyte-containing environments1,6. Theoretically, 1 g of iron can remove oxygen from approximately 1566 mL of air at 298 K; however, the actual performance falls far short7, reflecting decades of stagnant efficiency and significant resource waste. Moreover, the performance of conventional scavengers remains fundamentally limited by three key challenges: intrinsically low oxygen adsorption activity, surface passivation due to oxidation product accumulation, and a sharp decline in reaction kinetics under low-oxygen conditions—a limitation widely deemed unavoidable6-11. These constraints hinder their use in demanding applications like gas purification and catalyst protection.

Metallic glasses (MGs) are known for their exceptional mechanical and functional properties12-16, with Fe-based MGs being particularly promising for large-scale applications due to their good glass-forming ability and low cost17. While they have been widely used as soft-magnetic materials, their potential in chemical reactions remains largely unexplored.

In this study, we report the use of Fe-based MGs as oxygen scavengers, achieving unmatched efficiency that far exceeds conventional materials. Fe78Si9B13 (FeSiB) MG exhibits excellent oxygen scavenging performance even at a low temperature of 278 K, whereas conventional Fe-based oxygen scavengers are nearly ineffective. Kinetic studies reveal a self-accelerating oxygen scavenging process, while density functional theory (DFT) calculations show that FeSiB MG possesses significantly lower oxygen adsorption energy barrier than crystalline iron. Moreover, the formation of a unique coupled structure—comprising moisture-retaining and adsorption zones—endows the system with strong autocatalytic behavior. These features overcome long-standing limitations of conventional systems and enable exceptional performance under low-oxygen conditions. Their marked superiority and low cost over existing benchmarks position them as enabling materials for next-generation oxygen-sensitive applications (Fig. 1a).

Results
Accelerating oxygen removal kinetics
To evaluate oxygen removal performance, we compared FeSiB MG, pure iron, and reduced iron (commonly used in industry) powders in 500 mL sealed air under saline and non-saline conditions. Using 2 g samples with matched volumetric particle sizes (Supplementary Fig. 1), we added either 1 g ultrapure water (non-saline) or 1 wt% NaCl solution (saline), plus 0.8 g diatomite as a moisture-retaining agent. This controlled setup enabled direct performance comparisons under identical conditions.

Fig. 1b,c demonstrates the superior oxygen removal kinetics of FeSiB MG. Even under non-saline conditions, it achieved complete oxygen removal in just 11.9 hours, showing high reactivity (Fig. 1b). The complete oxygen removal time here is defined as the period required for the oxygen concentration <0.05%, corresponding to >99.7% oxygen removal. In contrast, pure iron and reduced iron showed much slower kinetics and activity decay after 4 hours due to surface passivation. Reduced iron outperformed pure iron owing to its porous structure with much larger surface area. Adding 1 wt% NaCl significantly enhanced the oxygen removal performance of all three materials (Fig. 1c), confirming the role of electrolyte in promoting electron transfer. FeSiB MG achieved a shorter removal time of 5.6 hours, while pure and reduced iron powders still failed to reach complete removal within 24 hours, even under optimized conditions.

In this reaction system, given the ample metal supply and continuous oxygen depletion, oxygen removal kinetics can be described using the pseudo-first-order kinetic model18-20, the apparent rate constant k can be obtained by Equation (1):
k = -ln(C/C0)/t (1)
where C represents the real-time oxygen concentration, C0 is the initial oxygen concentration, and t is the reaction time. Using this equation, the data from Fig. 1b,c were replotted in Fig. 1d,e, where the curve slope at each point reflects the instantaneous reaction rate.

As shown in Fig. 1d, the -ln(C/C0) curve for FeSiB MG displays exponential-type growth, indicating a continuously accelerating reaction rate that deviates from traditional kinetics. In contrast, pure iron and reduced iron show curves that level off, reflecting declining activity. Under saline conditions, FeSiB MG still follows an accelerating trend with a steeper slope (Fig. 1e), confirming electrolyte-enhanced kinetics. Meanwhile, the curves for pure iron and reduced iron become nearly linear, aligning with pseudo-first-order behavior.

Differentiating the curves in Fig. 1d,e yields Fig. 1f,g, where the vertical coordinate represents the instantaneous oxygen removal rate. FeSiB MG shows a much higher initial rate than the two crystalline iron powders, confirming its intrinsically high reactivity. All materials exhibit a slight rate dip in the first 1–2 hours, likely due to initial oxide formation hindering internal oxidation. Uniquely, FeSiB MG displays accelerating kinetics—starting after 3 hours without electrolyte, and as early as 1 hour with electrolyte. This suggests a strong autocatalytic effect during oxygen removal. In such reactions, a product also acts as a catalyst, causing the rate to increase as the reaction proceeds—as seen in acid-catalyzed ester hydrolysis and liquid-phase crystallization21,22. For comparison, pure iron shows a continuous rate decline to near zero under both conditions. Reduced iron behaves similarly under non-saline conditions, but under saline conditions, it displays a V-shaped curve: the rate drops sharply in the first 2 hours, then gradually rises. The X-ray diffraction (XRD) results in Supplementary Fig. 2 show that Fe3O4 and FeO(OH) are simultaneously formed during the reaction. At the early stage (2 hours), Fe3O4 dominates, leading to a relatively low oxygen removal rate. With continued reaction, the FeO(OH) phase progressively increases and becomes pronounced at 6 and 8 hours, giving rise to the V-shaped variation in Fig. 1g. The scanning electron microscopy (SEM) images shown in Supplementary Fig. 3, together with the energy-dispersive spectroscopy (EDS) maps in Supplementary Fig. 4, further corroborate the result.

Record-high oxygen removal capacity
Fig. 2a compares the oxygen removal time and percentage for the three materials, underscoring the superior performance of FeSiB MG. To quantify this, we integrated the instantaneous rate curves from Fig. 1f,g and divided by the reaction time to obtain the average rate ka. As shown in Fig. 2b, under non-saline conditions, the ka of FeSiB MG is 60 times that of pure iron and 41 times that of reduced iron powder; under saline conditions, it remains 40 and 9 times higher, respectively.

Besides reaction rate, oxygen removal capacity is another key metric for evaluating scavenger performance. To assess it more accurately, we used 0.5 g of sample and increased the air volume to 1200 mL to ensure sufficient moisture and oxygen. Based on their iron mass fraction (FeSiB MG: 91.7%, pure iron: 100%, reduced iron: 98.8%), the theoretical maximum oxygen removal capacities at 298 K are 1.436, 1.566, and 1.547 L, respectively.

Fig. 2c compares the equivalent oxygen removal capacities—defined as the volume of air from which oxygen is removed—at 12, 24, and 48 hours, relative to theoretical limits. In practical use, performance within 12 hours is most critical. In 12 hours, 1 g of FeSiB can remove oxygen from 1.045 L of air, approaching its theoretical maximum and far exceeding pure iron (0.149 L) and reduced iron (0.440 L). After 24 hours, FeSiB reaches 1.439 L g-1, reaching its Fe-based theoretical limit, and further increases to 1.596 L g-1 at 48 hours—surpassing even the theoretical limit of pure iron (1.566 L g-1). The highly reactive Fe atoms in FeSiB promote the synergistic involvement of Si in the reaction, a phenomenon first reported here (Supplementary Fig. 5).

To comprehensively compare material performance, a radar chart (Fig. 2d) was constructed using ka, and weight-, cost-, and area-normalized equivalent oxygen removal capacities (12- and 24-hours). Given the porous nature of reduced iron powder, specific surface areas were measured via the BET method. FeSiB MG outperforms reduced iron powder across all metrics, delivering much higher oxygen removal rates and capacities despite having less than one-tenth of the surface area. Owing to its low material and processing costs, FeSiB MG also shows superior cost-effectiveness—approximately 2.3× higher than reduced iron based on 12-hour performance (Supplementary Fig. 6). Moreover, as Fe-based MGs do not require specific formability, thickness, or magnetic properties for use as oxygen scavengers, processing costs are expected to decrease further.

The oxygen removal performance of FeSiB MG can be further improved. Pre-reacting 2.1 g of FeSiB powder with oxygen to consume 0.1 g significantly enhances its activity. This modified material is referred to as pre-reacted FeSiB (see Methods for details). Additionally, atomized amorphous powders Fe78Si9B13 (denoted as FeSiB-2) and Fe77.3Si6.3B13.9C2.6 (FeSiBC) with smaller particle sizes show markedly improved performance, removing >99.7% of oxygen from 500 mL of air within just 1.6 and 2.0 hours, respectively. Such rapid kinetics demonstrate its potential for oxygen potential regulation.

Fig. 2e compares the oxygen removal rates of Fe-based MG scavengers from this study with various reported systems8,11,23-30. For reliable comparison, all rates here were calculated as volume of oxygen removed per unit time and weight. The results show that Fe-based MGs outperform all others by 1-4 orders of magnitude in oxygen removal rate.

Low-temperature and long-term storage performance
In practical applications, Fe-based oxygen scavengers are typically operated within a temperature range of 288-303 K. For conventional reduced iron powders, decreasing temperature suppresses the reaction kinetics of oxygen consumption, rendering them largely ineffective below approximately 283 K. To systematically evaluate the low-temperature adaptability of FeSiB MG and reduced iron powder, comparative oxygen scavenging experiments were therefore conducted at 278 K.

As shown in Fig. 3a, the oxygen absorption performance of conventional reduced iron powder deteriorates substantially under low-temperature conditions: only about half of the oxygen is consumed within 24 h, which is insufficient to meet the preservation requirements in food and pharmaceutical packaging. In contrast, the FeSiB oxygen scavenger maintains a high oxygen removal rate at 278 K and is capable of completely depleting the oxygen in a sealed container within 15 h. These results demonstrate that the FeSiB MG scavenger effectively overcomes the low-temperature performance limitations inherent to conventional iron-based systems.

The kinetic fitting results in Fig. 3b further reveal that the FeSiB MG retains an autocatalytic reaction behavior even at low temperature, whereas no such characteristic is observed for reduced iron powder. This sustained autocatalytic feature under low-temperature conditions accounts for the superior oxygen removal performance and substantially broadens the applicable temperature window of Fe-based oxygen scavengers.

In addition to operational performance, long-term storage stability is a critical consideration for practical deployment, as oxygen scavengers are commonly stored in sealed environments for extended periods prior to use. To assess storage stability, the as-prepared FeSiB scavengers were sealed in 10 mL centrifuge tubes and stored at room temperature for 30 days before oxygen scavenging measurements were conducted. As shown in Fig. 3c, no noticeable degradation in oxygen removal performance is observed after storage, indicating that prolonged sealing does not induce surface passivation of the MG. This long-term retention of reactivity highlights the robustness of the FeSiB scavenger and underscores its suitability for applications requiring both low-temperature operability and extended shelf life.

Atomic-scale insights from DFT
To better understand the exceptional oxygen removal performance of FeSiB MG, we simulated the O2 molecule adsorption process on its surface in the presence of H2O molecules and compared it with that on the body-centered cubic (BCC) Fe(110) surface—the most stable and densely packed surface of BCC Fe31. Using climbing image-nudged elastic band (CI-NEB) calculations based on DFT, we estimated the transition states and energy barriers for O2 adsorption. The energy barrier in the pure Fe case is 3.39 eV, while in the FeSiB MG case it is only 1.29 eV (Fig. 4a; transition states in Fig. 4b; full structures in Supplementary Fig. 7), indicating a much easier O2 adsorption process on FeSiB MG and explaining its superior oxygen removal activity.

We have also calculated the energy barriers of the O2 adsorption process by using the implicit solvent model to include the effect of the NaCl electrolyte. It should be noted that the possible specific effects of chloride ions were not considered in this model. The FeSiB MG still shows a lower energy barrier and therefore easier O2 adsorption (Supplementary Fig. 8a). Besides, the O2 adsorption process on the diamond-structured pure Si(111) surface and Si sites on the FeSiB MG surface were also calculated, with and without considering implicit solvation effects. The results show lower energy barriers of the O2 adsorption on both the pure Si and Si atom in FeSiB MG (see Supplementary Figs. 9-12 for more details), supporting that the Si can actively react with O2. However, in bulk crystalline Si, the formation of a surface Si oxide layer prevents the inner Si atoms from reacting with oxygen, whereas in FeSiB MG, the preferential oxidation of Fe promotes the oxidation of Si and maintains the exposure of active sites. The role of Si will be discussed in detail in the following section.

According to energy band theory, the adsorption process involves the hybridization of Fe 4s and 3d orbitals with O orbitals, forming bonding and antibonding states. This interaction leads to electron rearrangement, changes in charge density, bond breaking (O-O), and bond formation (Fe-O)32,33. Since the Fe 4s orbitals are broad in the energy and their projected density of states (PDOS) is much smaller than Fe 3d orbitals (see Supplementary Fig. 13), the primary effects arise from the hybridization between O and Fe 3d orbitals34. The overall energy change in this process can be effectively described by the Fe d-band center (see Methods section). An upward shift of the Fe d-band center strengthens the Fe–O interaction by reducing the occupation of Fe–O antibonding states, which facilitates electron transfer into the O antibonding orbitals, weakens the O–O bond, and ultimately promotes O2 dissociation35-38, as shown in Supplementary Fig. 14. This d-band center theory has been successful in describing transition metal surfaces39-42.

In our results, the PDOS for the 3d orbitals of surface Fe atoms before O2 adsorption was obtained, and the corresponding d-band centers were calculated (Fig. 4c). FeSiB MG shows a higher d-band center at -1.55 eV compared to -1.85 eV for pure Fe, which explains its stronger O2 adsorption. The pure Fe value closely matches the reported value of -1.80 eV43, confirming the result of our calculation. The higher d-band center of FeSiB MG is also confirmed in the calculation with implicit solvent model (Supplementary Fig. 8b). To further understand the stronger adsorption, the charge density difference around the O2 molecule in the initial states (Fig. 4d) is presented. For FeSiB MG, there is a decrease in charge density between the O atoms and an increase around them, indicating a stronger tendency for O-O bond breaking. In contrast, O2 on pure Fe shows a decrease in overall charge density with no significant O-O bond breaking, consistent with its lower d-band center and higher adsorption energy barrier. Overall, DFT calculations reveal a low energy barrier for O2 adsorption on FeSiB MG, explaining its exceptional oxygen removal activity on the atomic scale.

Origin of robust autocatalytic effect
Based on the experimental data shown in Figs. 1b and 1c, the correlation curves between the oxygen removal kinetics and the mass of reaction products under the two conditions were constructed (see Supplementary Figs. 15a,b). The evolution trends of these curves indicate that, the oxygen removal process exhibits a typical autocatalytic behavior, characterized by a rapid acceleration of the reaction rate with increasing product formation. To probe the mechanism of autocatalytic behavior, we analyzed the reacted composite powder under saline conditions. The reacted samples were washed with ethanol to remove loosely bound iron oxides and part of residual diatomite, then dried and characterized by XRD, as shown in Fig. 5a. Due to interference from diatomite and moisture, reliable and systematic information could not be readily obtained from operando XRD measurements; therefore, the reaction products were subjected to post-treatment.

XRD analysis reveals distinct oxidation behavior of FeSiB MG. The reaction products consist mainly of diatomite and residual amorphous phase. γ-FeO(OH) is identified as the primary oxidation product, though its weak diffraction intensity suggests poor adhesion to the MG matrix, with most oxides removed during washing. This facilitates continuous exposure of active sites, which is essential for sustained oxygen scavenging. Poor adhesion and easy spallation of FeO(OH)-type oxides are widely recognized and well documented in corrosion science and oxidation literature20,44. XRD pattern (Supplementary Fig. 16) and high-resolution transmission electron microscopy (HRTEM) image (Supplementary Fig. 17) of the separated orange-red products further confirm γ-FeO(OH) as the dominant oxidation species. In contrast, pure iron and reduced iron exhibit markedly different oxidation behavior. Post-reaction XRD pattern shows dominant Fe3O4 along with minor γ-FeO(OH) and α-FeO(OH), indicating sluggish kinetics in crystalline iron that lead to incomplete oxidation and passivating Fe3O4 formation. These results underscore the fundamental contrast between FeSiB MG and crystalline iron. DFT calculations provide mechanistic insight: the strong oxygen adsorption and dissociation abilities of FeSiB enhance surface reactivity, enabling complete oxidation and suppressing Fe3O4 formation.

To elucidate the autocatalytic mechanism of FeSiB MG, we conducted microscopic characterization of the reacted powder. SEM and EDS mapping images (Fig. 5b-d) reveal a coupled microstructure of diatomite (cyan) and nano iron oxides (red) on the particle surface. This interfacial structure is key to enhanced oxygen removal. Such regions are characteristic of the post-reaction particles, as illustrated in Supplementary Fig. 18. BET analysis shows the oxidation products (including adhered diatomite) possess a high specific surface area of 121 m2 g-1, far exceeding that of pristine diatomite (1.65 m2 g-1; Supplementary Fig. 19). These findings, along with oxygen removal data, clarify the autocatalytic behavior of FeSiB MG.

As illustrated in Fig. 5e, the initial oxygen removal by FeSiB MG is driven by surface adsorption of O2 and H2O, with diatomite providing moisture to sustain the reaction. Over time, a nanoporous γ-FeO(OH) layer rapidly forms, coupling with diatomite to create a hierarchical interfacial structure. This architecture promotes reactant transport, prevents surface passivation to maintain active site exposure, and provides stable interfaces for electron transfer. As the reaction progresses, the evolving porous nano-oxide layer further refines the interface, underpinning the observed autocatalytic behavior. This stands in stark contrast to that of crystalline iron.

Autocatalytic reactions commonly show slow initial rates because of low product concentrations21,22. In contrast, FeSiB MG deviates fundamentally from this conventional pattern: its amorphous structure enables high intrinsic reactivity from the onset.

Prior studies show that Fe2+ and Fe3+ species in Fe(OH)2 and FeO(OH) can reorganize into Fe3O445, but FeSiB MG—with its superior oxygen adsorption and dissociation capabilities—undergoes complete oxidation, effectively avoiding Fe3O4 formation. Its highly adsorptive surface layer further promotes oxygen transport, ensuring full utilization of Fe. These findings align with reports linking Fe3O4 formation to Fe(OH)2 oxidation46 and its possible transformation into γ-FeO(OH) and α-FeO(OH) under suitable conditions47, offering a mechanistic basis for the distinct reactivity of FeSiB MG.

A simple experiment confirms the strong link between FeSiB MG’s autocatalytic effect and its surface structure. Pre-reacting the powder to form a dual-zone interface—comprising a water-retention zone and a strong adsorption zone—significantly enhanced oxygen removal, reducing the complete oxygen removal time from 5.6 to 3.5 hours (Supplementary Fig. 20).

Analysis of oxidation behavior
To elucidate the oxidation mechanism of the FeSiB MG oxygen scavenger, a series of controlled experiments was designed. Fig. 6a compares the Fe 2p3/2 X-ray photoelectron spectroscopy (XPS) spectra of the native oxide layers formed on FeSiB MG and pure Fe. The FeSiB sample exhibits a higher initial oxidation state of Fe, indicating a stronger intrinsic affinity for oxygen.

To isolate the contribution of Si, additional experiments were conducted in the absence of diatomite. Specifically, 2 g of FeSiB powder was mixed with 30 μL of 1 wt% NaCl solution and allowed to react under ambient air. After 1 h, an additional 30 μL of solution was introduced, and this procedure was repeated multiple times. Samples subjected to n cycles were denoted as FeSiB-Rn. The small volume of electrolyte was deliberately chosen to achieve micro-wetting without full immersion, ensuring that oxygen uptake occurred at the solid–gas–liquid interface rather than via bulk solution reactions. This condition is critical for effective oxygen scavenging.

XPS spectra were first detected for samples subjected to 10, 20, and 30 reaction cycles. The relative fractions of Si oxides and Fe oxides in the resulting surface oxide layers were quantified and compared with those of the native oxide on the as-prepared alloy, as well as with the nominal bulk composition. The XPS spectra of Si and Fe oxides are shown in Supplementary Figs. 21 and 22, respectively.

The results are summarized in Fig. 6b. Notably, the native oxide layer on FeSiB MG is already strongly enriched in Si oxides relative to the nominal composition, indicating a pronounced oxygen affinity of Si, in good agreement with the DFT predictions. More importantly, the Si-to-Fe oxide ratio increases monotonically with progressive oxidation. As shown in the XPS survey spectra in Supplementary Fig. 23, the signal corresponding to oxidized Si is clearly pronounced. This trend provides compelling evidence for the active participation of Si in the oxygen scavenging process; in the absence of a significant Si contribution, continued oxidation of Fe would be expected to yield a surface dominated by Fe oxides, thereby precluding any further increase in the relative Si content.

Figs. 6c and d show the XRD patterns of reacted FeSiB and pure Fe samples from the diatomite-free experiments. To exclude thermal effects, all samples were dried naturally at room temperature. In the FeSiB series, the diffraction features are weak due to the poor crystallinity of the oxidation products; nevertheless, the characteristic reflections of γ-FeO(OH) are discernible in the FeSiB-R20 sample. In contrast, for pure Fe, the formation of Fe3O4 is detected after only two reaction cycles. These observations are fully consistent with the above XRD results.

To further quantify the oxidation degree and Fe–O coordination environment in the FeSiB MG and pure Fe, synchrotron-based X-ray absorption measurements were performed on samples reacted for the same duration (5.5 h). Fig. 6e presents the Fe K-edge X-ray absorption near edge structure (XANES) spectra of FeSiB before reaction, FeSiB after reaction, and reacted pure Fe. As the absorption edge position reflects the Fe oxidation state, the edge of reacted pure Fe (blue curve) is clearly shifted to lower energy relative to that of reacted FeSiB (red curve), confirming a lower average oxidation state. Moreover, the pronounced intensity differences highlighted by the red arrow indicate a higher oxidation degree in FeSiB MG.

Fig. 6f shows the corresponding extended X-ray absorption fine structure (EXAFS) spectra (phase shift not corrected) in R space, which provide insight into the local Fe–O coordination. Comparison of the pristine alloy (black) and reacted FeSiB (red) confirms that the post-reaction spectra are not significantly influenced by residual Fe coordination in the MG. The FeSiB scavenger exhibits a broadened first-shell Fe–O contribution (R ≈ 1.3–1.5 Å), accompanied by a weak, continuous second-shell feature (R ≈ 2.6–2.9 Å), while higher-shell contributions are largely suppressed. This coordination signature is characteristic of low-crystallinity Fe oxyhydroxide species closely resembling γ-FeO(OH).

In contrast, the crystalline Fe-based scavenger displays a different EXAFS profile, with a strong first-shell Fe–O peak at 1.1–1.5 Å and a pronounced second-shell feature at 2.6–2.9 Å, together with retained medium-intensity signals in the 3.5–4.5 Å range. These features are indicative of a mixed coordination environment dominated by Fe3O4, with additional contributions from FeO(OH). A weak feature at ~2.3 Å suggests a minor fraction of residual metallic Fe. Notably, the intensity observed around 1.1–1.2 Å does not correspond to an independent coordination shell but arises from the low-R extension of the first-shell Fe–O contribution, a common characteristic of Fe–O-based systems. This effect is intrinsic to both iron oxides and oxyhydroxides and is further influenced by phase shifts, window functions, and multiple-scattering contributions.

Taken together, the XANES and EXAFS results consistently demonstrate that Fe in the FeSiB MG is oxidized more readily and to a higher degree than in crystalline Fe, corroborating its superior oxygen scavenging capability.

Analysis of the contribution of Si
To evaluate the contribution of Si in the FeSiB MG, SEM observation was performed on the FeSiB-R20 sample prepared without diatomite to eliminate interference. As shown in Fig. 7a, the reacted FeSiB-R20 exhibits a highly porous surface morphology, with a large fraction of oxidation products appearing as delaminated or exfoliated features. The corresponding EDS elemental maps (Fig. 7b-e) acquired from the region highlighted in Fig. 7a show pronounced enrichment of Fe and O within the oxide layer, accompanied by a clear Si signal, confirming the involvement of Si in the oxidation process. The EDS spectrum (Fig. 7f) yields an average composition of Fe31.77Si2.74O65.49 (at%), corresponding to a Si-to-Fe atomic ratio of 8.62%, slightly lower than the nominal value of 11.54%. Assuming the oxidized Si is present as SiO2, the estimated contribution of Si to oxygen uptake reaches ~11.49% for controlled experiments without diatomite. Considering the presence of intermediate Si oxidation states, the actual contribution is expected to be close to but slightly lower than this value. It should be noted that the removal of diatomite in this experimental series may lead to minor variations in the apparent Si contribution compared with diatomite-containing systems. Nevertheless, these results unambiguously demonstrate the active role of Si in oxygen scavenging and provide a reasonable quantitative estimate of its contribution.

Raman and infrared spectroscopy were also employed to probe the oxidation behavior of Si (see Supplementary Figs. 24 and 25); however, their phase discriminability was limited. On one hand, the presence of Fe–Si and Fe–B bonding in the FeSiB alloy gives rise to multiple intrinsic vibrational features that complicate spectral assignment. On the other hand, the poor crystallinity of the oxidation products leads to significant peak broadening, further reducing spectral resolution. Nevertheless, both Raman and infrared spectra clearly reveal the formation of γ-FeO(OH) and α-FeO(OH), with γ-FeO(OH) being the dominant phase, in good agreement with the XRD results.

Methods
Materials
The flaky FeSiB and FeSiBNbCu amorphous powders used in the experiments were purchased from Qingdao Yunlu Advanced Materials Technology Co., Ltd. (China) and prepared using the airflow crushing method. The subglobular Fe78Si9B13 (prepared by gas-water atomization) and spherical Fe77.3Si6.3B13.9C2.6 (prepared by gas atomization) amorphous powders were purchased from Chengdu Ketailong Alloy Co., Ltd. Pure iron powder was purchased from Hebei Chuangying Metal Materials Co., Ltd. (China) and prepared by the gas atomization method, with Fe content > 99.9 wt%. The reduced iron powder (composition: Fe 98.8, Mn 0.4, Cr 0.2, Si 0.2, S 0.2, Ca 0.1, Al 0.1, wt%) was secondary reduced iron powder, purchased from Tianjin Beichen District Fangzheng Reagent Factory (China). The diatomite (300 mesh, composition: (SiO2) 92.5, (Al2O3) 3.6, (Na2O) 2.7, (Fe2O3) 1.2, wt%) used for the oxygen removal experiments was sourced from Henan Boxu Environmental Protection Technology Co., Ltd. (China). The water used in the experiments was obtained from an ultrapure water system, and the 1% NaCl saline solution was prepared using analytical-grade NaCl (China National Pharmaceutical Group Chemical Reagent Co., Ltd.) and ultrapure water.

In the preparation of FePC ribbons, pure iron (>99.95 wt%), ferrophosphorus (22 wt% P), and carbon particles (>99.9 wt%) were weighed according to the nominal composition and melted five times into button ingots using a non-consumable vacuum arc furnace under argon protection. The ingots were then cut and rapidly quenched into ribbons using a vacuum melt-spinner (copper roller speed: 40 m s-1). The amorphous ribbons were vacuum-annealed (pressure < 5 × 10-3 Pa) at 623 K for 1 hour, then ground for 3 min using a commercial grinder and sieved through a 100-mesh screen.

Sample characterization
A Co-source diffractometer (D8 Advance X, Bruker, Germany) and a Cu-source diffractometer (SmartLab, Rigaku, Japan) were used to analyze the phase information of samples. The scanning rates were 10° min-1 and 5° min-1, respectively. The XRD results for the starting metal powders are shown in Supplementary Fig. 27a. HRTEM and selected-area electron diffraction (SAED) of the FeSiB powder were performed using a Talos F200x TEM (FEI, USA), with representative HRTEM images shown in Supplementary Fig. 27b. The reaction products were added into 20 mL of anhydrous ethanol, and after filtration through a 0.22 μm filter membrane, the samples containing nano-iron oxide particles were subjected to TEM observation. SEM (GeminiSEM 300, ZEISS, Germany) equipped with an energy dispersive spectrometer was used for sample observation and analysis. The poorly conductive powders were priorly sputter-coated with platinum. All the SEM observations were repeated three times, yielding similar results. Particle size distributions of the Fe-based MGs, pure iron, and reduced iron powders were measured using a laser particle size analyzer (Mastersizer 3000, Malvern, UK). The BET specific surface area of the samples was tested using a fully automated surface area and porosity analyzer (ASAP 2460, Micromeritics, USA). A Raman spectrometer (LabRAM HR Evolution, Horiba, Japan) and a Fourier transform infrared spectroscopy (FT-IR, RTracer-100, SHIMADZU, Japan) were used to analyze the reaction products. Prior to the FT-IR measurement, the samples were dried at 393 K for 5 min to remove moisture. Compositions on the oxide films of initial and reacted FeSiB samples were measured by an X-ray photoelectron spectroscopy (XPS; Scientific K-Alpha, Thermo Fisher, USA), with charge correction referenced to the C 1s peak at 284.8 eV. The XAFS spectra of reacted FeSiB and Fe samples were measured at the Energy Materials Beamline (hard branch) of the Shanghai Synchrotron Radiation Facility (SSRF) to analyze the oxidation degree and Fe–O coordination environment. For sample preparation, 5 g of the reacted scavenger was vacuum-dried and then milled in a planetary ball mill for 2 hours using a ball-to-powder weight ratio of 6:1. ZrO2 milling balls with a diameter of 5 mm were employed, and 8 mL of ethanol was used as the milling medium. After milling, the powder was dried at 393 K and subsequently sieved through a 400-mesh screen; the collected fine fraction was used for XAFS measurements.

Oxygen removal performance testing
Each oxygen removal experiment was conducted as follows: 0.8 g of diatomite was weighed and added to a 50 mL polypropylene tube, followed by 1 mL of ultrapure water or 1 wt% NaCl solution. The mixture was stirred for 1 min using a polystyrene rod to ensure uniform wetting. Fe-based powder (2 g for rate testing or 0.5 g for capacity testing) was then added and stirred for another minute to ensure thorough mixing. The diatomite dosage of 0.8 g was optimized through preliminary experiments. Routine experiments were conducted at 298 K, while low-temperature experiments were performed at 278 K in a temperature-controlled refrigerator. All measurements for each material were obtained from the same sample, with three samples included in each experimental group, and all experiments exhibited good reproducibility. In the long-term storage experiment, each prepared mixed sample consisting of 2 g of FeSiB powder, 0.8 g of diatomite, and 1 g of saline solution was sealed in a 10 mL centrifuge tube, which was subsequently stored in a vacuum bag. After 30 days, the samples were taken out and subjected to oxygen removal experiments.

The mixed powder was placed in a 70 mm glass Petri dish and immediately transferred to a transparent sealed chamber equipped with an oxygen detector (accuracy: 0.1% VOL, Nanjing Yice Technology Co., Ltd., China). A camera recorded the real-time change in oxygen concentration. When the reading reached 0, the actual oxygen concentration was < 0.05%, corresponding to an oxygen removal efficiency > 99.7%. The sealed chamber had a volume of 560 ± 10 mL for rate testing and 1260 ± 15 mL for capacity testing, measured by water displacement. The Petri dish and detector occupied ~60 ± 5 mL. The recorded videos were analyzed to extract oxygen concentration data over time, enabling evaluation of oxygen removal rate and capacity.

After rate testing, the reacted powders were cleaned by dispersing in 20 mL anhydrous ethanol in a 50 mL beaker, shaking for 20 s, and separating using a magnet. The cleaning process was repeated three times. The powders were then dried on filter paper on a 373 K hot plate for subsequent characterization. In one experiment, the ethanol suspension from washing the FeSiB reaction products was transferred to a 200 mL beaker and left to settle for 1 min. The supernatant was decanted, and the remaining powder was dried at 373 K, yielding iron oxide composite powders with residual diatomite. In the pre-reaction experiment of the FeSiB MG oxygen scavenger, the powder mass was increased from 2.0 to 2.1 g, with all other conditions identical to the standard saline tests. When the oxygen concentration dropped to 15.4%, approximately 0.1 g of FeSiB was fully oxidized, at which point the reaction vessel was opened to restore oxygen levels. To compensate for slight moisture loss during pre-reaction, water was replenished based on the measured weight reduction in the Petri dish before conducting subsequent oxygen removal tests.

DFT calculations
Our spin-polarized first-principles DFT calculations for pure Fe and FeSiB MG were carried out by the Vienna ab initio simulation package (VASP) version 5.4.448-51. The Perdew-Burke-Ernzerhof (PBE) functional in the generalized gradient approximation (GGA) was employed to describe the exchange-correlation functional52, and the projector augmented-wave (PAW) method with a plane wave basis set was used to model the core-valence electron interactions with an energy cutoff of 500 eV for both calculations. Due to the relatively large simulation cells, the k-points sampling of the first Brillouin zone was carried out using a 2 × 2 × 1 Gamma-centered mesh. To accurately treat the 3d orbitals of Fe atoms, we applied the empirical simplified (rotationally invariant) DFT+U approach with an effective U value (Ueff) of 4.3 eV53-55. The DFT-D3 corrections were used to account for van der Waals interaction56. Electronic self-consistency was achieved when the energy change was less than 10-5 eV. For geometry optimization, the systems were relaxed until the norms of all the forces were smaller than 0.05 eV·Å-1. The BCC Fe slab with the (110) surface exposed was modeled as a BCC structure with 4 layers, and each layer contains 3 × 4 supercells with 2 atoms per supercell (24 atoms per layer). While the Fe-based metallic glass slab with 75 Fe atoms, 12 B atoms and 9 Si atoms was generated using ab initio molecular dynamics (AIMD) method with NVT ensembles of Nose-Hoover thermostats under 1600 K for 2 ps with a timestep of 2 fs. A vacuum layer of 12 Å in the z direction was added to the slabs to prevent interactions between the neighboring slabs, and two H2O molecules were attached to the surfaces of the slabs in both calculations. Then, one O2 molecule or two O atoms were attached to the surface as the initial state model or final state model in both calculations. The structures of these models were then optimized by the conjugate gradient method. The path and the energy barriers of the O2 adsorption were then calculated using the climbing image nudged elastic band (CI-NEB) method, which had been implemented in the VASP transition state tools (VTST)57,58.

The Fe d-band center (εd) was defined as Equation (2):
εd = (∫_{-∞}^{∞} PDOS(ε)·ε·dε) / (∫_{-∞}^{∞} PDOS(ε)·dε) (2)
where PDOS(ε) is the projected density of states of Fe d orbitals and ε is the energy.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript presents a compelling study on Fe-based metallic glasses as ultra-efficient oxygen scavengers. It\naddresses long-standing limitations of conventional systems by demonstrating unprecedented oxygen removal rates and\ncapacities to be further used in gas purification, chemical stabilization, and catalytic processes.\nBefore publication, there are some improvements needed in the following parts:\n1) The V-shaped profile in a saline environment needs to be better explained. Authors have stated that “…the rate drops\nsharply in the first 2 hours, then gradually rises. This is likely due to two synergistic effects—NaCl suppresses surface\npassivation, and the porous structure enhances reactant transport and active surface exposure.” Authors are strongly\nencouraged to perform SEM-EDX or any other surface-sensitive analysis to prove this phenomenon.\n2) The experiments were performed on a rather short experimental frame, whereas real applications may require months-\nlong scavenging activity. The authors need to perform longer-term (e.g., a week) tests with FeSiB MG to ensure that the\nmaterial can resist long-term exposure to solvents with acceptable oxygen evolution rates.\n3) Theoretical oxygen removal performance was assessed only on Fe content but ignores potential Si contribution, even\nthough it can enhance the glass forming ability. What is the main reason behind not using Si in the calculations?\n4) No elemental mapping was presented to confirm how oxides are distributed. More importantly, a single micrograph was\nprovided to infer the general morphology, but this may not be so representative. Authors are expected to give a low-\nmagnification image with elemental mapping and/or indicate diatomite (green) and iron oxide (red) regions\n5) Despite the high performance and scalability of Fe-based metallic glasses as oxygen scavengers, translating their\nlaboratory-scale success into real-world industrial applications poses challenges. Authors are expected to acknowledge this\nchallenge and present a forward-looking statement on how to address it", "reviewer_2": "The manuscript entitled \"Fe-based Metallic Glasses as Ultra-efficient Oxygen Scavengers\" claims to report Fe-based\nmetallic glasses (MGs) with superior oxygen-scavenging performance, exceeding conventional materials by 1–4 orders of\nmagnitude. While the topic is industrially relevant, the work suffers from several critical flaws. The detailed comments and\nsuggestions are in below:\n1. The authors state that FeSiB MG, pure iron, and reduced iron have \"matched volumetric particle sizes\" (Supplementary\nFig. 1), but reduced iron exhibits a porous structure with a specific surface area (0.412 m²/g) over 12 times higher than FeSiB\nMG (0.0340 m²/g). This drastic difference in surface area—known to dominate reaction kinetics in redox processes—\ninvalidates direct comparisons of \"intrinsic reactivity.\" Why was reactivity not normalized by surface area to isolate the effect\nof amorphous structure?\n2. The 48-hour capacity of FeSiB MG (1.596 L/g) is claimed to \"surpass the theoretical limit of pure iron (1.566 L/g)\". This is\nphysically implausible unless Si participates in oxygen scavenging, but the authors provide no stoichiometric basis for Si\noxidation (e.g., 4Fe + 3O₂ → 2Fe₂O₃ vs. Si + O₂ → SiO₂). XPS (Supplementary Fig. 2f) shows Si⁴+ but no quantification of\nSi-derived oxygen uptake. Without this, the \"synergistic activation of Si\" remains speculative.\n3. The oxygen adsorption energy barrier (1.29 eV for FeSiB vs. 3.39 eV for crystalline Fe) is computed using a static slab\nmodel with 2 H₂O molecules, which fails to replicate the saline/ moist environment of the experiments. Realistic conditions\ninvolve electrolyte (NaCl) and dynamic water layers, which can drastically alter surface energetics. Why were these factors\nexcluded?\n4. XRD identifies γ-FeO(OH) as the primary oxidation product, but Raman spectra (Supplementary Fig. 2e) show no distinct\npeaks for this phase, and TEM images of the oxide layer are absent. The claim that γ-FeO(OH) \"poorly adheres to the MG\nmatrix\" is unsupported—how was adhesion quantified?\n5. Autocatalysis requires a product to accelerate the reaction, but the authors attribute it to \"nanoporous γ-FeO(OH) +\ndiatomite\" without kinetic evidence (e.g., rate vs. product concentration plots).\n6. The \"1–4 orders of magnitude higher rate\" (Fig. 2e) compares FeSiB to systems like glucose oxidase and tocopherol,\nwhich operate via entirely different mechanisms (enzymatic vs. redox). A fair comparison would include state-of-the-art Fe-\nbased scavengers (e.g., nano-Fe@C composites), but these are omitted. Why?\n7. Error bars in Figs. 1b,c are small (±0.02%), but the authors report \"n=3\" without details on reproducibility. Given the high\nvariability in powder-based reactions, were replicate experiments conducted with different batches of materials?\n8. The DFT calculations (page 9) simulate O₂ adsorption on static surfaces with 2 H₂O molecules, ignoring the role of NaCl\nelectrolyte (critical for enhancing kinetics, Fig. 1c). How do Cl⁻ ions affect O₂ adsorption energy barriers or Fe d-band\ncenters? Would a more realistic electrolyte-inclusive model alter the proposed atomic-scale mechanism?\n9. The manuscript focuses on short-term performance (≤48 hours), but practical applications require long-term stability. Does\nFeSiB MG undergo passivation over extended use (e.g., 1 week), and if so, what is the mechanism (e.g., crystalline oxide\nlayer formation)? Can the scavenger be regenerated (e.g., via reduction) without losing activity?\n10. While FeSiB, FePC, and FeSiBC are tested (Supplementary Fig. 9), the correlation between MG composition (e.g.,\nB/Si/C content) and oxygen-scavenging performance is unexplored. For instance: Does increasing Si content systematically\nenhance capacity, or is there a critical threshold? How do alloying elements (e.g., Nb, Cu in FeSiBNbCu) influence\noxidation kinetics?\n11. The experiments are conducted at 298 K, but real-world applications involve variable temperatures/humidity. How does\nperformance degrade at extreme conditions (e.g., <273 K or >333 K, low relative humidity)? Does the amorphous structure\nremain stable under these conditions, or does devitrification occur, altering reactivity?\n12. The cost analysis (Supplementary Fig. 3) compares raw material prices but ignores processing costs (e.g., gas\natomization for FeSiB-2). How does scalability (e.g., ton-scale production) affect cost, and can Fe-based MGs compete with\nestablished low-cost scavengers (e.g., reduced iron) in high-volume applications (e.g., food packaging)?\n13. The manuscript suggests applications in \"gas purification\" and \"semiconductor manufacturing\" (p. 22) but provides no\ndata on compatibility with these systems. For example: Does the scavenger release toxic byproducts (e.g., B oxides) that\ncould contaminate semiconductor environments? How does it perform in gas streams with impurities (e.g., CO₂, H₂S)\ncommon in industrial settings?\n14. Some suggestions are provided: 1) To validate the Role of Amorphous Structure in Oxygen Adsorption, In-situ X-ray\nAbsorption Fine Structure (XAFS) should be conducted. comparing Fe’s coordination in amorphous vs. crystalline Fe\nbefore/after reaction would reveal whether the amorphous structure promotes more labile Fe-O bonding, supporting DFT\nclaims of lower adsorption barriers. 2) Quantifying Si’s Synergistic Oxidation, in-situ Raman Spectroscopy with Isotopic\nLabeling should be useful. Using 18O2 instead of ambient 16O2 during reactions, combined with in-situ\nRaman, can distinguish O incorporation into Fe oxides vs. Si oxides (via shifted vibrational modes of 18O2-containing species). 3) To\nverify Long-Term Stability and Practical Viability, the authors can conduct Operando XRD under Humid/Saline Conditions.\nExisting XRD characterizes post-reaction products, but operando XRD would track oxide phase evolution (e.g., γ-FeO(OH)\nvs. passivating Fe₃O₄) in real time under moist/saline conditions. 4) To probe the Autocatalysis and Oxide Adhesion, In-situ\nAtomic Force Microscopy (AFM) with Nanomechanical Mapping can be performed. Measuring the force required to detach\noxide nanoparticles from the MG surface (vs. crystalline Fe) would experimentally validate claims that γ-FeO(OH) “poorly\nadheres” to the MG matrix, sustaining active sites.\nGiven the current work’s focus on applied performance and limited mechanistic depth—coupled with the need for further\nvalidation of core claims, this manuscript may be better suited for journals emphasizing materials applications rather than\nfundamental science. Journals such as ACS Applied Materials & Interfaces or Journal of Materials Chemistry A would\nprovide a more appropriate venue."}, "author_response": "Response Letter to Reviewers\nWe sincerely thank the reviewers for their careful assessment of our manuscript and for\ntheir constructive and insightful comments. We have revised the manuscript extensively in\nresponse, resulting in substantial improvements in both scope and clarity.\nIn the revised version, the number of figures in the main text has been increased from 4 to\n7, and the Supplementary Information has been significantly expanded, with the number of\nsupplementary figures increasing from 10 to 27. Three additional sections (low-temperature\nand long-term storage performance, analysis of oxidation behavior, analysis of the\ncontribution of Si) have been added to the main text. Owing to space constraints in the main\ntext, most added data and detailed analyses are presented in the Supplementary Information.\nAll the revisions in the main text have been marked with yellow background.\nThe major revisions are summarized below:\n Six new DFT calculations were performed, establishing the high reactivity of Fe and Si\nin FeSiB MG under solvation conditions.\n The role of Si was systematically investigated and clarified through a combined DFT–\nexperimental framework.\n New low-temperature experiments were conducted, demonstrating the unique\nperformance advantage of FeSiB MG scavenger at low temperature.\n Long-term storage experiments were added, confirming the absence of passivation and\nsustained oxygen-scavenging performance for FeSiB.\n Control experiments of samples without diatomite were conducted to exclude potential\ninterference from the diatomite component.\n Additional XPS, XRD, SEM, TEM, Raman, and FTIR analyses were included to\nprovide a more comprehensive understanding of the oxidation behavior.\n Synchrotron-based XAFS measurements were introduced to elucidate the Fe–O\ncoordination environment.\n The previously used color-rendered SEM images illustrating the auto-catalytic behavior\nwere replaced with corresponding EDS elemental mapping data.\n The characteristic V-shaped oxygen removal behavior of reduced iron powder was\nexplicitly explained.\n The abstract was shortened to comply with the 150-word limit.\n The “Discussion and Outlook” section was substantially revised to improve clarity and\ncontextualization.\nResponses to Reviewer 1\nComment 1：\nThe V-shaped profile in a saline environment needs to be better explained. Authors have stated\nthat “…the rate drops sharply in the first 2 hours, then gradually rises. This is likely due to two\nsynergistic effects—NaCl suppresses surface passivation, and the porous structure enhances\nreactant transport and active surface exposure.” Authors are strongly encouraged to perform\nSEM-EDX or any other surface-sensitive analysis to prove this phenomenon.\nResponse:\nThank you for highlighting the V-shaped kinetic profile in the saline environment and for\nsuggesting additional surface-sensitive characterization. We agree that this behavior warrants\na more rigorous explanation, and we have therefore substantially expanded the discussion in\nthe revised manuscript and added new experimental evidence.\nFirst, the oxidation evolution of the reduced iron powder at different reaction times was\ninvestigated by XRD, as shown in Fig. R1. The results indicate that Fe O and FeO(OH) are\n3 4\nformed simultaneously during the reaction. Importantly, these two phases play competing roles:\nFe O is relatively unfavorable for oxygen adsorption, whereas FeO(OH) is beneficial due to\n3 4\nits porous and hydroxylated nature. At the early stage (2 h), Fe O is the dominant phase,\n3 4\ncorresponding to the minimum oxygen removal rate. As the reaction proceeds, the intensity of\nFeO(OH) diffraction peaks increases markedly at 6 h and 8 h, which correlates well with the\nsubsequent recovery and increase in the reaction rate. This competitive phase evolution\nprovides a direct explanation for the observed V-shaped kinetic profile.\n◆ Fe O\n3 4\n◇ ◆\n◆◇\n◆ ◇◆ ◆ ◇ ◆\n8h\n● ● ● ● ● ● ● ●\n6h\n4h\n2h\n24 28 32 36 40 44 48 52 56 60 64\nFigure R1. XRD patterns of the reduced iron powder oxygen scavenger at different\n2\n).u.a(\nytisnetnI\n◇ γ-FeOOH α-Fe Cu K\nα\n● Peaks of diatomite\nReduced iron\n2θ (°)\nreaction times. Both the reaction-unfavorable Fe O and the reaction-favorable FeO(OH) are\n3 4\nformed simultaneously during the process, giving rise to a competitive effect between the two\nphases. At the early stage (2 h), Fe O is the dominant phase, corresponding to a relatively low\n3 4\noxygen removal rate. As the reaction proceeds, the FeO(OH) phase gradually forms and\nincreases in proportion, and its diffraction peaks become markedly enhanced after 6 h and 8 h.\nIn addition, SEM observations of the reduced iron powder after 2 h and 6 h of reaction are\npresented in Fig. R2. Compared with the 2 h sample, the specimen reacted for 6 h exhibits a\nsubstantially enlarged area of loose and porous surface regions, in good agreement with the\nXRD results. These oxidized regions are preferentially distributed along surface grooves and\ndensely undulated defect-rich sites, which are known to possess higher reactivity and facilitate\nreactant transport and active surface exposure, thereby enhancing the oxygen removal\nperformance. Owing to the fundamentally different oxidation behaviors of reduced iron powder\nand iron-based amorphous alloys, this oxidation-induced morphology is distinct from that\nobserved in Fe-based MGs.\nFigure R2. SEM images of the reduced iron powder at different magnifications after 2 h\n(a–c) and 6 h (d–f) of reaction. Compared with the sample reacted for 2 h, the surface area of\nloose oxidized regions increases markedly after 6 h, in good agreement with the XRD results.\nThese oxidized regions are preferentially distributed in surface grooves and densely undulated\nareas, which act as defect-rich sites with higher reactivity and are thus beneficial for the oxygen\nremoval performance of the reduced iron powder. Owing to the distinct oxidation behaviors of\nreduced iron powder and FeSiB MG, the resulting oxidation-induced morphology differs\nsubstantially from that of the MG system.\nR3) confirms that the surface oxidation products are iron oxides, providing direct\ncompositional evidence for the surface evolution inferred from XRD and SEM analyses.\nTaken together, the combined XRD, SEM, and SEM–EDS results provide strong and\ncomplementary evidence that the V-shaped kinetic behavior arises from the competition\nbetween Fe O formation at the early stage and the progressive development of porous,\n3 4\nFeO(OH)-rich surface layers at later stages, thereby fully addressing the concern.\nWe have discussed this issue in the main text, and the corresponding images and detailed\nanalyses are provided in Supplementary Figs. 2-4.\nFigure R3. EDS elemental mapping of the reduced iron powder after 6 h of reaction. a,\nSEM image; b-d, Fe, Si and O EDS maps, respectively. The results confirm the formation of\niron oxide products on the surface of the reduced iron powder.\nComment 2：\nThe experiments were performed on a rather short experimental frame, whereas real\napplications may require months-long scavenging activity. The authors need to perform longer-\nterm (e.g., a week) tests with FeSiB MG to ensure that the material can resist long-term\nexposure to solvents with acceptable oxygen evolution rates.\nResponse:\nThank you for your constructive comment. We agree that oxygen scavengers may\nexperience prolonged storage prior to use in real applications, and we have therefore carried\nout additional long-term exposure experiments to address this concern.\ncentrifuge tube and subsequently double-sealed in a vacuum bag to simulate industrial storage\nconditions. The samples were stored at room temperature for 30 days before being subjected\nto oxygen removal tests. This protocol corresponds to long-term exposure of the FeSiB MG\npowder to a low-oxygen electrolyte environment prior to use.\nThe experimental results are shown in Fig. R4. By comparison with the results presented\nin Fig. 1 of the main text, it is evident that the oxygen removal performance of the FeSiB MG\nremains stable after prolonged solvent exposure, with no noticeable degradation in the reaction\nkinetics. This behavior is reasonable, as under long-term sealed storage conditions with\nextremely limited oxygen availability, FeSiB MG is able to maintain surface reactivity until it\nis exposed to air during actual use.\nIt should be noted that all oxygen scavengers discussed in this work are designed for\nsingle-use applications. As the oxygen removal reaction proceeds, the amount of zero-valent\niron is gradually consumed. Consequently, long-term preservation of scavenging performance\ninherently requires storage under oxygen-deficient conditions, which is consistent with both\nindustrial practice and the storage protocol adopted in this study.\nIn the revised version, we have added a dedicated section entitled “Low-temperature\nand long-term storage performance”, where the corresponding results and analysis are\npresented.\nFigure R4. Oxygen removal curve of the FeSiB MG after 30 days of sealed storage. The inset\nshows a sealed sample.\nTheoretical oxygen removal performance was assessed only on Fe content but ignores potential\nSi contribution, even though it can enhance the glass forming ability. What is the main reason\nbehind not using Si in the calculations?\nResponse：\nThank you for this insightful comment regarding the potential contribution of Si to the\noxygen removal performance. If you are referring to the role of Si in the maximum oxygen-\nremoval capacity, this has already been considered in Fig. 2c and the corresponding analysis,\nwhere the theoretical limits determined by Fe and FeSi are indicated. If, however, you mean\nthe DFT calculations involving Si (as also mentioned by the editor and Reviewer 2), our\nresponse is as follows.\nIn our initial theoretical analysis, Si was not explicitly considered because Fe is the\ndominant reactive element in the FeSiB MG and primarily governs the oxygen scavenging\nkinetics under practical conditions.\nIn the revised paper, we have now performed a comprehensive set of additional DFT\ncalculations to explicitly evaluate the oxygen adsorption activity of Si. Specifically, four new\ncalculations about Si have been added: (i) oxygen adsorption on Si sites in amorphous FeSiB\nwithout considering electrolyte effects; (ii) oxygen adsorption on Si sites in amorphous FeSiB\nwith electrolyte effects included; (iii) oxygen adsorption on crystalline Si without electrolyte\neffects; and (iv) oxygen adsorption on crystalline Si with electrolyte effects included. The\nspecific calculation method can be found in the Supplementary Material.\nThe new results (Figs. R5 and R6) demonstrate that both amorphous Si and crystalline Si\nexhibit intrinsically strong oxygen affinity, as reflected by their low oxygen adsorption barriers.\nHowever, Si is a well-known passivation-prone element, and under ambient conditions bulk Si\nrapidly forms a stable oxide layer that inhibits further reaction with oxygen. Consequently,\nconventional Si materials do not function as effective room-temperature oxygen scavengers.\nNevertheless, in metallurgical processes, the strong oxygen affinity of Si is widely exploited\nfor the deoxidation of molten steel, highlighting its fundamental thermodynamic driving force\nfor oxygen removal.\nThese results clarify that while Fe dominates the practical oxygen removal process, Si\npossesses strong intrinsic oxygen affinity and can play a synergistic role in the FeSiB MG. This\nadditional analysis directly addresses the concern and strengthens the theoretical foundation of\nthe manuscript.\nFig. R5. Energy barriers of Si for O adsorption on Si atoms in FeSiB MG with and without\n2\nsolvation effects.\nFig. R6. Energy barriers of Si for O adsorption on Si(111) surface with and without solvation\n2\neffects. Due to the four-coordinate stability and strictly localized electronic orbitals of\ncrystalline Si, it readily captures the unpaired electrons of external oxygen atoms to form\nchemical bonds. These bonds are prone to cleavage, thus endowing crystalline Si with strong\nintrinsic oxygen-adsorbing activity.\nComment 4:\nNo elemental mapping was presented to confirm how oxides are distributed. More importantly,\na single micrograph was provided to infer the general morphology, but this may not be so\nrepresentative. Authors are expected to give a low-magnification image with elemental\nmapping and/or indicate diatomite (green) and iron oxide (red) regions\nThank you for your valuable comment. To address your concern, additional SEM-EDS\nelemental mapping was conducted at representative locations. The corresponding elemental\nmaps are shown in Fig. R7b-d, with the associated SEM images provided in Fig. R8. These\nresults are consistent with those discussed in the main text, confirming that the observed oxide\ndistribution is representative rather than specific to a single micrograph.\nIt should be noted that the particle surfaces are highly irregular, with pronounced height\nvariations both within individual particles and among different particles. Because EDS\nmapping is strongly affected by surface topography, elemental maps acquired at very low\nmagnification are susceptible to significant geometric and signal-collection artifacts and\ntherefore have limited quantitative reliability in this system.\nIn the revised manuscript, we have replaced the previously color-rendered image\nwith direct SEM-EDS elemental mapping data (Fig. 5 in the revised version), thereby\nproviding a more objective and representative visualization of the spatial distribution of\ndiatomite and iron oxide phases.\nFig. R7. Origin of the pronounced autocatalytic behavior in FeSiB MG oxygen scavenger.\na, XRD patterns of reaction products from FeSiB MG, pure iron, and reduced iron under saline\nconditions. b-d SEM and EDS mapping images of the reacted FeSiB MG, revealing a coupled\nstructure of iron oxides (red) and diatomite (cyan).\nfeatures. a, The corresponding low-magnification SEM image shown in Fig. 5b. Owing to the\ndistinctive oxidation characteristics of FeO(OH), the regions enriched with iron oxidation\nproducts can in practice be identified directly from the morphological features. The red circles\nhighlight regions exhibiting similar oxidation characteristics. b–d, SEM images of other\nreacted particles.\nComment 5:\nDespite the high performance and scalability of Fe-based MGs as oxygen scavengers,\ntranslating their laboratory-scale success into real-world industrial applications poses\nchallenges. Authors are expected to acknowledge this challenge and present a forward-looking\nstatement on how to address it\nResponse:\nThank you for this insightful comment. We agree that translating the laboratory-scale\nperformance of Fe-based MG oxygen scavengers into practical industrial applications remains\na nontrivial challenge. As discussed in the manuscript, the primary bottleneck does not lie in\nthe intrinsic material design, since Fe-based MGs are compositionally simple and can be\nfabricated using well-established rapid solidification routes, but rather in achieving cost-\neffective large-scale production.\nAt present, FeSiB MGs have already been industrialized as soft magnetic materials, with\nrelatively low raw-material costs; however, their overall price is dominated by processing costs,\n9\nparticularly those associated with melt-spinning. In contrast, the oxygen scavengers proposed\nin this work do not require strict control over magnetic properties, ribbon uniformity, or\ndimensional consistency, nor do they suffer from yield losses caused by magnetic performance\nspecifications. These differences provide clear opportunities for process simplification and cost\nreduction when the material is repurposed as an oxygen scavenger.\nLooking forward, further cost reduction and performance optimization will rely on close\ncollaboration with the industry to develop scalable, continuous, and application-oriented\nfabrication processes. In parallel, extended field testing under realistic service conditions will\nbe necessary to evaluate long-term stability, system compatibility, and overall cost–benefit\nperformance.\nIn the revised manuscript, we have added a forward-looking discussion in the\n“Discussion and outlook” section to explicitly address these challenges and the pathways\ntoward industrial implementation.\nComment 1:\nThe authors state that FeSiB MG, pure iron, and reduced iron have \"matched volumetric\nparticle sizes\" (Supplementary Fig. 1), but reduced iron exhibits a porous structure with a\nspecific surface area (0.412 m²/g) over 12 times higher than FeSiB MG (0.0340 m²/g). This\ndrastic difference in surface area—known to dominate reaction kinetics in redox processes—\ninvalidates direct comparisons of \"intrinsic reactivity.\" Why was reactivity not normalized by\nsurface area to isolate the effect of amorphous structure?\nResponse：\nThank you for this thoughtful and technically important comment. We agree that specific\nsurface area is a key parameter governing reaction kinetics in redox-driven oxygen scavenging.\nThe surface-area–normalized comparison is carried out and is presented in Fig. 2d of the\noriginal manuscript (shown as Fig. R9 in this response).\nFig. R9. Radar plot comparing FeSiB MG and reduced iron across four normalized metrics: k ,\na\nweight-based, cost-based, and surface area-based oxygen removal capacities.\nIf the oxygen removal performance in Fig. 1 (in the manuscript) were also normalized\nby surface area, the apparent advantage of the FeSiB MG would become even more pronounced,\nas the newly developed scavenger delivers substantially higher oxygen removal capacity\ndespite possessing a much lower specific surface area than reduced iron. However, the primary\npurpose of Fig. 1 was to present a direct, application-oriented comparison of the practical\noxygen scavenging performance under identical experimental conditions. In this context,\nnormalizing by surface area would artificially penalize reduced iron—which intrinsically relies\n11\non its high porosity and large surface area—and would obscure the real-world performance\ndifferences among the materials.\nTherefore, we consider it more appropriate to present the non-normalized experimental\nresults in Fig. 1 to reflect actual usage performance, while Fig. 2d provides a complementary,\nsurface-area-normalized analysis to isolate intrinsic reactivity. Taken together, these two\nrepresentations allow readers to clearly distinguish between practical scavenging efficiency\nand intrinsic material reactivity, and to appreciate the superior performance of FeSiB MG from\nboth perspectives.\nComment 2:\nThe 48-hour capacity of FeSiB MG (1.596 L/g) is claimed to \"surpass the theoretical limit of\npure iron (1.566 L/g)\". This is physically implausible unless Si participates in oxygen\nscavenging, but the authors provide no stoichiometric basis for Si oxidation (e.g., 4Fe + 3O₂\n→ 2Fe₂O₃ vs. Si + O₂ → SiO₂). XPS (Supplementary Fig. 2f) shows Si⁴+ but no quantification\nof Si-derived oxygen uptake. Without this, the \"synergistic activation of Si\" remains\nspeculative.\nResponse:\nThank you for this constructive and insightful comment. We agree that exceeding the\ntheoretical oxygen removal capacity of pure iron necessarily implies the participation of\nadditional active elements, and in the revised manuscript we have strengthened both the\ntheoretical and experimental evidence for the role of Si.\nFrom a theoretical perspective, we have added several new DFT calculations\ndemonstrating that Si possesses a strong intrinsic oxygen affinity. Although elemental Si is\nwell known as an effective deoxidizer, it does not normally function as a room-temperature\noxygen scavenger due to rapid surface passivation; for this reason, its deoxidation capability is\nprimarily exploited in metallurgical processes. The relevant computational details and\nanalysis are provided in our response to Reviewer 1, Comment 3, and are incorporated into\nthe revised manuscript.\nExperimentally, quantitative analysis of Si oxidation in the original samples was\ncomplicated due to the presence of diatomite, which introduces a significant background in Si\noxidation analysis. To eliminate this interference and directly probe the contribution of Si,\nwe designed a new set of controlled oxidation experiments in the revised study.\nSpecifically, 2 g of FeSiB powder was mixed with 30 μL of NaCl solution and allowed to\n12\nreact in air. After 1 h, an additional 30 μL of NaCl solution was added, and this procedure was\nrepeated multiple times. Samples subjected to n reaction cycles were denoted as FeSiB-Rn.\nThe use of 30 μL solution per cycle was deliberately chosen to achieve micro-wetting without\nfull immersion; complete immersion would shift the reaction to a solution-phase oxygen\nconsumption process, which is inconsistent with both the standard experimental configuration\nand practical oxygen scavenger operation. Notably, commercial oxygen scavengers are also\ndesigned to operate under micro-wetting rather than fully submerged conditions, and the\nmoisture-retaining agent in our standard experiments serves the same purpose.\nXPS spectra were collected for samples reacted 10, 20, and 30 times, and the relative\nfractions of Si-derived and Fe-derived oxides in the surface oxide layers were quantified and\ncompared with those of the native oxide film and the nominal alloy composition (Fig. R10).\nTwo key observations emerge. First, even in the native oxide layer of FeSiB MG, the fraction\nof Si oxides is significantly higher than expected from the nominal composition, indicating\npreferential oxidation of Si and confirming its strong oxygen affinity, consistent with the\nDFT results. Second, as oxidation proceeds, the ratio of Si oxides to Fe oxides increases\nmonotonically. If Si did not actively participate in oxygen scavenging, progressive oxidation\nwould lead to Fe-oxide-dominated surfaces and a decreasing relative Si signal. The opposite\ntrend observed here provides direct and quantitative evidence that Si contributes\nsubstantially to the oxygen removal process.\nTaken together, these theoretical and experimental results establish a clear stoichiometric\nand mechanistic basis for Si participation in oxygen scavenging, thereby explaining how the\nmeasured oxygen removal capacity of FeSiB MG can surpass the theoretical limit of pure iron.\nFig. R10. Relative fractions of Si and Fe oxides in FeSiB surface oxide layers before and\nafter reaction, with the nominal composition shown for comparison.\nWe further provide more direct evidence for the role of Si. Fig. R11a shows an SEM\n13\nimage of the FeSiB-R20 sample. A large number of porous structures are clearly observed on\nthe surface, with part of the oxidation products exhibiting a flake-like, partially exfoliated\nmorphology. Figs. R11b-e show the corresponding EDS elemental maps of the marked region\nin Fig. R11b. The oxide layer is strongly enriched in Fe and O, and a distinct Si signal is also\nclearly detected, directly confirming the oxidation of Si.\nQuantitative EDS analysis (Fig. R11f) yields a composition of Fe 31.77 at%, Si 2.74 at%,\nand O 65.49 at%. The atomic ratio of Si to Fe is therefore 8.62%, slightly lower than the\nnominal composition ratio of 11.54%, which allows a semi-quantitative estimation of the\nrespective contributions of Si and Fe to oxygen uptake. Assuming that Si is present as SiO ,\n2\nthe contribution of Si to oxygen removal in this oxidation product can be readily calculated to\nbe 11.49%. Considering that Si may also exist in intermediate oxidation states, the actual\ncontribution of Si can be reasonably regarded as close to, but slightly lower than, 11.49%.\nIt should be noted that diatomite was deliberately excluded from this series of experiments\nto eliminate interference in Si analysis. As a result, the quantitative contribution of Si in\ndiatomite-containing samples may differ slightly. Nevertheless, these results unambiguously\ndemonstrate the active participation of Si in the oxygen scavenging process and provide a\nreasonable estimate of its contribution.\nThe “Atomic-scale insights from DFT” section in our latest manuscript discusses the\nnew simulation results, and a new section entitled “Analysis of the contribution of Si” has\nbeen added to elaborate on the role of Si.\nFig. R11.Analysis of the role of Si.a, SEM image of the FeSiB-R20 sample surface, showing\nspontaneous delamination of the oxide layer after reaction. b–e, EDS elemental maps of the\nregion highlighted in (a), indicating pronounced Fe, Si, and O signals, with only weak B signal.\n14\nf, Corresponding EDS spectrum showing the measured composition, revealing that the oxide\nlayer is primarily composed of Fe and Si oxides.\nComment 3：\nThe oxygen adsorption energy barrier (1.29 eV for FeSiB vs. 3.39 eV for crystalline Fe) is\ncomputed using a static slab model with 2 H₂O molecules, which fails to replicate the saline/\nmoist environment of the experiments. Realistic conditions involve electrolyte (NaCl) and\ndynamic water layers, which can drastically alter surface energetics. Why were these factors\nexcluded?\nResponse:\nThank you for this valuable comment. We agree that the experimental environment\ninvolves saline and moist conditions, which can influence surface energetics.\nWe do acknowledge that electrolytes such as NaCl can affect reaction kinetics under\npractical conditions, and it is indeed necessary to investigate their influence. Directly including\nexplicit NaCl molecules in DFT simulations is computationally difficult because it drastically\nenlarges the model size and increases calculation time by orders of magnitude. Therefore, we\nmodel the electrolyte effect implicitly by the VASPsol implicit solvation model (Refs. [1,2]).\nTo include the effect of the 1 wt% NaCl solution, the bulk dielectric constant is set to 76.34\nfrom interpolation of experimental data of the NaCl solution (Ref. [3]).\nIn the revised manuscript, we added six new DFT calculations to systematically evaluate\nthe oxygen adsorption activity of Fe and Si under different conditions. Therefore, there are\ncurrently a total of 8 DFT calculations as follows:\n1. Fe in FeSiB and crystalline Fe without electrolyte (original study),\n2. Fe in FeSiB and crystalline Fe with implicit electrolyte,\n3. Si in FeSiB and crystalline Si without electrolyte,\n4. Si in FeSiB and crystalline Si with implicit electrolyte.\nThe results are summarized in Fig. R12. It can be observed that the FeSiB MG still\nshows a lower energy barrier and a higher d band center than the crystalline Fe, and\ntherefore the main conclusions of the DFT calculation remain valid. The implicit solvation\nmodel stabilizes the charge-transfer–dominated transition states on pure Fe surfaces, thereby\nlowering the oxygen adsorption barrier in both systems. In contrast, Fe sites in FeSiB are\nembedded in a more delocalized bonding environment, which weakens charge polarization and\nmakes the adsorption barrier much less sensitive to electrolyte-induced electrostatic screening.\nexperimental condition is between the fully solvated and non-solvated extremes. Therefore,\nboth the original and implicit solvation calculations provide helpful insights to the oxygen\nremoval reaction.\nOverall, all DFT results consistently indicate that FeSiB MG exhibits lower oxygen\nadsorption barriers and more favorable reaction kinetics compared with crystalline Fe.\nRelevant content can be found in the main text in the section “Atomic-scale insights from\nDFT” and in Supplementary Figures 7-13.\nFig. R12. The newly added DFT calculation results. a, Energy barriers of Fe for O\n2\nadsorption on Fe(110) and FeSiB MG surfaces with implicit solvation effects. b, Energy\nbarriers of Si for O adsorption on Si atoms in FeSiB MG with and without solvation effects.\n2\nc, Energy barriers of Si for O adsorption on Si(111) surface with and without solvation effects.\n2\nd, DOS and d band centers of the surface Fe atoms of the crystalline Fe and FeSiB MG.\n[1] Implicit solvation model for density-functional study of nanocrystal surfaces and reaction\npathways. K. Mathew, R. Sundararaman, K. Letchworth-Weaver, T. A. Arias, and R. G.\nHennig, J. Chem. Phys. 140, 084106 (2014),\n[2] Implicit self-consistent electrolyte model in plane-wave density-functional theory. K.\nMathew, V. S. C. Kolluru, S. Mula, S. N. Steinmann, and R. G. Hennig, J. Chem. Phys.\n16\n151, 234101 (2019),\n[3] Eiberweiser, Andreas, and Richard Buchner. \"Ion-pair or ion-cloud relaxation? On the\norigin of small-amplitude low-frequency relaxations of weakly associating aqueous\nelectrolytes.\" Journal of Molecular Liquids 176 (2012): 52-59.\nComment 4\nXRD identifies γ-FeO(OH) as the primary oxidation product, but Raman spectra\n(Supplementary Fig. 2e) show no distinct peaks for this phase, and TEM images of the oxide\nlayer are absent. The claim that γ-FeO(OH) \"poorly adheres to the MG matrix\" is\nunsupported—how was adhesion quantified?\nResponse：\nThank you for raising this important point regarding phase identification and oxide\nadhesion.\nFirst, we would like to clarify that γ-FeO(OH) is indeed detected in the Raman spectra\n(see Fig. R13 or Supplementary Fig. 5e). In the revised manuscript, we provide additional\nand higher-quality characterization, including updated XRD (Fig. 6c in the revised\nmanuscript), Raman, FTIR, and TEM results, all of which consistently confirm γ-FeO(OH)\nas the dominant oxidation product. In particular, the Raman spectra in Fig. R14clearly exhibit\nthe broadened characteristic bands of γ-FeO(OH), accompanied by weaker features attributable\nto α-FeO(OH). The relatively weak and broadened Raman signatures arise from the\nintrinsically poor crystallinity and nanoscale nature of the hydroxide products, which are well\nknown for FeO(OH) phases formed under mild, low-temperature oxidation conditions.\nFig. R13. (Previous Supplementary Fig. 2e) Raman spectra of diatomite and reacted\nFeSiB scavenger. The reacted scavenger sample contains crystalline diatomite, whose\n17\ncharacteristic peaks interfere with the product peaks. Note that in this experiment, 0.5g of\nFeSiB and 0.8g of diatomite were used.\nFig. R14. Raman spectra of FeSiB samples before and after reaction. The samples were\nnot subjected to heat-drying treatment.\nSecond, regarding TEM evidence, a new TEM image of the oxidized layer has been added\nin the new Supplementary Material (Supplementary Fig. 17). The result is consistent with the\nXRD and Raman results as well as with the SEM observations.\nWith respect to adhesion, we emphasize that the statement that γ-FeO(OH) “poorly\nadheres to the MG matrix” is not a speculative claim introduced in this work, nor does it rely\non indirect inference alone. Poor adhesion and easy spallation of FeO(OH)-type oxides are\nwidely recognized and well documented in corrosion science and oxidation literature. This\nbehavior originates from fundamental crystallographic and physicochemical characteristics of\nFeO(OH) rather than from any specific experimental assumption in our study.\nSpecifically, FeO(OH) is a trivalent iron oxyhydroxide with a relatively simple Fe³⁺\ncoordination environment and small ionic radius, which promotes anisotropic crystal growth.\nAs a result, FeO(OH) typically forms platelet-, needle-, or nanoporous microstructures with a\nhigh density of defects and voids. These features lead to discontinuous, mechanically weak\noxide layers that are prone to cracking and exfoliation. In addition, the molar volume expansion\nassociated with the transformation from metallic Fe to FeO(OH) is significantly larger than\nthat for Fe O , which promotes stress accumulation at the oxide–metal interface and further\n3 4\nfacilitates delamination.\nIn contrast, Fe O is a mixed-valence (Fe²⁺/Fe³⁺) oxide with an inverse spinel structure,\n3 4\ncharacterized by dense atomic packing and lower defect density. The presence of Fe²⁺ partially\n18\ncompensates oxygen vacancies during growth, enabling the formation of compact, adherent,\nand passivating oxide films. These differences between FeO(OH) and Fe O are extensively\n3 4\nreported in both classical textbooks and modern studies on iron oxidation and corrosion.\nExperimentally, the weak adhesion of γ-FeO(OH) in our system is directly evidenced by\nSEM observations after reaction and after mild ultrasonic cleaning, where oxide products are\nseen to spontaneously exfoliate from the FeSiB MG surface and form a nanoporous\nmorphology (see the new Fig. 5b, Fig. 7a, Supplementary Figure 5c, and Fig. R15). Due to\nthe loose, porous, and mechanically fragile nature of FeO(OH), quantitative adhesion\nmeasurements (e.g., pull-off force determination) are inherently difficult and not commonly\nreported even in dedicated corrosion studies.\nIn summary, the combined XRD, Raman, FTIR, TEM, and SEM results unambiguously\nidentify γ-FeO(OH) as the primary oxidation product, and both fundamental materials\nchemistry and direct morphological evidence support its poor adhesion relative to compact\noxides such as Fe O . This behavior underpins the continuous exposure of fresh reactive sites\n3 4\nand is therefore fully consistent with the observed oxidation kinetics and autocatalytic\ncharacteristics discussed in this work.\nFig. R15. Nano-porous surface structure of FeSiB-R20 sample. It is clearly seen that the\noxides are spontaneously exfoliated.\nComment 5\n5. Autocatalysis requires a product to accelerate the reaction, but the authors attribute it to\n\"nanoporous γ-FeO(OH) + diatomite\" without kinetic evidence (e.g., rate vs. product\nconcentration plots).\nResponse:\ntransformed the data in Figure 1 into reaction rate versus product mass plots, with the product\nquantified as FeO(OH), as shown in Fig. R16 (or Supplementary Figure 15).\nUnder electrolyte-free conditions, the reaction rate sharply increases after 2 h,\ndemonstrating classic autocatalytic behavior, while in saline conditions, this sharp increase\noccurs after just 1 h, also reflecting typical autocatalysis (the first half of the curve in Fig. R17).\nIt is noteworthy that, unlike conventional autocatalytic systems, where the initial reaction is\nslow due to the absence of catalyst, this system exhibits a relatively high initial rate, which is\na distinctive feature.\nDue to experimental limitations, oxygen content cannot be accurately recorded when\napproaching zero, so the later stage where the reaction rate would plateau is not captured.\nOverall, these results confirm that the observed acceleration of the reaction is consistent\nwith autocatalytic behavior, with γ-FeO(OH) and diatomite acting as structural and chemical\nfacilitators.\nFig. R16. Correlation curves between the kinetic oxygen removal rate and the mass of\nreaction products. a, Under non-saline condition; b, Under saline condition.\nFig. R17. A typical autocatalytic curve.\nThe \"1–4 orders of magnitude higher rate\" (Fig. 2e) compares FeSiB to systems like glucose\noxidase and tocopherol, which operate via entirely different mechanisms (enzymatic vs. redox).\nA fair comparison would include state-of-the-art Fe-based scavengers (e.g., nano-Fe@C\ncomposites), but these are omitted. Why?\nResponse:\nThank you for this comment. In Fig. 2e, we intentionally compiled representative oxygen-\nscavenging systems reported in the literature to provide readers with a broad, quantitative\nbenchmark across different classes of scavengers. Although these systems operate via distinct\nmechanisms (e.g., enzymatic, antioxidant, or redox-based), such cross-category comparisons\nare commonly adopted in the field to contextualize performance metrics such as reaction rate.\nIndeed, several authoritative reviews present and compare diverse oxygen scavengers within a\nsingle framework despite mechanistic differences (e.g., Ref. [4,5] below).\nWith respect to state-of-the-art Fe-based scavengers, these materials are not omitted.\nIn\nFig. 2e, the system labeled as “nano-Fe” corresponds to nanosized Fe@C composite\nscavengers reported in the literature. Specifically, this data point is taken from Mu et al. (Food\nChemistry, 2013), where the scavenger is explicitly described as a composite consisting of Fe\nnanoparticles, activated carbon, NaCl, and CaCl (mixed at a 1:1:1:0.2 weight ratio) prepared\n2\nunder an N atmosphere (Ref. [6]).\nscavengers, and the observed 1–4 orders of magnitude higher oxygen removal rate achieved by\nFeSiB MG remains a valid and meaningful performance benchmark.\n[4] Cichello S A. Oxygen absorbers in food preservation: a review[J]. Journal of food science\nand technology, 2015, 52(4): 1889-1895.\n[5] Dey A, Neogi S. Oxygen scavengers for food packaging applications: A review[J]. Trends\nin\nTrends in Food Science & Technology, 2019, 90: 26-34.\n[6] Mu H, Gao H, Chen H, et al. A nanosised oxygen scavenger: Preparation and antioxidant\napplication to roasted sunflower seeds and walnuts[J]. Food Chemistry, 2013, 136(1): 245-\n250.\nComment 7:\nError bars in Figs. 1b,c are small (±0.02%), but the authors report \"n=3\" without details on\n21\nreproducibility. Given the high variability in powder-based reactions, were replicate\nexperiments conducted with different batches of materials?\nResponse:\nThank you for your comment. It appears there is a misunderstanding regarding the error\nbars in Figures 1b and 1c. The percentages indicated correspond to concentration values, not\nabsolute errors, and the actual variability in the measurements is approximately 2–5%, not\n±0.02%.\nTable 1 presents the detailed data for three experiments under non-saline conditions, while\nTable 2 summarizes the average concentration changes and associated errors for 3 materials\nunder non-saline conditions. These data demonstrate that the observed variability is within the\nstated 2–5% range. Additional experimental results and raw data are provided in the submitted\ndata package.\nThe core experimental material, FeSiB amorphous powder, is a mass-produced industrial\nproduct with a standardized and stable composition. This ensures high consistency and stability\nacross different batches of our materials. Furthermore, our reaction system is straightforward,\nyielding excellent reproducibility with a low technical barrier to entry. We fully welcome and\nencourage other research groups to replicate our findings.\nTable 1. Detailed data for three experiments under electrolyte-free conditions\nTime(h)(1st) O2 (%) Time(h)(2nd) O2 (%) Time(h)(3rd) O2 (%)\n0 20.9 0 20.9 0 20.9\n0.16667 19 0.16667 18.7 0.16667 18.8\n0.5 17.1 0.5 16.8 0.5 17\n1 15.5 1 14.9 1 15.2\n2 13.3 2 12.6 2 12.8\n3 11.6 3 10.7 3 11\n4 9.9 4 9.1 4 9.5\n5 8.4 5 7.5 5 8\n6 6.9 6 6.1 6 6.7\n7 5.5 7 4.7 7 5.4\n8 4.2 8 3.4 8 4.2\n9 3 9 2.2 9 3.1\n10 1.9 10 1.1 10 2.1\n11 0.9 11 0.2 11 1.2\n12 0.1 11.25 0 12 0.3\n12.16667 0 -- -- 12.41667 0\nunder non-saline conditions.\nFeSiB MG Pure ion Reduced iron\nTime(h) O2 (%) Error Time(h) O2 (%) Error Time(h) O2 (%) Error\n0 20.9 0 0 20.9 0 0 20.9 0\n0.16667 18.83333 0.15275 1 20.06667 0.05774 1 19.2 0.52915\n0.5 16.96667 0.15275 2 19.7 0.1 2 18.6 0.60828\n1 15.2 0.3 3 19.46667 0.11547 3 18.16667 0.57735\n2 12.9 0.36056 4 19.2 0.17321 4 17.83333 0.55076\n3 11.1 0.45826 5 19.06667 0.20817 5 17.6 0.60828\n4 9.5 0.4 6 18.9 0.2 6 17.4 0.60828\n5 7.96667 0.45092 7 18.73333 0.25166 7 17.23333 0.55076\n6 6.56667 0.41633 8 18.63333 0.25166 8 17.1 0.60828\n7 5.2 0.43589 9 18.5 0.3 9 16.96667 0.66583\n8 3.93333 0.46188 10 18.4 0.3 10 16.86667 0.57735\n9 2.76667 0.49329 11 18.3 0.4 11 16.8 0.60828\n10 1.7 0.52915 12 18.23333 0.40415 12 16.73333 0.63509\n11 0.76667 0.51316 13 18.13333 0.40415 13 16.66667 0.57735\n12 0.13333 0.15275 14 18.06667 0.45092 14 16.63333 0.63509\n-- -- -- 15 18 0.45826 15 16.56667 0.57735\n16 17.93333 0.50332 16 16.56667 0.57735\n17 17.83333 0.50332 17 16.5 0.60828\n18 17.83333 0.50332 18 16.46667 0.57735\n19 17.8 0.55678 19 16.46667 0.57735\n20 17.73333 0.56862 20 16.4 0.60828\n21 17.66667 0.61101 21 16.36667 0.57735\n22 17.66667 0.61101 22 16.36667 0.57735\n23 17.63333 0.66583 23 16.36667 0.57735\n24 17.56667 0.61101 24 16.33333 0.63509\nComment 8:\nThe DFT calculations (page 9) simulate O₂ adsorption on static surfaces with 2 H₂O molecules,\nignoring the role of NaCl electrolyte (critical for enhancing kinetics, Fig. 1c). How do Cl⁻ ions\naffect O₂ adsorption energy barriers or Fe d-band centers? Would a more realistic electrolyte-\ninclusive model alter the proposed atomic-scale mechanism?\nResponse:\nThank you for this valuable comment. We agree that the saline and moist conditions,\nincluding the Cl⁻ ions, can influence the adsorption process. We have conducted the additional\nDFT calculation to include these effects, as shown in the response to your Comment 3.\nbarriers and more favorable reaction kinetics compared with crystalline Fe.\nComment 9：\nThe manuscript focuses on short-term performance (≤48 hours), but practical applications\nrequire long-term stability. Does FeSiB MG undergo passivation over extended use (e.g., 1\nweek), and if so, what is the mechanism (e.g., crystalline oxide layer formation)? Can the\nscavenger be regenerated (e.g., via reduction) without losing activity?\nResponse:\nWe appreciate your insightful comment regarding the long-term stability and practical\napplication of our material. We have addressed these concerns as follows:\nRegarding passivation and extended use: Our experimental results indicate that FeSiB\nMG does not undergo passivation during the oxygen-scavenging process. In fact, our capacity\ntests demonstrate that the material remains active until it is nearly fully oxidized (see Fig. 2c\nin the manuscript), maintaining high reaction rates without the formation of a limiting oxide\nlayer.\nLong-term storage stability: For practical applications, we agree that long-term stability\nis crucial. We interpret this primarily as the “shelf-life” of the scavenger under anaerobic\nconditions. To address this, we have conducted additional experiments: FeSiB powders were\nsealed in 10 mL centrifuge tubes for 30 days. Subsequent testing showed no significant decline\nin their oxygen removal performance, confirming their excellent storage stability. (Please also\nrefer to our Response to Reviewer 1, Comment 2 for details). The relevant results and\ndiscussion are detailed in the original text under the section “Low-temperature and long-\nterm storage performance”.\nRegeneration: Consistent with current commercially available Fe-based oxygen\nscavengers, our material is designed for single-use. While regeneration via reduction is\ntheoretically possible, the energy consumption and associated costs would far exceed the value\nof the raw material itself, making it economically unfeasible for industrial use.\nComment 10:\nWhile FeSiB, FePC, and FeSiBC are tested (Supplementary Fig. 9), the correlation between\nMG composition (e.g., B/Si/C content) and oxygen-scavenging performance is unexplored.\nFor instance: Does increasing Si content systematically enhance capacity, or is there a critical\n24\nthreshold? How do alloying elements (e.g., Nb, Cu in FeSiBNbCu) influence oxidation kinetics?\nResponse:\nWe thank the reviewer for this insightful comment. We fully agree that alloy\ncomposition—such as B/Si/C contents—and multicomponent alloying (e.g., Nb and Cu in\nFeSiBNbCu alloys) can play an important role in oxidation and oxygen-scavenging behavior,\nand that this topic deserves systematic investigation. However, two practical scientific\nconstraints limit a comprehensive discussion within the scope of the present work.\nFirst, the glass-forming ability (GFA) imposes a strong compositional constraint. In\nFe-based MGs, elements such as Si and B simultaneously govern both chemical reactivity and\nGFA. Deviating either above or below an optimal Si (or B) content can readily induce partial\nor full crystallization, as illustrated in Fig. R18 below. As a result, systematically varying Si\ncontent while strictly maintaining a fully amorphous structure—and thereby establishing a\nclear “threshold” relationship between composition and oxygen-scavenging performance—is\nexperimentally challenging.\nFig. R18. Effect of Si content on the glass-forming ability of Fe-Si-B MGs.\nSecond, in higher-order systems such as FeSiBNbCu, the underlying mechanisms\nbecome substantially more complex. Coupled effects among multiple alloying elements can\nsimultaneously influence oxidation kinetics, passive film structure, and local chemical\nenvironments. Disentangling the individual contributions of Nb, Cu, or other elements would\nrequire extensive, dedicated studies that go well beyond the scope of the present manuscript.\nDespite these limitations, we fully acknowledge the scientific importance of these\nquestions and intend to address them in future work. The primary objective of the current study\nis to elucidate the fundamental oxygen-scavenging behavior and unique mechanistic features\n25\nof a representative FeSiB MG system. Accordingly, a broader, composition–performance\nmapping was not pursued here. We sincerely appreciate the reviewer’s constructive suggestion,\nwhich will help guide our future research directions.\nComment 11:\nThe experiments are conducted at 298 K, but real-world applications involve variable\ntemperatures/humidity. How does performance degrade at extreme conditions (e.g., <273 K\nor >333 K, low relative humidity)? Does the amorphous structure remain stable under these\nconditions, or does devitrification occur, altering reactivity?\nResponse:\nThank you for this professional and important suggestion. The effects of humidity and\ntemperature on performance are addressed as follows.\nThe Fe-based MG oxygen scavenger developed in this study is a water-rich composite\nsystem. In the standard experimental configuration, it consists of 2 g of FeSiB powder, 0.8 g\nof diatomite, and 1 g of water. The water content in the system is excessive for oxygen-\nscavenging reactions. Therefore, fluctuations in ambient humidity have a negligible\neffect on its oxygen-scavenging performance. The performance of a few commercial\noxygen scavengers is somewhat influenced by humidity; however, their systems are\nfundamentally different from ours and are beyond the scope of this study.\nIn practical applications, Fe-based oxygen scavengers are typically used within a\ntemperature range of 15–30 °C (288–303 K). For conventional Fe powder-based scavengers,\nlow temperature severely suppresses reaction kinetics, and their oxygen-removal capability\nbecomes weak below 10 °C (283 K).\nRegarding high-temperature conditions, we attempted experiments at 55 °C (328 K).\nHowever, at this temperature the water-retaining agent (diatomite) was unable to effectively\nretain water, leading to rapid evaporation. This not only disrupted the core reaction\nenvironment required for oxygen scavenging but also caused damage to the oxygen sensor,\npreventing reliable high-temperature measurements.\nTo evaluate low-temperature adaptability, we conducted comparative experiments at 5 °C\n(278 K). As shown in Fig. R19, the oxygen-scavenging efficiency of conventional reduced\niron powder decreases dramatically under these conditions, removing only ~50% of the oxygen\nwithin 24 h, which is insufficient for applications such as food and pharmaceutical preservation.\nIn contrast, the Fe-based MG scavenger maintains a high oxygen-removal rate and is able to\nfully consume oxygen in sealed containers within a much shorter time, thereby overcoming\n26\nthe low-temperature limitation of traditional scavengers.\nWe also explored an extreme low-temperature condition of -10 °C (263 K, below the\nfreezing point). Due to the water-containing nature of the system, the composite rapidly freezes\nat this temperature, and the oxygen-scavenging reaction effectively ceases (Fig. R20). This\nindicates that such water-assisted scavengers are not suitable for sub-freezing environments.\nOverall, these results demonstrate that Fe-based MG scavengers exhibit significantly\nsuperior oxygen-removal performance compared with conventional materials under room\ntemperature and non-freezing low-temperature conditions.\nIn the revised manuscript, we added a dedicated section entitled “Low-temperature and\nlong-term storage performance” to specifically discuss the low-temperature performance of\nthe FeSiB oxygen scavenger.\nFig. R19. Oxygen-scavenging curves of FeSiB MG and reduced iron powder at 278 K.\nThe samples were prepared at 298 K and subsequently transferred to a constant-temperature\nchamber at 278 K for testing. Reduced iron releases physically adsorbed oxygen upon cooling,\ncausing a fluctuation in the blue curve between 1 and 2 h.\nat room temperature and then transferred to a temperature-controlled freezer for testing. After\nthe moisture in the system froze, both materials almost lost their oxygen-scavenging capability.\nComment 12:\nThe cost analysis (Supplementary Fig. 3) compares raw material prices but ignores processing\ncosts (e.g., gas atomization for FeSiB-2). How does scalability (e.g., ton-scale production)\naffect cost, and can Fe-based MGs compete with established low-cost scavengers (e.g., reduced\niron) in high-volume applications (e.g., food packaging)?\nResponse：\nThank you for this important comment. We agree that processing cost and scalability are\ncritical factors for real-world implementation, and we clarify these points below.\nFirst, we would like to clarify that the previous Supplementary Fig. 3 and the associated\ncost analysis are based specifically on the low-cost, flake-type FeSiB MG, rather than on\nother Fe-based MG compositions or high-cost processing routes. Importantly, the estimated\ncost already includes the major processing expenses. The cost breakdown is as follows: the raw\nmaterial cost is approximately 3,800 CNY per ton, while the core processing and auxiliary\ncosts are estimated at 4,000–4,700 CNY per ton. This results in a total estimated large-scale\ncost of ~7,800–8,500 CNY per ton (7.8–8.5 CNY per kg). These values were discussed with\nindustrial partners and are representative of current conditions in China; all prices quoted refer\nto the Chinese market.\nRegarding scalability (ton-scale and above), it is necessary to distinguish between\ndifferent application requirements. In China, soft-magnetic FeSiB MG ribbons are already\nproduced at a very large scale (annual production exceeding 100,000 tons). Such materials\nmust meet stringent requirements for magnetic properties and compositional uniformity, which\nnecessitate high raw-material purity, strict process control, and inevitably generate scrap,\nresulting in a current market price of ~13,000 CNY per ton (with actual production cost being\nlower). In contrast, Fe-based MGs used as oxygen scavengers do not require magnetic\nperformance, dimensional uniformity, or ribbon integrity. Their sole functional requirement is\noxygen-scavenging activity. Consequently, raw-material pretreatment and process control can\nbe significantly simplified, and the scrap rate can be reduced to a very low level, leading to\nsubstantially lower overall production costs at scale.\nWith respect to competitiveness in high-volume applications such as food packaging, Fe-\n28\nbased MG scavengers can offset their higher unit price through superior kinetics and efficiency.\nSpecifically, complete oxygen removal by FeSiB MG can be achieved in less than one quarter\nof the time required for reduced iron powder, enabling rapid establishment of an oxygen-free\nenvironment and improved preservation performance, particularly for oxygen-sensitive foods\nand pharmaceuticals. Moreover, the 12 h and 24 h oxygen-removal capacities of FeSiB are\napproximately 2–3 times higher than those of reduced iron powder, meaning that only one-\nthird to one-half of the material mass is required to achieve the same preservation effect.\nEven when comparing the upper-bound cost of FeSiB (~8.5 CNY per kg) with the lower-\nbound cost of reduced iron powder used in scavengers (~6 CNY per kg), the cost per unit\noxygen removed is estimated to be ~2.8–4.2 CNY for FeSiB, versus ~6 CNY for reduced iron.\nTherefore,when evaluated on a performance-normalized basis, Fe-based MG scavengers\nretain a clear cost advantage and are well positioned to compete in large-scale, cost-sensitive\napplications such as food packaging. We have discussed this issue in the “Discussion and\noutlook” section of the revised manuscript.\nComment 13:\nThe manuscript suggests applications in \"gas purification\" and \"semiconductor manufacturing\"\n(p. 22) but provides no data on compatibility with these systems. For example: Does the\nscavenger release toxic byproducts (e.g., B oxides) that could contaminate semiconductor\nenvironments? How does it perform in gas streams with impurities (e.g., CO₂, H₂S)\ncommon in industrial settings?\nResponse：\nThank you for this valuable comment. We agree that compatibility with gas purification\nand semiconductor manufacturing systems requires careful consideration. We would like to\nclarify that the discussion of “gas purification” and “semiconductor manufacturing” appears\nonly in the Outlook section of the manuscript, and is intended to indicate potential application\nscenarios from a mechanistic perspective, rather than to imply that the material has already\npassed the stringent compatibility validations required for these fields. To avoid\nmisunderstanding, we clarify the relevant points as follows.\nByproducts and potential contamination risks. The FeSiB oxygen scavenger\ninvestigated in this work reacts predominantly to form solid-state oxidation products during\noxygen removal. No volatile species are generated at room temperature during the reaction.\nTherefore, under conditions with relatively moderate cleanliness requirements—such as certain\n29\npackaging processes, circuit board soldering, or general inert-gas protection environments—\nthe solid reaction products are unlikely to cause significant contamination or cross-interference.\nNevertheless, for semiconductor critical processes that demand ultrahigh cleanliness,\nsystematic evaluations of particulate release, surface residues, and long-term environmental\ncompatibility of these solid products would still be required. Such assessments are beyond the\nscope of the present study.\nPerformance in gas streams containing impurities (e.g., CO , H S). The experimental\n2 2\nsystem in this work focuses exclusively on oxygen removal from air, and does not address the\ninfluence of other industrial gas impurities. In gas streams containing sulfur species or acidic\ncomponents (such as CO or H S), the corrosion chemistry and oxidation kinetics of the\n2 2\nmaterial may be altered, potentially affecting both performance and durability. These effects\nwould require independent mechanistic studies and long-term stability tests, which constitute\nimportant directions for future work but fall outside the scope of the present manuscript.\nIn the “Discussion and outlook” section of the revised manuscript, we have further\nemphasized that the aforementioned applications are potential directions that require\ndedicated experimental validation in future studies, and should not be interpreted as established\nconclusions of this work. We sincerely thank the reviewer for this constructive comment, which\nhas helped us to clarify the scope and limitations of the study more clearly.\nComment 14:\nSome suggestions are provided:\n1) To validate the Role of Amorphous Structure in Oxygen Adsorption, In-situ X-ray\nAbsorption Fine Structure (XAFS) should be conducted. comparing Fe’s coordination in\namorphous vs. crystalline Fe before/after reaction would reveal whether the amorphous\nstructure promotes more labile Fe-O bonding, supporting DFT claims of lower adsorption\nbarriers.\n2) Quantifying Si’s Synergistic Oxidation, in-situ Raman Spectroscopy with Isotopic\nLabeling should be useful. Using 18O2 instead of ambient 16O2 during reactions, combined with\nin-situ Raman, can distinguish O incorporation into Fe oxides vs. Si oxides (via shifted\nvibrational modes of 18O2-containing species).\n3) To verify Long-Term Stability and Practical Viability, the authors can conduct Operando\nXRD under Humid/Saline Conditions. Existing XRD characterizes post-reaction products, but\noperando XRD would track oxide phase evolution (e.g., γ-FeO(OH) vs. passivating Fe₃O₄) in\nreal time under moist/saline conditions.\n30\n4) To probe the Autocatalysis and Oxide Adhesion, In-situ Atomic Force Microscopy (AFM)\nwith Nanomechanical Mapping can be performed. Measuring the force required to detach\noxide nanoparticles from the MG surface (vs. crystalline Fe) would experimentally validate claims\nthat γ-FeO(OH) “poorly adheres” to the MG matrix, sustaining active sites.\nResponse:\nThank you very much for your insightful suggestions, the following are the answers to\nthese questions.\n1) The role of amorphous structure in oxygen adsorption (XAFS)\nDue to the relatively high water content in the material, the available facilities were unable\nto perform XAFS measurements on the as-prepared samples. Therefore, to quantitatively\ncompare the oxidation degree and Fe–O coordination environments of FeSiB MG and pure\niron, synchrotron X-ray absorption measurements were conducted on samples reacted for 5.5\nh and subsequently dried. The results are shown in Fig. R21.\nFig. R21a presents the Fe K-edge XANES spectra of FeSiB before reaction, FeSiB after\nreaction, and pure iron after reaction. The absorption edge position reflects the average\noxidation state of Fe. Compared with the absorption edge of reacted FeSiB, the absorption edge\nof reacted pure iron exhibits a pronounced shift toward lower energy, indicating a lower\naverage Fe oxidation state. In addition, the spectral intensity differences highlighted by the red\narrows further confirm that FeSiB MG undergoes a higher degree of oxidation.\nThe corresponding EXAFS spectra in R space without phase-shift correction are shown in\nFig. R21b, which provide insight into the local Fe–O coordination structure. Compared with\nthe pristine alloy, the reacted FeSiB sample shows no residual metallic Fe coordination signal.\nIts first-shell Fe–O peak is broadened (R ≈ 1.3–1.5 Å), accompanied by weak but continuous\nsecond-shell features (R ≈ 2.6–2.9 Å), while contributions from higher coordination shells are\nsignificantly attenuated. This coordination fingerprint is characteristic of low-crystallinity iron\noxyhydroxides, resembling γ-FeO(OH).\nIn contrast, the reacted pure iron sample exhibits distinctly different EXAFS features. A\nstrong first-shell Fe–O peak appears at 1.1–1.5 Å, together with a pronounced second-shell\ncontribution at 2.6–2.9 Å and moderately intense signals retained in the 3.5–4.5 Å range,\nindicative of a mixed coordination environment dominated by Fe O and accompanied by\n3 4\nFeO(OH). A weak feature at approximately 2.3 Å can be assigned to a small amount of residual\nmetallic Fe.\nTaken together, the XANES and EXAFS results clearly demonstrate that Fe in FeSiB\niron, which is fully consistent with its superior oxygen-scavenging performance. Related\ndiscussions have been incorporated into the main text in the section titled “Analysis of\noxidation behavior”.\nFig. R21. XAFS results. a, Fe K-edge XANES spectra of FeSiB before and after reaction, and\nof pure Fe after reaction. b, R-space EXAFS spectra (phase shift not corrected) of FeSiB before\nand after reaction, and of pure Fe after reaction.\n2)Si’s synergistic oxidation effect\nWe appreciate the suggestion regarding the use of in-situ Raman spectroscopy combined\nwith isotopic labeling (18O₂) to elucidate the synergistic oxidation role of Si. However, the\npractical implementation in our system faces substantial experimental limitations, as clarified\nbelow.\nFirst, the oxygen scavenger used in this study contains a large fraction of diatomite,\nwhose lattice structure is strongly influenced by grain size and intrinsic impurities. As a\nresult, its diffraction and vibrational features are inherently broadened and slightly shifted\nrelative to those of pristine crystalline SiO . When diatomite coats the surface of FeSiB\n2\npowders, it introduces a strong and spatially heterogeneous Raman background, which severely\ninterferes with the reliable identification of Si-related vibrational modes.\nMoreover, the Si oxide species generated during the oxidation of FeSiB MG exhibit\nvery poor crystallinity. Their Raman bands are therefore significantly broadened, and\nsubstituting 16O₂ with 18O₂ does not produce sufficiently distinguishable spectral shifts to\nreliably differentiate between the two types of silica-related species. In addition, due to the\nintrinsic atomic interactions among Fe, Si, and B, FeSiB itself exhibits broad baseline Raman\nfeatures, further complicating spectral deconvolution. Consequently, even isotopic labeling\n32\nexperiments would not allow unambiguous discrimination of Si oxidation pathways in this\nsystem.\nIn the experiments where diatomite was removed, we first attempted to evaluate the\nformation of reaction products using Raman spectroscopy, and the results are shown inFig.\nR22. By comparing the Raman spectra of the FeSiB samples before and after reaction, distinct\ncharacteristic peaks of γ-FeO(OH) can be clearly observed, accompanied by weaker signals\nattributable to α-FeO(OH), whereas features associated with SiO are not prominent. This is\n2\nmainly due to the low Si content in the alloy and the poor crystallinity of the Si oxide species\nformed during oxidation.\nFig. R22. Raman spectra of FeSiB samples before and after reaction. The samples were\nnot subjected to heat-drying treatment.\nWe also employed infrared (IR) spectroscopy to assess the reaction products, and the\ncorresponding results are presented in Fig. R23. Owing to the presence of numerous intrinsic\nabsorption bands in FeSiB, severe spectral overlap and signal interference are unavoidable.\nNevertheless, the broadened characteristic absorption band of γ-FeO(OH) and a relatively weak\nband corresponding to α-FeO(OH) can still be clearly identified. In contrast, the spectral\nfeatures of SiO remain indistinct because of its low content and poor crystallinity.\ntechniques are inherently unsuitable for quantitative analysis. The FeSiB alloy contains a\nlarge number of Fe–Si and Fe–B bonds, which give rise to numerous overlapping vibrational\nmodes that obscure Si–O–related features. In addition, the low concentration and poor\ncrystallinity of the oxidation products lead to significant peak broadening, further reducing\n33\nspectral resolution. As a result, spectral signatures associated with Si oxidation cannot be\nreliably isolated or quantified.\nDespite these limitations, both Raman and IR spectroscopy consistently indicate the\nformation of γ-FeO(OH) and α-FeO(OH), with γ-FeO(OH) being the dominant phase, in\ngood agreement with the XRD results. Moreover, we have designed a simple yet effective\nexperiment that directly demonstrates the role of Si, as discussed in detail in our response\nto Comment 2 and in the main text section entitled “Analysis of the contribution of Si”.\nFig. R23. Infrared spectra of FeSiB samples before and after reaction. Prior to\nmeasurement, the samples were dried at 393 K.\n3) Long-term stability and practical applicability\nWe appreciate your constructive suggestion regarding operando XRD to probe real-time\nphase evolution under humid or saline conditions. Long-term stability and practical viability\nare indeed critical for oxygen-scavenging materials, and we have addressed these aspects\nthrough both durability testing and complementary structural characterization.\nFirst, to directly evaluate long-term stability under realistic storage conditions, we\ndesigned a 30-day sealed storage experiment, which effectively demonstrates the sustained\noxygen-scavenging capability of the FeSiB-based scavenger over extended periods. The\ndetailed results and discussion are provided in our response to Reviewer 1, Comment 2, and\nare now included in the manuscript in the section entitled “Low-temperature and long-term\nstorage performance.” These results confirm that the material maintains reactivity without\npassivation during prolonged storage.\nWe also attempted operando XRD measurements to monitor phase evolution during the\nreaction. As shown in Fig. R24, the diffraction patterns are severely affected by the presence\nof diatomite. The low crystallinity of the product also affects the judgment of diffraction peaks.\nIn addition, the substantial water content in the composite scavenger can lead to strong X-ray\nabsorption. As a result, the operando XRD data do not provide reliable or interpretable\ninformation on oxide phase evolution.\nEven when diatomite was replaced with glass powder to suppress crystalline interference\n(Fig. R25), the combined effects of water and the low content of reaction products under\noperando conditions still prevented clear identification of newly formed oxide phases.\nTherefore, under the present experimental configuration, we find that the operando XRD is not\na suitable tool for tracking phase evolution in this highly hydrated system.\nTo overcome these limitations, we designed an alternative reaction protocol that eliminates\ndiatomite interference and enables time-resolved characterization of oxidation products.\nSamples collected at different reaction times were analyzed by Raman and infrared\nspectroscopy, and the corresponding results are shown in Figs. R22 and R23. These data\nclearly reveal the evolution of γ-FeO(OH) as the dominant product, together with α-FeO(OH)\nas a minor phase, providing indirect but reliable insight into the oxidation pathway and the\nabsence of rapid passivation by Fe O . The associated analysis is discussed in the final\n3 4\nparagraph of the section “Analysis of the contribution of Si” .\nOverall, while we agree that operando XRD would be highly valuable in principle,\npractical limitations associated with water-rich composite systems currently prevent its\neffective implementation. We therefore rely on long-term storage tests combined with\ncomplementary spectroscopic analyses to substantiate the stability and practical viability of the\nproposed oxygen scavenger.\nFig. R24. In-situ XRD patterns of FeSiB scavenger. The numbers in the figure represent the\n35\ntest rounds. Each round of testing lasts approximately 10 minutes. It can be seen that the\ndiffraction peaks of a large amount of diatomaceous earth interfere with the product peaks.\nFig. R25. The XRD test results of the FeSiB scavenger after replacing diatomite with glass\npowder. The specific material formula has been adjusted. Under this condition, it is also\ndifficult to judge the formation of the product.\n4) About probing autocatalysis and oxide adhesion by AFM\nThank you for your suggestion to use AFM to quantify oxide adhesion. In principle, such\nmeasurements would indeed provide valuable information on oxide–substrate interactions.\nHowever, in the present system, this approach is not experimentally feasible.\nThe surface of the FeSiB-based oxygen scavenger after reaction is highly rough and\nhierarchically structured, with pronounced height variations arising from heterogeneous\noxidation, nanoporous product formation, and partial delamination of oxide species. Under\nthese conditions, AFM imaging and force–distance measurements cannot be performed in a\nreliable or reproducible manner, as stable tip–sample contact and well-defined detachment\nevents are not achievable.\nInstead, we provide direct experimental evidence for the weak adhesion and facile\ndetachment of γ-FeO(OH) from the MG matrix using complementary and more suitable\nmethods. Specifically, ultrasonic cleaning combined with post-treatment SEM observations\ndemonstrates that the oxidation products are readily removed from the FeSiB surface. As\nshown in Fig. R26, the FeSiB-R20 sample exhibits a clearly developed nanoporous\nmorphology, and the oxide products are observed to spontaneously exfoliate from the substrate\nrather than forming a dense, adherent passivation layer. This behavior is in sharp contrast to\ncrystalline Fe, where compact oxides typically remain attached and progressively block active\nsites.\nIt is also worth emphasizing that the poor adhesion of trivalent iron oxyhydroxides such\nas γ-FeO(OH) on metallic substrates is a well-established phenomenon, widely documented in\nthe corrosion and oxidation literature and even discussed in standard textbooks. This\ncharacteristic is therefore not a speculative assumption introduced in this work, but rather a\nknown materials property that our experimental observations directly corroborate in the context\nof FeSiB MG.\nTaken together, although AFM-based nanomechanical measurements are not applicable to\nthis rough, water-rich, and dynamically evolving surface, the combination of morphological\nevolution, ultrasonic detachment behavior, and established literature consensus provides robust\nexperimental support for our conclusion that weakly adhering γ-FeO(OH) continuously\nexposes fresh active sites, thereby sustaining the observed autocatalytic oxygen-scavenging\nbehavior.\nAt last, we would like to clarify that the present work is fundamentally focused on\nthe kinetic and thermodynamic behavior of a new class of Fe-based MG oxygen\nscavengers, rather than on application-specific service performance. The study addresses a\ncore scientific problem motivated by practical demands, combining mechanistic analysis with\nquantitative performance evaluation. Importantly, the strong application relevance of this\nmaterial should be viewed as an asset that underscores the significance and timeliness of the\nfundamental insights reported here, rather than as a limitation. We therefore believe that both\nthe scope and depth of this work are well aligned with the aims and readership of Nature\nCommunications.\nWe sincerely appreciate the reviewers’ hard work and valuable feedback on our manuscript.\nWe have carefully addressed all five points raised and revised the manuscript accordingly. The\nrevisions are highlighted with yellow background. Below is our point-by-point response:\nComment 1\nThe sentence “Poor adhesion and easy spallation of FeO(OH)-type oxides are widely\nrecognized and well documented in corrosion science and oxidation literature” (from Reviewer\n2, Comment 4) should be included in the revised text and properly cited.\nResponse:\nThank you for this suggestion. We have incorporated this sentence into the section “Origin of\nrobust autocatalytic effect” in the revised manuscript, with appropriate citations added.\nComment 2\nThere is no explicit note that the error bars correspond to concentration values and that the real\nvariability is 2–5%. This could cause confusion about reproducibility.\nResponse:\nWe have added a clear statement in the caption of Figure 1 to clarify that the error bars\nrepresent concentration values and the associated variability is in the range of 2–5%.\nComment 3\nA clarification note that this estimate (~11.5) is from controlled experiments without diatomite\nis missing.\nResponse:\nWe have revised the relevant section to explicitly state that the estimate of ~11.5 was obtained\nfrom controlled experiments in the absence of diatomite. This clarification can be found in the\nfirst paragraph of the section “Analysis of the contribution of Si”.\nComment 4\nA brief acknowledgment that Cl⁻ ion-specific effects were not explicitly modeled is needed.\nResponse:\nWe have added a brief acknowledgment in the second paragraph of the section “Atomic-scale\ninsights from DFT”, explicitly noting that Cl⁻ ion-specific effects were not included in our\nDFT modeling.\nComment 5\nAn explanation why there are practical limitations of operando XRD characterization in this\nsystem is required.\nResponse:\nWe have added an explanation of the practical limitations of operando XRD characterization\nfor this system in the first paragraph of the section “Origin of robust autocatalytic effect”."}, {"round": 2, "reviewer_comments": {"reviewer_1": "I am generally satisfied with the authors' thorough and thoughtful responses to my comments. The major concerns have\nbeen substantively addressed through additional experiments, expanded analyses, and clarifications throughout the\nmanuscript. The revisions have significantly strengthened the work, and I believe the manuscript is now much improved and\nsuitable for publication. However, I would still appreciate a few minor clarifications and refinements in several sections, as\npreviously noted, to further enhance precision and readability. Nevertheless, I consider the manuscript ready for acceptance\nin this current form.\n1) \"Poor adhesion and easy spallation of FeO(OH)-type oxides are widely recognized and well documented in corrosion\nscience and oxidation literature.\" in the Comment 4 of the Reviewer 2 should be placed in the revised text and cited.\n2) There is no explicit note that the error bars correspond to concentration values and that the real variability is 2–5%. This\ncould cause confusion about reproducibility.\n3) A clarification note that this estimate (~11.5) is from controlled experiments without diatomite is missing.\n4) A brief acknowledgment that Cl⁻ ion-specific effects were not explicitly modeled is needed.\n5) An explanation why there are practical limitations of operando XRD characterization in this system is required."}, "author_response": "Response to Reviewers\nWe sincerely appreciate the reviewers’ hard work and valuable feedback on our manuscript.\nWe have carefully addressed all five points raised and revised the manuscript accordingly. The\nrevisions are highlighted with yellow background. Below is our point-by-point response:\nComment 1\nThe sentence “Poor adhesion and easy spallation of FeO(OH)-type oxides are widely\nrecognized and well documented in corrosion science and oxidation literature” (from Reviewer\n2, Comment 4) should be included in the revised text and properly cited.\nResponse:\nThank you for this suggestion. We have incorporated this sentence into the section “Origin of\nrobust autocatalytic effect” in the revised manuscript, with appropriate citations added.\nComment 2\nThere is no explicit note that the error bars correspond to concentration values and that the real\nvariability is 2–5%. This could cause confusion about reproducibility.\nResponse:\nWe have added a clear statement in the caption of Figure 1 to clarify that the error bars\nrepresent concentration values and the associated variability is in the range of 2–5%.\nComment 3\nA clarification note that this estimate (~11.5) is from controlled experiments without diatomite\nis missing.\nResponse:\nWe have revised the relevant section to explicitly state that the estimate of ~11.5 was obtained\nfrom controlled experiments in the absence of diatomite. This clarification can be found in the\nfirst paragraph of the section “Analysis of the contribution of Si”.\nComment 4\nA brief acknowledgment that Cl⁻ ion-specific effects were not explicitly modeled is needed.\nResponse:\nWe have added a brief acknowledgment in the second paragraph of the section “Atomic-scale\ninsights from DFT”, explicitly noting that Cl⁻ ion-specific effects were not included in our\nDFT modeling.\nComment 5\nAn explanation why there are practical limitations of operando XRD characterization in this\nsystem is required.\nResponse:\nWe have added an explanation of the practical limitations of operando XRD characterization\nfor this system in the first paragraph of the section “Origin of robust autocatalytic effect”."}]

Decision letter