bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Entropy Alloys as Oxygen Reduction Reaction Electrocatalysts for Proton Exchange Membrane Fuel Cells Application
Authors: Wan Daniel , Chen Guangyu , Yan Jay , Wang Feng , Shao Minhua
Published: February 2024

High entropy alloys (HEA) are complex multi-element materials. Owing to their multi-elemental nature, they can finetune surface adsorption energy and active sites which make them appealing to various catalytic reactions. HEI is a subclass of HEA that consist of an ordered alloy structure rather than a random alloy structure. The order-ness may induce more stable structures and uniform active sites, which in turn enhance the durability and activity under catalytic conditions. Here, we have synthesized a HEI(Pt40Ni20Co20Mn10Ir10) supported on porous carbon via a seed-mediated impregnation method. The intermetallic characteristics with periodic trends can be seen in the HAADF-STEM image (Fig. 1a). Based on the atomic arrangement, the HEI resembled a L12 structure. The corresponding EDX mapping the catalyst also showed the presence of all alloying species in the nanoparticles. The catalyst performance of the catalysts was evaluated in a 3-electrode liquid cell set-up with catalyst coated glassy carbon rotating disk electrode, Ag/AgCl and Pt mesh as working, reference and counter electrode, respectively. The catalyst’s mass activity (MA) was calculated based on the result obtained from ORR polarization test conducted under O2 saturated 0.1M HClO4. The initial mass activities for PtCo and HEA in ORR were 0.81 and 1.23 A mg-1
Pt, respectively (Fig. 1b), while that of Pt/C was only 0.26 A mg-1
Pt. A subsequent accelerated degradation test (ADT) was conducted under Ar-saturated 0.1M HClO4 with 0.6-1.0 V vs RHE square-wave cycling (3s hold at each potential) for 30k cycles. MA was measured after 10k and 30k cycles. HEA retained a MA of 0.48 A mg-1
Pt after the ADT, above the DOE target (0.44 A mg-1
Pt). We also compared our HEI samples synthesized with different annealing temperatures and duration (Fig. 1c), and it showed that 800◦C with 20 mins temperature hold showed the highest MA and electrochemical surface area (ECSA).

Extended X-ray absorption spectroscopy (EXAFS) for the catalyst has also been conducted to further elucidate the structural-performance relationship of HEI (Fig.1d). From Pt L3 edge EXAFS fitting, the fitted R space showed that the Pt-Pt bond length was around 2.704 ± 0.004 Å, which was same as that of the PtCo (Fig. 1e). Therefore, it is believed that both HEI and PtCo has the same strain effect but HEI possessed stronger ligand effect than PtCo due to its unique Pt-M coordination, hence resulting in superior ORR performance over PtCo and Pt.

Figure 1
Fabrication of Self-Standing Porous Foam-like PdM (M = Ni, Fe, Co) Nanocrystals for Boosted Ethanol Oxidation Electrocatalysis
Authors: Abdullah Aboubakr M. , Ipadeola Adewale Kabir , Salah Belal , Eid Kamel
Published: February 2024

Rational designing of self-standing porous foam-like PdM (M = Ni, Fe and Co) nanocrystals was achieved by a fast aqueous-solution method via the co-reduction of metal precursors using sodium borohydride. This was based on the crystallites’ coalescence growth mechanism, including quick nucleation of Pd that served as starting seeds for the nucleation of M, which attached directly along the specific crystallographic and lowered its high surface energy by diffusion of PdM atoms across the interface via Brownian motion to afford self-standing porous foam-like PdM nanocrystals. Amongst the as-prepared PdM nanocrystals, PdNi nanocrystals showed a superior alkaline ethanol oxidation reaction (EOR) activity and stability compared to PdFe, PdCo, Pd nanospheres (Pd-NSs) and commercial Pd/C (10 wt.%) catalysts. The EOR mass activity of PdNi was 1.32, 1.51, 2.01 and 24.05 times than those of PdFe, PdCo, Pd-NSs and Pd/C, respectively based on equal Pd mass. This was attributed to the lower synergistic effect in PdNi, which enhanced H2O activation/dissociation to give OH- species needed for rapid EOR kinetics, meanwhile, the porous foam-like morphology improved electron mobility and increased accessible active sites. This study revealed that low synergism in porous PdM nanocrystals is beneficial for enhancing the EOR activity and durability, which may allow the design of other binary Pd-based alloys for various electrocatalytic reactions.
Dramatic Electrochemical Tuning of the Plasmonic Spectrum of a Metal Nanoparticle on a Mirror
Authors: Vaskevich Alexander , Chuntonov Lev , Basu Arghyadeep , Kaplan-Ashiri Ifat , Haran Gilad
Published: February 2024

Enhancement of electric fields in the nanometric gap between plasmonic nanostructures is widely exploited for sensing, enhanced spectroscopies and photochemistry. Plasmonic properties of nanostructures with ultrathin gaps, such as nanoparticles (NPs) positioned on a flat metal surface (a mirror), have attracted much attention in recent years [1]. We studied the effect of electrochemical control on the plasmonic properties of single Au and Ag NPs on a mirror. We found that the coupled plasmonic resonance could be reversibly tuned over a range of tenths of nanometers, more than an order of magnitude higher than expected based just on capacitive charging of the NPs.

Our experimental system consisted of single Au or Ag NPs (50 nm – 100 nm) adsorbed on a self-assembled monolayer (SAM) of either polyelectrolytes, cysteamine (CEA) or ethanedithiol (EDT) deposited on an atomically flat 100nm thick Au electrode prepared by template stripping. The NPs were either bare (prepared by H2 reduction) or citrate-stabilized and the system was immersed in a basic solution.

Coupling to the mirror electrode resulted in the appearance of several bands in the plasmonic spectrum of individual NPs, as measured by dark-field microspectroscopy (Fig. 1a), and the lowest-energy band could be attributed to the coupled plasmon. Variation of the electrode potential generated a giant, though reversi shift of the spectrum. A plot of the peak position of the coupled plasmon band displayed an S-shaped, phase-transition like behavior (Fig. 1b).

This remarkable result could not be observed with individual NPs deposited on non-metallic surfaces, and can therefore be attributed to a dramatic modulation of the coupling between the particles and the mirror with electrode potential.

Figure 1. Scattering spectra (a) and variation of the spectral position of the coupled plasmon peak (b) of bare AuNP (ca. 60 nm) on CEA/Au electrode. Inset in (a): Scheme of NP on the mirror.

References

[1] J. J. Baumberg, J. Aizpurua, M. H. Mikkelsen, D. R. Smith, Nature Materials
2019,18, 668,

Figure 1
Electrochemical Reduction of Nitrate to Ammonia Using Copper Oxide Catalysts
Authors: Kwon Taesung , Cho Hyeon Beom , Nam Ki Min
Published: February 2024

The electrochemical conversion of nitrates to ammonia offers a promising alternative to the energy- and resource-intensive Haber-Bosch process while simultaneously removing nitrates, a common water pollutant. However, this process is hindered by the eight-electron reduction required to convert nitrate to ammonia, as well as competing hydrogen evolution reactions and other nitrate reduction pathways. Efficient catalysts are essential to address these challenges, and recent studies suggest that oxide catalysts with oxygen vacancies can optimize adsorption energies of intermediates and improve catalytic performance. Copper oxides with oxygen vacancy display high ammonia selectivity in nitrate reduction, but the complexity in vacancy enrichment and the inferior hydrogen adsorption on oxides make nitrate reduction an inefficient process.

In this study, a CuOx composite electrode was synthesized using the hydrothermal method, and its performance was evaluated for efficient conversion of nitrate to ammonia. The synthesized CuOx nanostructure was characterized using X-ray diffraction to determine phase purity and crystal structure, while surface morphology of prepared samples was examined with high resolution transmission electron microscope. The results of X-ray photoelectron spectroscopy suggested that there were abundant oxygen vacancies on the surface of the CuOx, which can act as nitrate adsorption sites. The obtained CuOx composite electrode performs at a high ammonia Faradaic efficiency of over 80% and long-term stability due to interfacial coupling effects. These findings highlight the potential of CuOx catalysts for electrochemical nitrate reduction, offering new opportunities for sustainable nitrogen management and water treatment.
Revealing the Ambience-Dependent Structural Evolutions of Mo–Based Metal–Organic Frameworks with in Situ TEM for Efficient Electrocatalytic N2 Reduction to NH3
Authors: Hsiao Kai-Yuan , Lu Ming-Yen
Published: February 2024

The electrocatalytic nitrogen reduction reaction (NRR) has been demonstrated to be the potential alternative strategy for NH3 production in the clean and sustainable manner. Various materials have been widely adopted for the NRR in recent years, and metal-based zeolite imidazole framework-8 (ZIF-8) and their derivatives have been extensively utilized. In this study, we used in situ TEM to probe the structural evolution of Mo-based zeolite imidazole framework-8 (Mo-ZIF-8) and provide the decomposition mechanism under various pyrolysis conditions [Figure 1a]. Upon pyrolyzing Mo-ZIF-8 under oxidative, inactive, and reductive environments, the ZIF-derived ZnO, Mo2C, and Mo nanoparticles (Mo-NPs) in porous N-doped carbon (PNC) are formed, respectively [Figure 1b]. At a lower concentration of Mo, Mo single atoms (Mo-SAs) were formed in the inactive environment, whereas Mo nanoclusters (Mo-NCs) were obtained under the reductive conditions [Figure 1b]. Furthermore, the Mo-related materials/PNC were served as the catalysts for the electrochemical NRR [Figure 1c]. Among all of the Mo-related materials, Mo-SA/PNC achieves a maximum NH3 yield rate [Figure 1d] and outstanding Faradic efficiency (FE) [Figure 1e] at -0.2 V ( vs. RHE), which is 1.4-fold and 8-fold higher than that of the Mo-NP/PNC, respectively. Our findings suggest some new guidelines for the rational design of the derivatives of metal-based metal–organic frameworks and their feasible application in various field.

Figure 1
Utilizing the Complexity of Transition Metal Phosphide Surfaces to Tune Nitrate Reduction Selectivity
Authors: Nishiwaki Emily , Kuo Ding-Yuan , Cossairt Brandi Michelle
Published: February 2024

Electrocatalytic nitrate reduction (NO3RR) is one exciting method of upcycling nitrate in wastewater by conversion to ammonia, an essential component in fertilizers and a potential liquid fuel. Nitrate reduction to NH3 is impeded by the formation of other products such as NO2
- or H2 via the hydrogen evolution reaction (HER). Transition metal phosphide (TMP) nanocrystals have a non-uniform surface charge distribution due to their binary compositions, which leads to a variety of active sites with different binding affinities. We hypothesize that the diversity of active sites on Ni2P can be leveraged to perform complex electrocatalytic reactions such as the NO3RR. Specifically, a diversity of surface sites can create local active site motifs that promote the adsorption of different intermediates, e.g., *NO3
- and *H, that can readily react for the NO3RR. We prepare 5 nm Ni2P and Ni nanocrystals using colloidal syntheses and deposit them onto a carbon support to compare the simpler catalytic surface of Ni with the more complex Ni2P surface. We compare their NO3RR activities with cyclic voltammetry in neutral, buffered aqueous conditions. We also investigate the selectivity between the NO3RR and HER with bulk electrolysis coupled with a colorimetric assay, where Ni2P on carbon shows higher selectivity toward NH3 over NO2
- and H2. With these experiments, we evaluate our hypothesis that the surface complexity of Ni2P will lead to enhanced NO3RR selectivity relative to Ni. This work sets the stage for developing selective electrocatalysts by utilizing ensembles of active sites to drive electrocatalytic selectivity.
“Dewetted” Metal Nanoparticles As a Platform to Study Electrocatalytic Reactions
Authors: Harsha Shreyas , Sharma Rakesh , Dierner Martin , Casanova Andrea , Baeumer Christoph , Makhotkin Igor , Mul Guido , Ghigna Paolo , Will Johannes , Spiecker Erdmann , Altomare Marco
Published: February 2024

Metal nanoparticles (NPs) are key for catalytic applications such as electrocatalysis. Besides morphology and composition, also structural features largely affect their performance [1]. Recent work uncovered correlations between exposed facets [2,3] and grain boundaries’ density [4,5] with nanoparticles’ activity, selectivity, and stability.

The present contribution addresses the effects of structural features of Pt NPs on the electrochemical performance in the hydrogen evolution reaction (HER). Our approach for the synthesis of metal NPs is distinct in that we produce a "monolayer" of spaced and defined Pt NPs directly on the electrode surface by controlled solid-state dewetting, i.e., by controlled heat-induced agglomeration of thin Pt films into particles [6,7] – see Fig. a. We use magnetron sputtering to deposit Pt films on electrically conductive substrates, followed by thermal treatment in a suitable environment. The resulting NP "monolayers" are tested for electrochemistry without using any binder or ionomer. By varying the duration of the thermal treatment systematically, we observe that dewetted Pt NPs show an evident increase of the ECSA area-specific HER activity compared to as-sputtered films – see Fig. b. This activity trend is consistent in the range of Pt particles’ size investigated (3-60 nm – see size control in Fig. c). The present contribution provides an analysis of the influence of NPs’ features, such as structure, grain size, grain boundaries’ density, and electronic metal-support interaction (EMSI), on the HER activity.

In a broader perspective, controlled dewetting allows to precisely tune the properties of metal NPs while at the same reduces the electrode complexity. Advantages are that single-crystalline, well-faceted NPs can be produced on desired electrically conductive substrates (see control of exposed facets in Fig. d). Moreover, dewetted NPs are free from impurities or additives, can be formed with desired composition by tuning the composition of the parent metal film, and can be formed on flat electrode geometries, which is ideal to minimize mass transport limitations and to enable accessibility for spectroscopic techniques.

[1] Zhu et al., Chem. Rev. 2020, 120 (2), 851.

[2] Lim et al., ACS Catal. 2021, 11 (12), 7568.

[3] de Gregorio et al., ACS Catal. 2020, 10 (9), 4854.

[4] Feng et al., J. Am. Chem. Soc. 2015, 137 (14), 4606.

[5] Zhu et al., Nano Research 2020 13:12 2020, 13 (12), 3310.

[6] Thompson, C.V., Annu. Rev. Mater. Res. 2012, 42, 399.

[7] Altomare et al., Chem. Sci. 2016, 7 (12), 6865.

Figure 1
How the Facet Edge Controls the Overall CO Oxidation in Nanoporous Gold: Combined Atomistic Characterization/DFT Study of Residual Ag Distribution and Catalytic Activity
Authors: Ayadathil Prajwal , Sandupatla Aditya , Chatterjee Abhijit
Published: February 2024

Nanoporous gold (NPG) formed via dealloying/selective dissolution of the Au−Ag alloy is known to be catalytically active toward CO oxidation reaction (COR) even at room temperature. The atomistically resolved NPG structure is obtained by simulating the dealloying of Au25Ag75 nanoparticles using a combination of kinetic Monte Carlo and molecular dynamics. The effect of adsorbed O is included. The experiment-like NPG structures from these computer simulations are characterized. We map the surface of NPG, determine the diverse binding sites, and assess their role in catalysing the COR. Local surface Ag composition, population density of undercoordinated Au/Ag atoms, and cluster size distribution of surface Ag atoms are measured. A high density of dislocation defects is found in the simulated structure. The rate-determining steps, namely, O2 binding and dissociation, are probed using density functional theory. We conclude that O2 binding/dissociation is facilitated at the facet edge. Residual Ag at the edge aids in the capture of O2. Subsequently, O2 dissociates after spilling over to Au sites at the facet edge. These conclusions are confirmed by showing that the normalized facet edge length of NPG and supported Au nanoparticles is linearly correlated to the experimental turnover frequency.

Keywords: nanoporous gold, dealloying, CO oxidation, elemental distribution, density functional theory, molecular dynamics, Monte Carlo

Figure : Dealloying of Au-Ag NP to get NPG which has high catalytic activity for COR

Figure 1
(Europe Section Heinz Gerischer Award) Endeavours in the Electro-Solar World of Schottky, Mott and Gerischer
Authors: Schmuki Patrik
Published: February 2024

The origins of semiconductor electrochemistry lies in the early 20th century with the pioneering work of scientists like Walter H. Schottky, Nevill Mott, and Heinz Gerischer. Schottky and Mott made significant contributions to the understanding of semiconductor physics, while Gerischer is often credited with laying the groundwork for the field of semiconductor electrochemistry. Particularly Gerischer's studies on the kinetics of electron transfer reactions at semiconductor-electrolyte interfaces have been fundamental to our understanding of semiconductor chemistry and photoelectrochemistry. His early work has conceptually created strong links between electrochemistry and solid state physics, has created a close connection to photochemistry, and has profoundly improved the understanding of interfacial reactions. It allowed to exploit the feature of semiconductors to conduct electricity under certain conditions and their conductivity being strongly altered by doping or by the application of an electric field or a photon flux.

These findings have stimulated a work in a wide range of science and led to the foundations towards tremendous success of applications across diverse fields such as Photovoltaics (Solar Cells), Photoelectrochemical Cells, Sensors, Catalysis, Batteries and Fuel Cells, Corrosion Protection, Electrochromic Devices or Water Treatment.

The presentation will give a personal perception of the principles, their use in the last 20 years. It is focused on TiO2 based semiconductor electrochemistry and its applications. It involves the growth and use of titania nanotubes their properties and applications, as well as – in recent years – the use of single atoms as co-catalysts in the field of semiconductor electrochemistry.
Charge Transfer-Induced Geometric Distortion in Ni(HCO3)2@CNT: Impact on Enhanced Catalytic Performance for Oxygen Evolution and Reduction Reactions
Authors: Jeong Jaeryeol , Lee Min Hyung
Published: February 2024

Multidimensional carbon isotopes, such as carbon nanotubes (CNTs) and graphene, have been extensively researched as intrinsic catalytic materials or hetero supports for catalytically active metal sites, owing to their high conductivity, thermal stability, and chemical inertness. However, the enhanced catalytic performance of most transition metal-based catalysts on carbon supports is considered to be primarily due to improved carrier transport kinetics resulting from the conductivity of carbon supports, although there may be other possible effects that are not yet well understood. In this presentation, we propose CNT-decorated Ni(HCO3)2 (denoted as Ni(HCO3)2@CNT) as a bifunctional catalyst for both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The sp3-like carbon in CNTs can induce charge transfer to the Ni active site within Ni(HCO3)2, which in turn induces strain in the Ni-O bond. This strain-induced Ni active site can stabilize the *O intermediate, leading to significantly lower potential barriers for the potential-determining steps of both OER and ORR compared to pristine Ni(HCO3)2. The adjustable catalytic activity enabled by interfacial charge transfer and its contribution to local structural distortion presents a straightforward approach to designing low-cost, highly efficient, and multifunctional catalysts for sustainable chemical energy conversion.
(Invited)The Role of the Catalyst Microenvironment in the Electrochemical Reduction of Carbon Monoxide
Authors: Endrődi Balázs , Kormanyos Attila , Drágity Deján , Galbicsek Noémi , Janaky Csaba
Published: February 2024

Carbon monoxide is already an important raw material for the synthesis of different bulk chemicals (e.g., phosgene and different products thereof). Considering that it can be a building block for the synthesis of virtually any organic compound, carbon monoxide might play an important role in the production of synthetic fuels and other typical petrochemical products. This can be performed under high temperature and pressure conditions in the Fischer-Tropsch process, but electrochemical methods also offer a possible way of forming different chemicals from carbon monoxide.

Because of the low solubility of carbon monoxide in water, instead of the routinely used H-cells, its reduction must be performed in gas-fed electrolyzer cells, ensuring a short diffusion length for the reactant. However, even in such devices the surface of the catalyst (nano)particles is typically surrounded by a thin water shell under operating conditions, caused by various effects such as electrowetting, or wetting by the formed products. The practical insolubility of carbon monoxide (that is ca. 30 times lower compared to the solubility of CO2) makes it vital to ensure that the thickness of this hydration layer is minimized, hence the reactant can reach the catalysts' surface in gas phase, meanwhile just enough amount of a proton source – water – is in the immediate vicinity.

The phase boundary between the catalyst particles, the liquid phase and the gas reactant can be engineered by using functional catalyst layer additives. Here we will demonstrate a commercial pore sealer for this purpose, ensuring the formation of C2+ products in CORR with high selectivity and rate.1 As no specific interaction between the polymer and the CO reactant was found, we assumed that the most important role of this polymer is to increase the hydrophobicity of the catalyst layer. To challenge this theory, various, systematically chosen polymeric materials were tested as catalyst binders to reveal any possible further contribution of certain motifs (e.g., functional groups, fluorinated backbone etc.), present in these polymers. The electrochemical results are contrasted with the detailed characterization of the structure, wetting and gas adsorption properties of the catalyst layer.

Reference

Kormányos, B. Endrődi, Z. Zhang, A. Samu, L. Mérai, G. F. Samu, L. Janovák, & C. Janáky (2023). EES Catalysis. https://doi.org/10.1039/D3EY00006K
(Keynote) Competition of Oxygen and Chlorine Evolution on Oxide Surfaces – a Soft X-Ray and Dems Approach to Identification of Active Site
Authors: Krtil Petr , Minhova Macounova Katerina , Astudillo Catalina , Sakata Kaoruho , Amemiya Kenta
Published: February 2024

Anodic gas evolving reactions, e.g. oxygen evolution and chlorine evolution, are of fundamental importance both in energy storage as well as in electrolytic production of chemicals. Both reactions are of electrocatalytic nature, proceed in the same potential range and are catalyzed by the same types of electrode materials. While the oxygen evolution is thermodynamically favored the two electron chlorine evolution is kinetically preferred, namely at acid and neutral pH. This kinetic preference is industrially explored in chlor-alkali processes as well in chlorate electrolysis. The growing interest in electrolytic hydrogen production fueled by the popularity of the hydrogen as the likely replacement of fossil fuels brings up the question of the tolerance of the industrial anodes to presence of chlorides in the water intended for electrolytic hydrogen production. Such a tolerance can be best achieved by steering the selectivity of the anode between oxygen and chlorine evolution aiming eventually at the possibility of the sea water use in hydrogen producing water electrolysis. So far existing attempts at control the anode selectivity in presence of chlorides explore two principal approaches – pH control and surface engineering. While the pH related approach is rationalized by different pH sensitivity of each of the competing reaction the surface engineering related activities so far rely on trial and error approach. Qualitatively the selectivity may be controlled by either selectively promoting/suppressing each of the contributing reactions. While the literature lists attempts when the overall selectivity towards OER is apparently achieved by selective suppression of CER [1] more recent reports suggest that the actual selectivity is in fact controlled by the ability of the catalysts to support a lattice oxygen activating mechanism of the oxygen evolution process [2]. While these assignments are based on correlation of selectivity measurements with local structure and DFT modelling and a direct evidence of such a behavior is so far missing. This paper will document here the capability of the real-time and operando soft X-ray absorption spectroscopy [3] to provide this missing evidence. Anodic behavior of two type of ruthenium oxide electrodes in chloride free and chloride containing solutions will be documented by comparison of the nature and potential dependent population of the oxygen related intermediates formed at anode surface in the potential range of oxygen and chlorine evolution in acid media (pH=1) and combined with DEMS data to identify the active sites for each contributing electrode reaction.

References:

V Petrykin, K Macounova, O.A Shlyakhtin, P. Krtil, Angew. Chem., 122, 4923-4925

K. Minhová Macounová, R. K. Pittkowski, R. Nebel, A. Zitolo, P. Krtil, Electrochim. Acta, 427, 140878

K. Amemiya, K. Sakata, M. Suzuki-Sakamaki, Rev. Sci. Instrum. 91, 093104
(Invited) Tuning the Activity of Iron Phosphide Electrocatalysts for Sustainable Energy Conversion
Authors: Emin Saim , Chouki Takwa , Machreki Manel , Stefanov Plamen , Rutkowska Iwona A. , Rytelewska Beata , Kulesza Pawel , Tyuliev Georgi , Harb Moussab , Azofra Luis
Published: February 2024

Electrocatalysis is a promising approach for the sustainable conversion of renewable energy sources, such as solar and wind power, into chemical energy that can be stored and used on demand. By harnessing renewable electricity to drive electrochemical reactions, we can produce fuels and chemicals in a way that is both clean and cost-effective. As we continue to develop new electrocatalytic materials and improve the efficiency of existing processes, the potential for electrocatalysis to transform our energy system will only continue to grow.

We report the use of iron phosphide (Fe2P, FeP) in several electrocatalytic applications, such as reduction of nitrate ions (NO3), hydrogen and oxygen evolution studies. The electrochemical reduction of the nitrate ion (NO3), a widespread water pollutant, to valuable ammonia (NH3) is a promising approach to achieving green energy conservation. Particularly, FeP and Fe2P phases were successfully demonstrated as efficient catalysts for NH3 generation. Detection of the in-situ formed product using a bi-potentiostat was achieved by electrooxidation of NH3 to nitrogen (N2) on a Pt electrode. The Fe2P catalyst exhibits the highest Faradaic efficiency (96%) for NH3 generation with a yield (0.25 mmol h−1 cm-−2 or 2.10 mg h−1 cm−2) at −0.55 V vs. reversible hydrogen electrode (RHE). To get relevant information about the reaction mechanisms and the fundamental origins behind the better performance of Fe2P, density functional theory (DFT) calculations were performed.

In addition to NH3 synthesis, the iron phosphide catalyst was used in electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) studies. To enhance the catalytic activities of the obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures. Heat-treatment at 500°C under a reductive atmosphere induced structural changes in the samples: (i) Fe2P yielded a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities of heat-treated Fe3P−500°C, and Fe2P/FeP−500°C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M H2SO4. The lowest HER electrode potential of 110 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2 was achieved with a Fe2P/FeP−500°C catalyst. The intrinsic activity of FeP catalysts was also tuned and studied for OER.
(Invited) High Yield and Selective Electrocatalytic Reduction of Nitroarenes via Polyoxometalate Redox-Mediated Chronoamperometry
Authors: Broadhurst Daniel Harry , Symes Mark
Published: February 2024

Anilines are major commodity chemicals used extensively in the production of pharmaceuticals, dyes, and polymers. However, the typical methods for synthesizing anilines suffer from poor environmental sustainability. Here, we report an electrocatalytic route for the production of anilines that works in aqueous solution at room temperature and pressure, where the electrons and protons required to reduce the nitrobenzene precursors are obtained from water. Excellent selectivities are obtained for a range of anilines, including species with ortho-iodides that are very challenging to obtain by other methods. Our approach relies on the use of a polyoxometalate redox mediator that shuts off the direct electro-reduction of the nitrobenzene at the electrode surface and thus prevents unproductive side reactions. Given the scale and current environmental impact of global aniline production, this electrochemical route holds promise for the development of more sustainable processes for the production of these vital chemical feedstocks.

Figure 1
Nicop Anchored Porous Ti3C2tx Support with 3D Interconnected Structure for Advanced Hydrogen Evolution Reaction Electrocatalysts
Authors: Kim Minjun , Yoo Pil Jin
Published: February 2024

MXene have gained much attention as promising electrocatalysts for noble metal-free hydrogen evolutrion reaction (HER) electrocatalysts owing to their high electrical conductivity, hydrophilic surfaces, abundant functional groups, and rational design for hybridization with other materials. In this study, a novel porous monolayered-Ti3C2TX@NiCoP (P-Ti3C2Tx@NiCoP) nanostructure was developed with 3D interconnected structure to significantly improve charge transfer capability and electrocatalytic activity. A strategic approach of modifying pristine Ti3C2Tx monolayers and combining them with other active cocatalysts. Specifically, the H2O2-utilized oxidation and HF etching process formed a highly microporous structure with a maximized surface area of monolayered MXenes as the support. A subsequent solvothermal process followed by phosphidation enabled successful anchoring of highly HER-active NiCoP nanoclusters onto abundantly exposed terminal edges of the P-Ti3C2Tx support. The structural porosity of the P-Ti3C2Tx nanoflakes played an important role in creating additional room for embedding catalytically active species while stably imparting high electrical conductivity to accelerate charge transfer to NiCoP nanoclusters. Moreover, inspired by the pH dependent change of structural arrangement of the Ti3C2Tx, we successfully induced 3D-interconnetecd structure by modulating surface electrostatic forces among Ti3C2Tx monolayers. Of note, the 3D-interconnected structure would shift charge transfer behavior from intermolecular to intramolecular aspects and this would contribute to enhanced charge transfer kinetics. With structural modification of support material and effective hybridization of active species, P-Ti3C2Tx@NiCoP showed highly enhanced HER activity with significantly lower overpoential of 115 and 101 mV at a current density of -10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively, along with showing long-term stability over 60 h. As such, our approach of designing structurally modified-Ti3C2Tx and hybridization with other electrocatalytically active species would function as a solid platform for implementing Ti3C2Tx-based hetero-nanostructures to achieve state-of-the-art performance in next-generation energy conversion applications.
Investigation of Pd Based Metal-Carbon As Bifunctional Electrocatalyst for OER and ORR
Authors: Vashishth Surishi , Eswaramoorthy Muthusamy
Published: February 2024

Developing oxygen reduction/ evolution reaction (ORR/OER) bifunctional electrocatalysts has great significance for promoting the sustainable energy conversion. Herein, Pd (5wt% only) based bimetallic catalyst adhered well on heteroatom doped conducting carbon substrate is designed and constructed. Rich defects, multiple active centers and strong synergistic effect with rapid ion/electron transport ability allow the electrocatalyst to exhibit superior performance (Li et al., 2019). Owing to its more active metal-Pd sites due to high surface area conducting carbon matrix an ultralow overpotential of 240 mV at 10 mA/cm2 for OER was obtained. It outperforms state of art RuO2 and Pt/C electrocatalyst. High half-wave potential (E1/2) of 0.821 V for ORR is comparable to commercial Pt/C (E1/2 =0.819 V) electrocatalysts was attained. The catalyst exhibits a prolonged stability in alkaline medium at 20 mA cm-2 for 24 h for OER and a small 20 mV shift in linear sweep voltammetry scan after accelerated durability test for 5000 cycles at 50mV/s for ORR. In-situ Raman analysis exhibits surface oxidation of electrocatalyst on OER in highly alkaline (1M KOH) conditions.

Reference:

Li, S., Hao, X., Abudula, A., & Guan, G. (2019). Nanostructured Co-based bifunctional electrocatalysts for energy conversion and storage: current status and perspectives. Journal of Materials Chemistry A, 7(32), 18674–18707. https://doi.org/10.1039/C9TA04949E
Metal-Oxygen Covalency Competition of Unsymmetrical Metal Pairs for Enhanced Bifunctional Oxygen Electrocatalysis
Authors: Zhou Tao , Guo Zheng Xiao
Published: February 2024

Rechargeable zinc-air batteries are considered promising energy conversion devices due to their inherent safety and high energy-to-cost ratio. However, the sluggish kinetics of oxygen evolution reaction and oxygen reduction reaction during the charging-discharging process lead to low round trip efficiency and power density. The synthesis of efficient and stable bifunctional oxygen electrocatalysts constitutes the bottleneck to construct applicable ZABs.

Here, we report an Mn-doped ruthenium oxide electrocatalyst that exhibits remarkable ORR/OER activity, with a low potential gap of 0.62V between the half-wave potential of ORR and the OER potential at 10mA cm-2. The Mn-RuO2 assembled ZABs present a high power density of 179 mW cm-2 and long lifespans of 800 h. Metal covalency competition induces surface Mn atoms shows more favorable adsorption behavior for ORR and Ru atoms shows more favorable adsorption behavior for OER. The charge redistribution between asymmetrical Ru-O-Mn pairs results in dual actives sites towards OER/ORR. The surface ruthenium stabilizes the O* intermediate due to the weaker hybridization of the lattice Ru-O bond. The upshift of the dz2 orbital relieves the over-binding of the critical intermediates OH* on the Mn atom. Such dual Ru-Mn sites minimized the OER/ORR activity gap restricted by scaling relationships. Our findings rationalize the double active sites mechanism in Mn-RuO2 electrocatalyst and provide a strategy to enhance bifunctional catalytic performance.

Figure 1
Unraveling the Crystal Facet and Support Effects on the Oxygen Evolution Activity of Cobalt Oxide Using Single Nanoparticle Electrocatalysis
Authors: Amin Hatem M.A. , Liu Zhibin , Peng Yuman , Corva Manuel , Hosseini Yazdeli Seyed Pouya , Pentcheva Rossitza , Tschulik Kristina
Published: February 2024

Transition metal oxide catalysts have recently gained special interest in alkaline water electrolysis due to their relatively high abundancy and high catalytic activity. However, their catalytic performance has typically been evaluated based on measurements at composite electrodes, that is by immobilizing a large number of these nanoparticles together with inactive binders and additives on a current collector/support and measuring only their integral activity. In such studies, it is challenging to deconvolute the catalyst intrinsic properties from matrix effects. For example, the measured catalytic trends can be influenced by blocking of catalyst active sites by the additives or by non-optimal iR compensation or by different porosity within the composite, impeding a direct comparison of nanocatalysts.[1] Alternatively, single-particle electrocatalysis by the “nano impact” approach has been applied to assess the intrinsic activity of nanoparticles (NPs) at the individual particle level.[2] Exploiting this method, we demonstrate how the catalyst’s crystal facet/shape influences the OER activity by comparing the activity of cubes and spheres of Co3O4.[3] In contrast to the tentative differences in OER activity recorded on ensembles, the single particle studies unambiguously reveal that Co3O4 cubes are more active than spheres when both NPs have otherwise identical parameters. We also can link our experimental data to theory data obtained from DTU+U calculations. Furthermore, we investigate catalyst-support effects and show the higher activity of Pt support than carbon.[4]. This approach enables the identification of highly active facets to guide shape-selective syntheses of improved metal oxide nanocatalysts for water oxidation.

References

[1] N. Blanc, C. Rurainsky, K. Tschulik, J. Electroanal. Chem. 872(2020)114345

[2] A. El Arrassi, Z. Liu, M. V. Evers, N. Blanc, G. Bendt, S. Saddeler, D. Tetzlaff, D. Pohl, C. Damm, S. Schulz, K. Tschulik, J. Am. Chem. Soc. 141 (2019) 9197

[3] Z. Liu, H. M.A. Amin, Y. Peng, M. Corva, R. Pentcheva, K. Tschulik, Adv. Funct. Mater. 33 (2023) 2210945

[4] Z. Liu, M. Corva, H.M.A. Amin, N. Blanc, J. Linnemann, K. Tschulik, Int. J. Mol. Sci. 22 (2021)13137.

Figure: Single particle electrochemistry illustrating the higher OER activity of Co3O4 cubes than spheres.

Figure 1
LiPON/Multilayer-Graphene Interface Enables High-Rate Charging and Discharging
Authors: Yamamoto Satoshi , Sakakibara Ryotaro , Motoyama Munekazu , Ishigaki Norikazu , Norimatsu Wataru , Iriyama Yasutoshi
Published: February 2024

Graphite is the anode-active material commonly used in LIBs. In LIB, solid electrolyte interphase (SEI) is formed by the reduction of the liquid electrolyte, and the SEI plays a role as a passive film. In the charging process, Li ions transport in the liquid electrolyte and SEI, desolvation reactions of Li ions occur, and then Li ions insert into the graphite anode. It has been reported that the desolvation reaction of Li ions is the rate-limiting process[1].

Lithium phosphorous oxynitride glass (LiPON) is a well-known material as a solid electrolyte. However, it has been reported that the electrochemical window of LiPON ranges from 0.68 V to 2.63 V[2]. Therefore, it is possible that the decomposition reaction of LiPON occurs when the electrochemical cell is charged. Since the decomposition products can be a resistance, LiPON that is not easily reduced is required.

In this study, we focused on the lithium phosphorus oxynitride glass (LiPON) electrolyte/multilayered graphene (MGr) film interface as an example without the desolvation process. In addition, we have investigated the relationship between LiPON composition ratio, electronic properties, and interfacial resistance by changing the sputtering conditions for LiPON film. Consequently, we found that the charge-transfer resistance at the MGr/LiPON interface was significantly small, although the MGr/LiPON interface was supposed to have inorganic solid electrolyte interphase resulting from the LiPON reduction decomposition. The figure shows a schematic illustration of the Liquid Electrolyte/MGr interface and the LiPON/MGr interface.

Figure 1
Stepwise Optimization of Single-Ion Conducting Polymer Electrolytes for High-Performance Lithium-Metal Batteries
Authors: Dong Xu , Chen Zhen , Gao Xinpei , Mayer Alexander , Liang Hai-Peng , Passerini Stefano , Bresser Dominic
Published: February 2024

Single-ion conducting polymer electrolytes (SIPEs) are among the most promising candidates for high-energy and high-safety lithium-metal batteries. Nevertheless, their commonly limited ionic conductivity and electrochemical stability hamper their practical application. Herein, three new SIPEs, i.e., poly (1,4-phenylene ether ether sulfone)-Li, polysulfone-Li, and hexafluoropolysulfone-Li, all comprising covalently tethered perfluorinated ionic side chains, were designed, synthesized, and comparatively investigated to unveil the influence of the backbone chemistry and the concentration of the ionic group on their electrochemical properties and the eventual cell performance. In particular, the trifluoromethyl group in the backbone and the concentration of the ionic group turn out to play an important role for the charge transport and electrochemical stability towards oxidation. As a result, the combination of both leads to the best-performing SIPE with a high ionic conductivity of ca. 2.5 × 10-4 S cm-1, an anodic stability of >4.8 V, and the best cycling stability in Li‖LiNi0.6Co0.2Mn0.2O2 cells.
(Poster Award Winner 1) Investigating the Impact of Ethylene Carbonate Reaction Pathways on the Solid Electrolyte Interphase in Li-Ion Batteries
Authors: Lundström Robin , Gogoi Neeha , Hou Xu , Berg Erik J.
Published: February 2024

A high-performing Li-ion battery relies heavily on the solid electrolyte interphase (SEI), which is composed of various decomposition products, primarily from reduced additives or electrolyte species such as ethylene carbonate (EC). The composition of the SEI evolves and continues to form during the operation of a Li-ion battery, making it challenging to fully understand through post-mortem analysis alone. To gain a complete understanding of the EC reaction pathways and their respective contributions to the SEI, it is necessary to employ analytical techniques that monitor the battery during operation. Online Electrochemical Mass Spectrometry (OEMS) is one such technique that can sample the gas composition of a battery, providing an overview of voltage-dependent gas evolution processes.1

This presentation focuses on two EC reaction pathways that occur on a model carbon electrode.2 The first pathway, the "EC ring-opening" reaction pathway, is initiated by hydroxides/alkoxides at potentials above 1.5 V vs. Li+/Li and is associated with CO2 evolution.3
,
4 The second pathway, the "EC reduction" pathway, occurs at potentials below 0.9 V vs. Li+/Li and is identified by C2H4 evolution.5 Both reaction pathways contribute to the formation of the SEI, and they compete with each other. If EC ring-opening is favoured, it can suppress EC reduction. Figure 1 illustrates the competing relationship between the two different EC reaction pathways, where the addition of EC ring-opening initiators (H2O) increases CO2 and reduces C2H4. It is essential to consider all possible EC reaction pathways, not just the desired one, when forming the SEI. The presentation concludes with a discussion of the potential implications that EC ring-opening may have on a Li-ion cell.

Figure 1
. Comparison between the total CO2 and C2H4 evolution during the initial cyclic voltammetry cathodic sweep in a Glassy carbon | 1 M LiPF6 EC:DEC | LiFePO4 cell.

References

R. Lundström and E. J. Berg, J. Power Sources, 485, 229347 (2021).

R. Lundström, N. Gogoi, X. Hou, and Berg Erik J., Submitted (2023).

M. Metzger, B. Strehle, S. Solchenbach, and H. A. Gasteiger, J. Electrochem. Soc., 163, 1219–1225 (2016).

L. Gireaud, S. Grugeon, S. Laruelle, S. Pilard, and J.-M. Tarascon, J. Electrochem. Soc., 152, A850 (2005).

R. Imhof and P. Novák, J. Electrochem. Soc., 145, 1081–1087 (1998).

Figure 1
Stabilizing of Lithium-Solid-Electrolyte Interfaces by Atomic Layer Deposition Prepared Nano-Interlayers for a Model All-Solid-State Battery
Authors: Götz Rainer , Ahaliabadeh Zahra , Llanos Princess Stephanie , Bandarenka Aliaksandr S. , Kallio Tanja
Published: February 2024

To understand the electrochemistry of all-solid-state batteries (ASSBs), the use of electrochemical equivalent circuits with a physical meaning is essential. A model battery is needed whose characterization is independent of the influence of the complex battery assembly.

Therefore, LICGC©, a model solid electrolyte is chosen that shows stability in air, but on the other hand is also well-known for its instability against metallic lithium upon direct contact. As a first step towards a model ASSB, the interface between lithium and the solid electrolyte (SE) is stabilized with thin (5 nm and 10 nm) coatings of titanium oxide (TO). Impedance data shows that symmetric cells with the TO coatings are protected from rapid SE surface degradation due to reducing lithium. Titanium oxide nano-interlayers can hence serve as a protective interlayer on the anode side of a model ASSB. Additionally, the formation of space charge layers (SCLs), which have been already documented for LICGC alone, appear once again at the interface between metal oxide interlayer and the solid electrolyte. The observed SCL thickness can reach up to ∼ 5 µm (cf. figure).

Figure 1
(Invited) Combining Constant Potential Molecular Dynamics and Experiments to Study Electrolyte Effects at Solid/Liquid Interfaces
Authors: Serva Alessandra , Salanne Mathieu
Published: February 2024

Liquid electrolytes are at the heart of many devices in energy storage and conversion applications. Bringing an atomistic picture of the composition-properties relation is essential to understand how their reactivity can be tuned, both in the bulk and at interfaces, by variation of their composition.

In this talk, I will present some recent works where we elucidated the role of the electrolyte, by using state-of-the-art constant potential classical Molecular Dynamics [1] in combination with experiments. I will first introduce some developments that we did for treating metallic surfaces within the constant potential approach, which allows computing interfacial properties, e.g. capacitance, in good agreement with experiments.[2] Then, I will show a study about the insertion process of Li+ into LiFePO4 and K+ into Prussian blue for Li-ion and K-ion batteries, in aqueous vs non-aqueous electrolytes. I will describe the molecular aspects of the electrode-electrolyte interface that dictate ion transport and insertion processes, which strongly depend on the nature of the electrolyte.[3]

I will finally illustrate some exciting perspectives for the design of more complex electrolytes, where water and an organic solvent are mixed, to control the reactivity of water at a solid/liquid interface. This finds direct applications in practical devices such as Li-ion batteries, multivalent batteries, or even electrolyzers. Our strategy was to confine the reactive species, i.e. water, in a non-reactive organic matrix and different salts. Modifying the nature of the salt as well as the salt/water ratio can be used to fine tune the water reactivity at the interface by controlling its coordination environment at both short- and long-range.[4,5]

References

[1] A. Marin-Laflèche et al., J. Open Source Softw., 5, 2373, 2020.

[2] A. Serva, L. Scalfi, B. Rotenberg, M. Salanne, J. Chem. Phys., 155, 044703, 2021.

[3] P. Lemaire, A. Serva et al., ACS Appl. Mater. Interfaces, 14, 20835, 2022.

[4] N. Dubouis, A. Serva et al., Nat. Catal., 3, 656, 2020.

[5] A. Serva, N. Dubuois, A. Grimaud, M. Salanne, Acc. Chem. Res., 54, 1034, 2021.