bluuebunny/crossref_metadata_2025 huggingface dataset:
3D-Printed Hierarchical Electrodes for Ampere-Level Alkaline Water Electrolysis
Authors: Chen Xiaodong , Zhou Deli , Ding Junhao , Song Xu , Li Weihong
Published: August 2024

In the realm of water electrolysis technology, Alkaline Electrolysis Cell (ALK) hydrogen production stands as a pivotal technology, playing a critical role in the pursuit of large-scale green hydrogen production and the achievement of the "dual carbon" objective. Despite its importance, the mass transfer efficiency of commercial porous nickel electrodes currently used in ALK systems is suboptimal. These electrodes, plagued by unstable catalyst loading, typically operate at current densities between 300-500 mA/cm², seldom reaching the desired threshold of 1 A/cm². This limitation hampers the potential of ALK hydrogen production to satisfy industrial-scale hydrogen production demands.

In the quest to overcome these limitations, the concept of the Triple Periodic Minimum Surface (TPMS) structure, a cellular architecture mathematically defined and prevalent in natural biological forms such as butterfly wings and beetle shells, is introduced. The TPMS's unique geometry is adept at adapting to mechanical requirements for various applications, including structural and fluidic systems. It allows for versatile manipulation of geometric parameters like aperture size, porosity, and tortuosity, thereby substantially broadening the design possibilities for electrode structures and enhancing the efficiency of gas-liquid and electron transfer.

To harness these benefits, we propose the creation of nickel/nickel-iron electrodes using 3D printing technology. These electrodes are characterized by their cross-scale porosity, ordered structure, and adjustable TPMS design. This innovative electrode design significantly augments bubble transport efficiency and mass transfer performance, while also providing additional anchor points for catalysts, thereby enhancing the electrochemical active surface area, intrinsic activity, and stability of the composite catalyst. As a result, these electrodes achieve ampere-level current densities in ALK electrolysis cells, enhancing electrolysis efficiency and reducing energy consumption.

Our methodology involves the use of selective laser melting printing technology to fabricate multi-tier nickel/nickel-iron electrodes of varying specifications. These electrodes are then coated with MOOH catalysts using an electrochemical deposition process. Through rigorous testing and comparison of electrochemical performance parameters, we identified the optimal multi-stage nickel/nickel-iron electrode and its composite catalyst.

Electrochemical performance tests reveal that, compared to traditional commercial porous nickel electrodes, our 3D printed electrodes decrease overpotential by 14% and improve electrolytic cell efficiency by 10% at a current density of 1 A/cm². Furthermore, these electrodes exhibit minimal degradation after a 500-hour durability test. The demonstrated efficiency and durability of these 3D-printed hierarchical electrodes indicate significant potential for their application in ampere-level alkaline water electrolysis.

Figure 1
(Invited) The Latest Developments in Radiation-Grafted Anion-Exchange Membranes
Authors: Periasamy Arun Prakash , Rupesinghe Rosemary , Nash Rebecca , Willson Terrence , Bance-Souahli Rachida , Chakraborty Arup , Wang Lianqin , Whelligan Daniel K , Varcoe John R
Published: August 2024

This invited lecture will discuss the latest developments in radiation-grafted anion-exchange membranes (RG-AEM) that are being developed for a wide range of electrochemical technologies including fuel cells, electrolysers, and reverse electrodialysis.

This presentation will discuss the following key points:

RG-AEMs can have very high conductivities and water diffusivities, however they generally have excessive water uptakes and degrees of swelling in water, as well as poor permselectivities when in contact with aqueous salt solutions.

Crosslinking can reduce swelling and improve permselectivities, but this is at the expense of conductivity.

The cationic headgroup chemistries can alter the water uptakes of the RG-AEMs, which can impact properties such as their alkali stability and permselectivity.

Subtle changes in amination can lead to RG-AEMs with very different water contents and diffusivities.

When fully hydrated, RG-AEMs in the alkali forms can have usefully high stabilities at temperatures above 60oC.

RG-AEMs can be made with multiple chemical functionalities either via the co-grafting of more than one monomer or via amination using more than one amine reagent (see scheme below).

Finally, the presentation will present some recent undergraduate project results that probe the homogeneity of grafting using a new titration technique.

Figure 1
Cyclic Olefin Copolymer-Based Reinforced Anion Exchange Membrane for Fuel Cell
Authors: Park Heemin , Nellepalli Pothanagandhi , Leonard Daniel P , Kim Yu Seung , Bae Chulsung
Published: August 2024

Alkaline exchange membrane (AEM)-based fuel cells have emerged as a promising technology for clean energy conversion. In contrast to acidic proton exchange membrane in fuel cells, AEM fuel cells utilize an alkaline membrane AEM to facilitate the migration of hydroxide ions, offering advantages of economic earth-abundant catalysts and enhanced electrochemical reaction kinetics. However, AEMs that possess all characters of high ion conductivity, good chemical stability under high pH and temperature, robust mechanical properties, scalable synthesis, and low manufacturing costs are rare until now.

Herein, we present quaternary ammonium-functionalized cyclic olefin copolymers (COCs) as a new class of alkaline stable and low-cost AEMs. Furthermore, we developed reinforced composite AEM by impregnating the quaternary ammonium-functionalized COC into a mechanically robust matrix. The prepared COC-reinforced membrane exhibits outstanding hydroxide conductivity of 127 mS/cm at 80°C and low swelling ratio in liquid water, and excellent mechanical properties with a tensile strength > 50 MPa, and elongation at break > 248%. The H2-O2 fuel cell test exhibited a maximum peak power density of >1.2 W cm-2 at 80°C with a low high-frequency resistance (HFR) under 0.1 Ohm cm2.
Lanthanum Transition-Metal Sulfide Electrocatalysts for Overall Water Splitting
Authors: Diaz De la Cruz Germany , Singh Shantanu , Maniyanganam Ahamed Irshad , Zhao Boyang , Zayat Billal , Narayan Sri , Ravichandran Jayakanth
Published: August 2024

Hydrogen has been identified as a sustainable energy source for the future with the potential of replacing fossil fuels due to its high gravimetric energy density and zero carbon emissions. Water electrolysis is a promising approach to the clean production of pure hydrogen, however, the benchmark catalysts of the half reactions of water electrolysis are noble-metal based, which limit the application of this technique.1 As well, the high energy barrier and sluggish kinetics of the oxygen evolution reaction limit the efficiency of the system. Therefore, it is crucial to develop robust, stable, and cost-effective materials for water electrolysis to be scalable. Lanthanum transition-metal oxide electrocatalysts have been pursued in the past for water splitting due to the high abundance of lanthanum and transition metals.2 However, these catalysts suffer from low conductivity and inherent instability towards oxygen evolution. Binary sulfides, selenides, and phosphides have also been pursued,3 but the compositional space of these materials is limited. Ternary sulfides offer a wider compositional space that allows fine-tuning for optimal performance. As a result, we have pursued the synthesis and application of the relatively unexplored ternary chalcogenides, LaMS3 (M = Ni, Co, Fe, Mn) towards water electrolysis. The efficiency of water electrolysis and stability of the materials have been tested with linear sweep voltammetry, galvanostatic measurements, and electrochemical impedance spectroscopy. We found these materials to be active towards both the hydrogen and oxygen evolution reactions, in acidic and alkaline conditions, respectively, with the catalysts exhibiting an activity trend where LaNiS3 > LaCoS3 > LaFeS3 > LaMnS3. For HER, LaNiS3 exhibits an overpotential of 340 mV at 10 mAcm-2 with a Tafel slope of 79 mV/decade. For OER, an overpotential of 373 mV at 10 mAcm-2 and a low Tafel slope of 48 mV/decade are observed. In addition, LaNiS3 proved to be highly stable with minimal change in potential over a period of 18 hours. The high activity and stability of LaNiS3 towards both half reactions of water electrolysis make it a promising candidate for a bifunctional water splitting electrocatalyst.

References

Wang, S.; Lu, A.; Zhong, C.-J. Hydrogen Production from Water Electrolysis: Role of Catalysts. Nano Convergence
2021, 8 (1), 4.

Dias, J. A.; Andrade, M. A. S.; Santos, H. L. S.; Morelli, M. R.; Mascaro, L. H. Lanthanum‐Based Perovskites for Catalytic Oxygen Evolution Reaction. ChemElectroChem
2020, 7 (15), 3173–3192.

Anantharaj, S.; Ede, S. R.; Sakthikumar, K.; Karthick, K.; Mishra, S.; Kundu, S. Recent Trends and Perspectives in Electrochemical Water Splitting with an Emphasis on Sulfide, Selenide, and Phosphide Catalysts of Fe, Co, and Ni: A Review. ACS Catal.
2016, 6 (12), 8069–8097.
Kinetics of Temperature-Modulated Water Splitting: Enhancing Efficiency for Hydrogen Generation Using Cu-Doped Nico-Layered Double Hydroxides
Authors: Kansal Sakshi , R Rahul , Priya Surbhi , Chandra Amreesh
Published: August 2024

Ensuring the efficiency of an electrocatalyst under non-ambient conditions especially at high temperature, is crucial for their facile integration in industrial electrolysers. Varying temperatures governs the thermodynamic and kinetics aspects of water electrolysis by altering reactions rates, conductivity, and adsorption-desorption mechanism. This directly impacts the extent of hydrogen/oxygen evolution reactions (HER/OER). This study demonstrates that the Cu-doped trimetallic NiCoLDHs nanocatalysts shows significant improvement in overpotential ~20% and 10% for OER, and HER, respectively, compared to room temperature electrolysis. Further, to evaluate the effect of elevated temperatures on the kinetics of HER/OER, activation energies were calculated. For HER, the activation energy was found to be 14.4 kJ mol-1, while for OER, it was ~23 kJ mol-1. Density functional theory calculations were carried out to determine the electronic and band structure of the electrocatalysts. The results explains the reasons of increase in their electronic conductivity and electrocatalytic activity for HER/OER at elevated temperatures.

References:

Santos et al., ACS Appl. Mater. Interfaces
2020, 12, 17492−17501.

Piontek et al., ACS Catal. 2018, 8, 987−996.
Applicability of Non-PGM Bi-Functional Electrocatalyst in a Scaled-up Anion Exchange Membrane Water Electrolysis
Authors: Lee Dong-Yeol , Lee Jaeyoung , Kang Sinwoo
Published: August 2024

While non-precious metal catalyst materials are crucial for AEMWE systems, catalyst substances possessing both adequate hydrogen molecule adsorption ability and suitable electrical conductivity and hydrophilicity are still in the developmental stage.

Ni-Mo alloy metals are known as those that have appropriate hydrogen molecule adsorption binding energy, making them excellent electrochemical catalysts for the cathode. However, they suffer from a high content of oxide, which hampers electrical conductivity, and the formation of a high oxidation state of Ni molecules, making hydrogen molecule detachment challenging.

On the other hand, Ni-Fe alloys are recognized for their excellent -OOH group adsorption ability and high electrical conductivity, and that has a low oxidation state Ni phase for high hydrogen desorption ability.

Therefore, in this study, we aimed to synthesize NiMoFe-based alloy catalysts to enhance the hydrogen evolution reaction (HER) activity of Ni-Mo group catalysts while simultaneously increasing the oxygen evolution reaction (OER) activity. Using a hydrothermal synthesis method for NiMoFe catalysts we employed a high-temperature thermal reduction process to minimize the oxide layer that has poor conductivity.

Evaluation of the catalyst activity through half-cell experiments demonstrated low overpotentials in both Overall water electrolysis reactions. Furthermore, an MEA-type experiment was conducted to evaluate the applicability of single-cell.

Furthermore, Stability tests confirmed a stable voltage.

Finally, when compared to the combination of precious metal catalysts, this exhibited superior performance. Therefore, this study suggests that non-noble catalysts could serve as a crucial stepping stone, surpassing PGM metal catalysts in alkaline media.
Producing Hydrogen with Less Energy in Ammonia Electrolyzer Stack Using Pt-Ir Catalyst Dual-Layer Electrode
Authors: Yoon Donghyun , Lee Jaeyoung
Published: August 2024

Electrochemical ammonia decomposition has recently been regarded as a possible future technology for CO2-free hydrogen production. Pt-based catalysts have already known for having excellent activity in ammonia oxidation reactions (AOR) due to the fast dehydrogenation step enabled by the moderate adsorption strengths of nitrogen species [1]. Among them, the incorporation of Ir into Pt notably decreases the activation energy required for ammonia oxidation on Pt, lowing onset potential in alkaline media [2]. Besides, the electrolysis of ammonia has a less energy consumption than water electrolysis because of the lower operating voltage at the Anode [3]. In this study, we fabricated dual-layer electrode containing Pt-Ir catalyst, enhancing the AOR catalytic activity and showing long-term stability. The ammonia electrolysis single-cell with an anion exchange membrane (AEM) was successfully operating and then scaled up to a large area stack cell. We observed that this electrolyzer stack cell produced high-purity hydrogen using less energy than water electrolysis.

Acknowledgements

This research was supported by National R&D Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (NRF-2021K1A4A8A01079455). This work was also supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) [No. 2021R1A5A1028138].

Reference

[1] J. Liu, Z. Liu, Adv. Funct. Mater 2022, 32, 2110702

[2] A. Estejab, G. G. Botte, Comput. Theor. Chem 2016, 1091, 31-40

[3] J. Gwak, M. Choun, ChemSusChem 2016, 9, 403–408
PFAS-Free: Robust and Chemically Stable Ion-Solvating Polymer Membrane Derived from Poly(arylene alkylene) for High-Performance Alkaline Water Electrolysis
Authors: Rajappan Sinu Charamchirail , Xia Yifan , Serhiichuk Dmytro , Kraglund Mikkel Rykær , Aili David , Jensen Jens Oluf Oluf
Published: August 2024

Polymeric ion-solvating membranes1 derived from poly(arylene alkylene)s2 have emerged as promising candidates for alkaline water electrolysis, offering a PFAS-free, robust, and chemically stable alternative. This work focuses on the development of such a membrane with an emphasis on high resistance to gas crossover, addressing the challenges associated with conventional ion-exchange materials.

The polymer membrane presented in this study demonstrated very good performance in alkaline water electrolysis. At 80 degrees Celsius, the membrane exhibits a specific conductivity of 36 mS/cm, underscoring its ion-solvating ability and efficiency in a 20 wt% KOH solution. The electrochemical performance is exemplified by the attainment of a 700-mA current below 2.6V with uncatalyzed nickel foam electrodes, showcasing the superior conductivity and efficiency in facilitating the electrolysis process.

One of the key features of these membranes is their longevity, as evidenced by their ability to operate for more than 200 hours without any discernible voltage decay. This extended operational lifespan underscores the robustness and durability of the developed membranes, making them highly suitable for practical applications in alkaline water electrolysis.

Furthermore, the membranes exhibit a high resistance to gas crossover, addressing a common challenge in electrolysis systems. This property ensures enhanced selectivity and efficiency by minimizing unwanted reactions and improving the overall electrolysis process.

In conclusion, the presented work signifies a significant advancement in the development of ion-solvating polymer membranes derived from poly(arylene alkylene) for alkaline water electrolysis. The membranes not only outperform existing alternatives but also offer a sustainable and environmentally friendly solution by being PFAS-free. The demonstrated high performance, stability, and resistance to gas crossover make these membranes promising candidates for the advancement of alkaline water electrolysis technology, contributing to the development of efficient and environmentally conscious hydrogen production systems.

Keywords: Alkaline; electrolysis; Poly (arylene alkylene)s; membranes; ion-solvating

References:

Aili, D.; Kraglund, M. R.; Rajappan, S. C.; Serhiichuk, D.; Xia, Y.; Deimede, V.; Kallitsis, J.; Bae, C.; Jannasch, P.; Henkensmeier, D.; Jensen, J. O. ACS Energy Lett.
2023, 8, 1900–1910.

Zolotukhin, M. G.; Fomine, S.; Lazo, L. M.; Hernndez, M. D. C. G.; Guzmáln-Gutiérrez, M. T.; Ruiz-Trevino, A.; Fritsch, D.; Cuellas, D. C.; Fernandez-G., J. M. High Perform. Polym. 2007, 19, 638–648.
Sulfone Based Polymers: An Ether-Free and Non-Fluorinated Alternative to Perfluorinated Anion Exchange Membranes in Low Temperature Water Electrolyzers
Authors: Ekennia Anthony Chinonso , Chen Lihaokun , Kwak Minkyoung , Boettcher Shannon W.
Published: August 2024

Several advanced anion exchange membranes have been reported to achieve good ex-situ stability under harsh alkaline conditions without obvious degradation. However, only a handful of them can be stably operated at current densities above 400mA for more than 100hrs in pure water electrolyzers, due to poor oxidative stability. Here we report a series of high-performance non-fluorinated poly(arylene piperidinium sulfone) copolymers (PAPSs) for anion exchange membrane, along with improved pure water AEMWE performance and durability. The copolymers possess high ion conductivity (>130 mS cm-1), good mechanical properties (tensile strength > 80 MPa) and good thermal stability. Moreover, PAPS based AEMWEs reach >100 h in-situ durability under 500 mA cm-2 at 60oC. The presented work provides new non-fluorinated piperidinium cationic based AEMs with improved performance to the fluorinated PAP AEMs for various energy devices.
A Literature Survey of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts
Authors: Kawashima Kenta , Marquez Raul A. , Smith Lettie A. , Vaidyula Rinish Reddy , Carrasco Jaim Omar Ali , Wang Ziqing , Son Yoon Jun , Cao Chi L. , Mullins Charles Buddie
Published: August 2024

Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) are a new class of oxygen evolution reaction (OER) electrocatalysts, which have become a relevant topic for electrocatalytic energy conversion and storage research. This is because of their earth abundance, high electrical conductivity, and resultant high OER performance. Furthermore, some X-ide electrocatalysts demonstrate various degrees of oxidation resistance under OER potentials due to their differences in chemical composition, crystal structure, and morphology. Interestingly, there are three possible post-OER electrocatalyst models: a fully oxidized oxide/(oxy)hydroxide material, a partially oxidized core@shell structure, and an unoxidized material.1 In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Recently, several topical reviews have been published. However, typically these literature reviews have provided limited conclusions targeted at only certain X-ides. Additionally, certain reviews omit key points, especially regarding the “catalytically active species” in X-ide OER electrocatalysts.

In this work, we provide a comprehensive summary of (i) the experimental parameters (e.g., substrates, electrocatalyst loading amounts, electrocatalyst shapes, geometric overpotentials, Tafel slopes, etc.) and (ii) the details of the electrochemical stability tests and following post analyses used in all the X-ide OER electrocatalyst publications from 2013 (the birth of this research area) to 2022.2 In particular, based on the reported post-OER analytical results, we attempt to exhaustively classify all the X-ide electrocatalysts into four groups: no oxidation, partial oxidation, full oxidation, and unknown, which is relevant to the nature of the “catalytically active species” in X-ide OER electrocatalysts. After investigating the simpler X-ide systems, transition metal-based polyanion compounds/composites are also surveyed. Finally, we introduce the reported novel and special analytical techniques employed for observing X-ide reconstruction (i.e., oxidation and other phase transformations) during OER testing, which can be useful in selecting the analytical technique of maximum utility for the researchers’ purpose. Additionally, for each material sub-group (e.g., borides, carbides, nitrides, phosphides, sulfides, selenides, and tellurides), we also point out further challenges to be addressed and propose further questions yet to be answered, which may provide clues pointing to future research tasks.

References

B. R. Wygant, K. Kawashima, and C. B. Mullins, ACS Energy Lett., 3, 2956–2966 (2018).

K. Kawashima et al., Chem. Rev., 123, 12795–13208 (2023).
(Invited) IrOx Nanoparticle Catalysts on a Unique Microstructure of Doped Tin Oxide to Dramatically Boost the Oxygen Evolution Reaction Activity for PEM Water Electrolysis
Authors: Kakinuma Katsuyoshi
Published: August 2024

Proton exchange membrane water electrolyzers (PEM WEs) has a potential to produce high-purity green hydrogen. PEMWEs have been commercialized with the use of high loadings of the noble metal Ir-based anode catalyst for the oxygen evolution reaction (OER). To lower the Ir loading amount, it is critically important to develop efficient catalysts with increased Ir utilization and higher OER activity. One-dimensional Ir oxide nanorod/nanoparticles catalysts supported on doped SnO2 with a unique microstructure were invented to show their exceptionally high activity in the OER catalysis, with the Ir-mass specific activity being 10 times higher than that of commercial IrOx catalyst at 1.5 V vs. RHE.[1] The experiment also found that the OER activation energy was greatly lower than that of commercial Ir oxide. The interaction between Ir oxide nanorod/nanoparticles and doped SnO2 support occurs a lower degree of Ir oxidation which allows the surface terminal oxygens to be closer together while allowing facile desorption of nonreactive oxygenated species. The electronic state of Ir oxide nanorod/nanoparticles catalysts could play an important role in facilitating the crucial step of the OER, thereby enhancing the OER activity. These priorities of the catalysts would promise the reduction of the Ir usage in PEMWEs.

Reference

[1] G. Shi, T. Tano, D.A. Tryk, T. Uchiyama, A. Iiyama, M. Uchida, K. Terao, M. Yamaguchi, K. Tamoto, Y. Uchimoto and K. Kakinuma, ACS Catalysis, 13 (2023) 12299.

Figure 1
Engineering the PEM Water Electrolysis Anode for Better Interfacial Electrical Conductivity
Authors: Doo Gisu , Lee CHangsoo , Kim MinJoong , Lee Sechan , Park Hyeonjung , Kim Hee-Tak , Cho Hyun-Seok
Published: August 2024

In pursuing cost-effective green hydrogen production via proton exchange membrane water electrolysis (PEMWE), the high expense of the iridium (Ir)-based oxygen evolution reaction (OER) catalysts poses a significant challenge. To overcome this issue, researchers have focused on developing active OER catalysts and catalyst layers (CLs) with minimum uses of Ir. However, they frequently encountered performance problems at the single-cell level that originate not only from the kinetic polarization but also from the ohmic polarization. In this aspect, we have focused on identifying the reasons for the poor performance of low IrOx-loaded anodes, with loadings as low as 0.10 mg cm-2. We pinpoint the cause of the poor performance of the low loaded anodes to an electron transport problem within the native oxide on the Ti porous transport layer (PTL). Our analysis, grounded in the metal-insulator band model, reveals that the primary factors contributing to electron conductivity loss in the Ti oxide are the upward band bending induced by the Schottky contact with high work function IrOx and by the pinch-off effect from the extensive ionomer contact. Based on the above understanding, we propose an anode CL composed of a one-dimensional iridium catalyst, fabricated by electrospinning and calcination processes. Our nanofiber-based CL effectively mitigates the electron transport problem of the native Ti oxide. This improvement stems from the low work function of the Ir nanofiber catalyst and the highly porous structure that reduces the ionomer contact with the Ti oxide. Furthermore, the highly porous nature of the nanofiber-based CL enhances two-phase mass transport, facilitating the high current operation. These findings underscore the critical role of the CL/PTL interface of the PEMWE anode and present the necessity of a well-structured CL to achieve efficient and cost-effective water electrolysis.
Water Management in Anion Exchange Membrane Fuel Cells Via Distribution of Relaxation Times Analysis
Authors: Haodong Huang , Zeng Lin , Zhao Tianshou
Published: August 2024

In response to growing concerns regarding air pollution and energy scarcity, anion exchange membrane fuel cells (AEMFCs) have emerged as a promising technology for power generation due to their high efficiency, zero emissions, and the abundance of hydrogen resources. Within AEMFCs, water serves as a reactant, being consumed at the cathode, and generated at the anode, which can lead to an imbalance in the water content within the fuel cell. Maintaining an appropriate water distribution is essential for efficient charge transport and electrochemical reaction kinetics. Therefore, the development of a comprehensive water management strategy is crucial to ensure the stable operation and durability of AEMFCs.

Characterizing the water condition of the anode and cathode in different operation conditions (normal, drying, or flooding) is a critical step that provides data foundation for devising effective water management control strategies. Electrochemical impedance spectroscopy (EIS) offers a means to investigate different resistances (kinetics, mass transport, and ohmic losses) over varying time scales during operation to assess water transport. The conventional interpretation of EIS data typically relies on equivalent circuit models, necessitating prior assumptions and initial component selections. In this study, we employed the distribution of relaxation times (DRT) methodology, known for its powerful ability to separate components, to conduct a more precise analysis of polarization processes. Initially, electrochemical impedance dynamics related to hydroxide transport, hydrogen oxidation reactions, and oxygen reduction reactions were effectively extracted. Subsequently, DRT was employed to investigate the loss and variation trends of each polarization process under conditions of anode and cathode water flooding and drying conditions, respectively. Furthermore, to gain a deeper understanding of the effects of water content on mass transport and electrochemical reaction kinetics, a three-dimensional multi-physics model for AEMFCs was developed. This model incorporated water phase transition, heat and mass transfer, liquid water and dissolver water transport, and electrochemical reactions. These endeavors represent a comprehensive and systematic approach to guide the utilization of the distribution of relaxation times in fuel cells.
How Bulk Versus Surface Chemistry Affects the Surface Reconstruction of Perovskite Nickelates and Their Activation By Fe Impurities
Authors: Twight Liam , Boettcher Shannon W.
Published: August 2024

Whether surface reconstruction of LaNiO3 and the related Ruddlesden-Popper oxide La2NiO4 occurs during the oxygen evolution reaction has only recently emerged as a topic of rigorous study despite the implications this would have for its activity and stability at scales from the three-electrode cell to electrolyzer stacks. Correlation of structure to reconstruction propensity is much needed, but not well-understood. Building off of our work suggesting that these oxides do electrochemically reconstruct to the thermodynamically stable, amorphous, Fe impurity-sensitive, nickel hydroxide, we extend our observations to materials doped with alternative rare earth and alkaline earth metal cations at the La-site. First, we find that undoped La2NiO4 has a higher tendency to reconstruct, forming almost twice as much Ni(OH)2 for a given electrochemical treatment as LaNiO3 which we attribute to differences in Ni valence state between the two materials. This leads to a higher current density when exposed to Fe impurities by formation of more NiFeOxHy, the highest activity catalyst for OER known. Yet, the intrinsic activity of the Fe sites formed are equivalent within experimental error suggesting a convergence in surface composition despite different bulk composition. We find this reconstruction also occurs for doped materials, extending the library of materials expected to have dynamic surfaces during OER. Further, we use XPS coupled with argon ion sputtering to connect differences in reconstruction extent to the bulk and surface composition, with particular emphasis on the valence state of nickel as a possible descriptor.
Ag/Nico LDH Heterogeneous Structure for Efficient Alkaline Oxygen Evolution
Authors: Shao Minhua , Sun Yan
Published: August 2024

Hydrogen is regarded as an ideal energy carrier owing to the highest energy density, presenting the possibility of substituting for traditional fossil fuels. Nowadays, water splitting is significant in producing large-scale hydrogen. However, the sluggish reaction kinetics during anodic OER, caused by the four-electron transfer, has hindered this energy conversion strategy. Although IrO2 and RuO2 are currently the representative OER electrocatalysts, their high cost and unsatisfactory performance limit their commercial application.

Numerous electrocatalysts, including oxides, hydroxides, high-entropy alloy, metal organic frameworks, and their hybrids, have been developed to address this issue. Among them, layered double hydroxides (LDH) have demonstrated outstanding performance due to their highly adjustable structure, powerful host-guest interaction, and single-atomic-like active sites. NiCo LDH has attracted significant attention because of its appropriate atomic and electronic structure, intrinsic active sites and defects, compared with single-type Ni-based or Co-based catalysts. However, to meet the requirements of industrial production, a simple and scalable method to synthesize electrocatalysts with favorable OER activity and stability is imperative.

We propose a facile and scalable strategy to synthesize Ag-decorated NiCo LDH (Ag/NiCo LDH) by electrodeposition and subsequent spontaneous redox reaction. A spontaneous redox reaction driven by the difference in standard redox potential of reactants can be applied to prepare heterogeneous catalysts in consequence of the facile process, tight combination between substrate and decorated materials, and no supplementary energy input. Silver metal, with its appropriate standard redox potential, good conductivity, and low cost compared to Iridium and Ruthenium, serves as a suitable decorated material. This strategy provides several advantages, for example, Ⅰ) optimizing the electronic structure of Ni and Co by the charge transfer from Ni, Co to Ag; Ⅱ) exposing more active surface area because of the heterogeneous structure, Ⅲ) improving the charge transfer capacity owing to the excellent conductivity of Ag nanoparticles, Ⅳ) increasing the stability of NiCo LDH due to the tight combination of Ag and NiCo LDH, Ⅴ) lowering the catalysts' price compared with Iridium and Ruthenium.

The synthesized Ag/NiCo LDH exhibits enhanced OER performance in 1M KOH electrolyte, achieving an overpotential of 440 mV at a current density of 1000 mA cm-2
geo, surpassing that of NiCo LDH (722 mV at 1000 mA cm-2
geo). Surprisingly, Ag/NiCo LDH demonstrates exceptional durability, lasting over 425 h at 1000 mA cm-2
geo, an improvement of nearly eight-fold compared to NiCo LDH (50 h). This study provides a promising approach for developing efficient and stable electrocatalysts for alkaline oxygen evolution.
Stability of Bipolar Plates in Proton Exchange Membrane Water Electrolysis: Dissolution Studies of Titanium and Stainless Steel
Authors: Fiedler Lena , Ma Tien Ching , Fritsch Birk , Risse Jan Henning , Lechner Michael , Dworschak Dominik , Merklein Marion , Hutzler Andreas , Mayrhofer Karl J. J.
Published: August 2024

Due to its high current densities and fast system response proton exchange membrane water electrolysis (PEMWE) is an ideal system for green hydrogen production from renewable energies. However, its widespread use is still hindered by the high costs rendering the produced green hydrogen not competitive. Therefore, a cost reduction is highly needed. The bipolar plates (BPPs) are causing a colossal factor in material costs. They are usually produced from titanium and coated with even more expensive materials such as gold or platinum. A possible, cheaper alternative is stainless steel. However, it is suspected to suffer from corrosion leading to the leaching of cations that can poison the catalyst or membrane.[1] Thus, we investigated the stability of BPP materials, the currently used titanium, and its cheaper alternative stainless steel (316L).[2]

Therefore, we use a modified scanning flow cell setup coupled to an inductively coupled plasma mass spectrometer for investigating the stability of both materials on-line, as well as with scanning electron microscopy. To mimic the conditions at the BPP under operation, deionized (DI) water and highly diluted (0.5 mM) H2SO4 are chosen as electrolytes combined with a sample temperature of 60 °C.

For Ti, we show that the dissolution is negligible, whereas 316L corrodes. For 316L, in DI water mainly Cr dissolves, while in the H2SO4 solution, the dissolution is more pronounced, and all alloy components are detected. Besides the pH value, the applied potentials play a crucial for its stability. However, our findings suggest that the contamination for a typical full cell architecture remains below 1 ppm, even for the highest measured dissolution rate of SS 316L.

These capabilities of on-line high-throughput stability tests for BPP materials are, furthermore, used to investigate the influence of contaminations, such as F- or Cl-, and of the temperature-dependence on the stability of 316L. These results give further insights into 316L stability as BPP material and therefore contribute to the development towards cost-effective PEMWE.

[1] a) N. Rojas, M. Sánchez-Molina, G. Sevilla, E. Amores, E. Almandoz, J. Esparza, M. R. Cruz Vivas, C. Colominas, Int. J. Hydrogen Energy
2021, 46, 25929-25943; b) H. Becker, J. Murawski, D. V. Shinde, I. E. L. Stephens, G. Hinds, G. Smith, Sustain.
Energy Fuels
2023, 7, 1565-1603.

[2] L. Fiedler, T. C. Ma, B. Fritsch, J. H. Risse, M. Lechner, D. Dworschak, M. Merklein, K. J. J. Mayrhofer, A. Hutzler, ChemElectroChem
2023, e202300373.

Figure 1
MFe2O4 (M: Cu, Ni)/SnS2magnetic Core-Shell Heterostructure for Photocatalytic H2 Generation and Environmental Remediation
Authors: Zala Devanshi , Mukhopadhyay Indrajit , Ray Abhijit
Published: August 2024

Overgrowing demand for sustainable energy sources and environmental remediation has driven extensive research in the field of photocatalysis. This study presents a hydrothermal synthesis of a novel MFe2O4 (M: Cu, Ni)/SnS2 magnetic core-shell heterostructure. The engineered heterostructure combines the unique properties of MFe2O4 (M: Cu, Ni) magnetic crystal as a core with SnS2 nanosheets as a shell, aiming to exploit type-2 heterojunction properties to improve effects for improved photocatalytic performance. The structural chemistry, phase formation, and crystal orientation of the prepared material are investigated using various analytical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, and FTIR Spectroscopy. FE-SEM analysis reveals a well-defined core-shell morphology with intimate interfaces between MFe2O4 (M: Cu, Ni) crystals and SnS2 nanosheets. Photocatalytic efficiency is assessed through the industrial dye degradation process. The influence of the heterostructure's structural features on the photocatalytic activity is explored through density function theory, emphasizing the role of the core-shell interface and the magnetic properties of MFe2O4 (M: Cu, Ni) cores. The chemistry between the magnetic core and the shell in the heterostructure is demonstrated to be crucial for optimizing charge carrier dynamics and promoting surface reactions. Photocatalytic H2 generation under artificial simulated sunlight irradiation in the presence of MFe2O4 (M: Cu, Ni)/SnS2 core-shell heterostructure is demonstrated. This study not only presents a novel MFe2O4 (M: Cu, Ni)/SnS2 heterostructure for photocatalytic H2 generation but also provides valuable insights into the intricate relationship between structural chemistry and photocatalytic efficiency. The engineered heterostructure shows promising potential for applications in sustainable energy production and environmental remediation, contributing to the ongoing efforts towards a cleaner and more sustainable future.
Photocatalytic Methane Oxidation and Removal Mediated by Free Radicals
Authors: Wan Gang , Majumdar Arun
Published: August 2024

Activation and selective oxidation of C-H bond in methane under mild conditions constitutes long-standing challenges which are of fundamental and technological importance, from biological to industrial and environmental. Earth relies on free radicals to remove the climate-damaging methane and other organic pollutants from the air. In recent decades, intensive efforts have been focused on leveraging free radicals for selective methane oxidation. Free radicals are one of key mediators underpinning many active sites in thermal catalysis and these enhancement effects induced by the light and electric fields. However, it remains unclear how free radicals as active species mediate the C-H bond activation in methane and dictate the products distribution.

In this talk, we will discuss our recent advances in understanding and promoting the photocatalytic oxidation of methane to methanol by combining the rational design of photocatalysts, photochemical experiments, as well as the in-situ electron paramagnetic resonance studies of free radicals. Our results unravel interactions between these free radicals and the solid co-catalysts, ions, and gases molecules in water, as well as their impact on methane removal and its selective oxidation. Our studies highlight the neglected while important interplay between photogenerated radicals and co-catalysts, ion impurities, and gas molecules in promoting methane removal and controlling the products distribution. Furthermore, we report an inherent trade-off in the photochemical methane to methanol conversion. A new design principle featuring isolating different reaction steps is developed to circumvent this trade-off.

Such molecular-level insights into photocatalysts and their interactions with free radicals are expected to promote the methane removal and its selective functionalization and offer informative design principles for chemical bonds activations that are driven by light, heat, and electric fields.
(Invited) Electrochemistry and Operando Spectroscopy of the Upgrade of CO2/CO to Fuels and Chemicals
Authors: Sargent Edward Hartley
Published: August 2024

I will discuss recently progress in performance of electrified ~ ambient-temperature CO2/CO to chemicals and fuels such as ethylene. I will include reference to operando spectroscopies that seek to report on the chemical state of the catalyst active sites and also of the intermediates/reaction pathways.
(Invited) Photocatalysis from Plasmonic Metals to Plasmonic Semiconductors
Authors: Wu Nianqiang
Published: August 2024

This talk will introduce our work in photocatalysis spanning from plasmonic metals to plasmonic semiconductors. First, we will discuss common features and differences in generation, energetics and lifetime of plasmonic hot electrons and holes created in plasmonic metals to plasmonic semiconductors. Second, we will investigate how plasmonic hot carries generated in metals and semiconductors drive photocatalysis. Third, we will explore the energy transfer from plasmonic materials to non-plasmonic semiconductors.
(Invited) Near Field Photocatalysis for Site-Selective Reactions By Using ZnO Nanoplates
Authors: Tatsuma Tetsu , Lee Seung Hyuk , Oba Yuki , Horiuchi Genki
Published: August 2024

Nanofabrication is a technology for control of the morphology, orientation, and configuration of nanomaterials. When ordinary, propagating light is employed as a processing tool, subwavelength fabrication is difficult due to the diffraction limit. However, if optical near field, which is localized in a subwavelength region is used, nanofabrication beyond the diffraction limit is possible.

We have demonstrated that subwavelength nanofabrication is possible by taking advantage of the optical near field. Since hot electron-hole pairs are generated at around the plasmonic resonance sites, the energetic carriers can be used to drive oxidative dissolution of Ag,1,2 oxidative deposition of PbO2,3,4 and reductive deposition of Ag,5 in a site-selective manner. These techniques have been applied to subwavelength photochromic data storage,1,2 fabrication of chiral nanoparticles,4-7 and site-selective modification of a plasmonic photocatalyst with a co-catalyst.8

Generation of optical near field is possible even at non-plasmonic, semiconducting or dielectric nanostructures. Here we employed In-doped ZnO (In:ZnO) as a semiconductor photocatalyst. Hexagonal In:ZnO nanoplates were synthesized and adsorbed onto a glass substrate, and irradiated with linearly polarized UV light in the presence of Ag ions for reductive deposition of Ag. The optical near field generated under polarized UV light gave rise to site-selective Ag deposition. Also, the sample exhibited linear dichroism (LD) signals, indicating that the nanoparticles have optical anisotropy. On the other hand, unpolarized UV light gave no optical anisotropy. Electromagnetic simulations successfully reproduced the LD spectra. We have also performed site-selective oxidation reactions by using the hexagonal In:ZnO nanoplates.

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(Invited) Probe the Reaction Intermediates on Noble Metal Electrodes during Oer with Vibrational Sum Frequency Spectroscopy
Authors: Yang Yuke , Gerke Felix , Yang Tao , Campen R. Kramer , Tong Yujin
Published: August 2024

Electrochemical water splitting on noble metal surface is an important reaction of both fundamental and application interest. It is well known that the bottleneck of this reaction is the poor kinetics for oxygen generation from water oxidation. Despite of years study, the mechanisms in terms of the roles of the thin oxides film that formed on the metal surface before/during oxygen evolution are still inexplicit. One of the main reasons is the lack of molecular level information about the oxide thin film structures. In this study, we investigated the electrochemical oxidation of gold and platinum in solutions with different pHs by employing surface specific vibrational sum frequency spectroscopy (VSFS)1-3. By analyzing the potential dependent behaviors of different types of adsorbed species, we could gain molecular level information regarding the structures and formation mechanisms of metal-oxides. The results of this study will provide essential data toward understanding the oxygen evolution mechanism and also suggest strategies for developing better water splitting catalysts.

[1]. Zhang, I. Y.; Zwaschka, G.; Wang, Z.; Wolf, M.; Campen, R. K.; Tong, Y., Resolving the chemical identity of H2SO4 derived anions on Pt(111) electrodes: they're sulfate. Physical Chemistry Chemical Physics 2019, 21 (35), 19147-19152.

[2]. Zwaschka, G.; Wolf, M.; Campen, R. K.; Tong, Y., A Microscopic Model of the Electrochemical Vibrational Stark Effect: Understanding VSF Spectroscopy of (bi)Sulfate on Pt(111). Surf. Sci. 2018, 678, 78-85.

[3]Gong, X.; Campen, R. K.; Tong, Y. Direct Observation of the Potential-Dependent Protonation and Reorientation of 4-(Dimethylamino)pyridine on Gold Electrodes. J. Phys. Chem. C 2023, 127 (33), 16615-16622. DOI: 10.1021/acs.jpcc.3c03038.
(Invited) Manipulating Interfacial Electrochemistry with Moiré Superlattices
Authors: Bediako Daniel Kwabena
Published: August 2024

At electrode–electrolyte interfaces, crystallographic defects are frequently implicated as active sites that mediate interfacial electron transfer (ET) by introducing high densities of localized electronic states (DOS). However, conventional defects are challenging to deterministically synthesize and control at an atomic level, hindering the direct study of how electronic localization impacts interfacial reactivity. Azimuthal misalignment of atomically thin layers produces moiré superlattices and alters the electronic band structure, in a manner that is systematically dependent on the interlayer twist angle. Using van der Waals nanofabrication of two-dimensional heterostructures, scanning electrochemical cell microscopy measurements, and four-dimensional scanning transmission electron microscopy, we report a strong twist angle dependence of heterogeneous charge transfer kinetics at twisted bilayer and trilayer graphene electrodes with the greatest enhancement observed near the ‘magic angles’. These effects are driven by the angle-dependent engineering of moiré flat bands that dictate the electron transfer processes with the solution-phase redox couple, and the structure of the relaxed moiré superlattice. Moiré superlattices therefore serve as an unparalleled platform for systematically interrogating and exploiting the dependence of interfacial ET on local electronic structure.
Molecule-Derived Coatings Improve the Selectivity and Durability of CO2 Reduction on Chalcogenidephotocathodes
Authors: Haber Joel
Published: August 2024

Direct solar-driven conversion of carbon dioxide to chemicals and fuels requires identification of efficient, durable, and selective photocathodes. Chalcogenide p-type semiconductors, exemplified by chalcopyrite Cu(In,Ga)Se2

(CIGS), have been effectively deployed as photocathodes. However, selectivity toward CO2 reduction and durability of the commonly used CdS buffer layer remain unsolved challenges. We have demonstrated that for the wide band gap CuGa3Se5 chalcopyrite absorber these challenges are well addressed by an organic coating generated in situ from an N,N′-(1,4-phenylene)bispyridinium ditriflate salt in the electrolyte. The molecular additive provides a 30-fold increase in selectivity toward CO2R productscompared to the unmodified system and lowers Cd corrosion at least 10-fold. This dual functionality highlights the promise of hybrid solid-state-molecular photocathodes for enabling durable and efficient solar fuel systems.This presentation will highlight the variations in product selectivity and durability observed for different combinations of coatings derived from molecular precursors in the electrolyte with photocathodes includingCuGa3Se5 and Cu(In,Ga)Se2, with and without CdS buffer layers.