Oxygen Evolution Catalysis Research Articles

Engineering Lattice Oxygen Regeneration of NiFe Layered Double Hydroxide Enhances Oxygen Evolution Catalysis Durability.

The lattice oxygen mechanism (LOM) endows NiFe layered double hydroxide (NiFe-LDH) with superior oxygen evolution reaction (OER) activity, yet the frequent evolution and sluggish regeneration of lattice oxygen intensify the dissolution of active species. Herein, we overcome this challenge by constructing the NiFe hydroxide/Ni4Mo alloy (NiFe-LDH/Ni4Mo) heterojunction electrocatalyst, featuring the Ni4Mo alloy as the oxygen pump to provide oxygenous intermediates and electrons for NiFe-LDH. The released lattice oxygen can be timely offset by the oxygenous species during the LOM process, balancing the regeneration of lattice oxygen and assuring the enhancement of the durability. In consequence, the durability of NiFe-LDH is significantly enhanced after the modification of Ni4Mo with an impressively durability for over 60 h, much longer than that of NiFe-LDH counterpart with only 10 h. In-situ spectra and first-principle simulations reveal that the adsorption of OH- is significantly strengthened owing to the introduction of Ni4Mo, ensuring the rapid regeneration of lattice oxygen. Moreover, NiFe-LDH/Ni4Mo-based anion exchange membrane water electrolyzer (AEMWE) presents an impressive durability for over 150 h at 100 mA cm-2. The oxygen pump strategy opens opportunities to balance the evolution and regeneration of lattice oxygen, enhancing the durability of efficient OER catalysts.

Engineering Lattice Oxygen Regeneration of NiFe Layered Double Hydroxide Enhances Oxygen Evolution Catalysis Durability

The lattice oxygen mechanism (LOM) endows NiFe layered double hydroxide (NiFe‐LDH) with superior oxygen evolution reaction (OER) activity, yet the frequent evolution and sluggish regeneration of lattice oxygen intensify the dissolution of active species. Herein, we overcome this challenge by constructing the NiFe hydroxide/Ni4Mo alloy (NiFe‐LDH/Ni4Mo) heterojunction electrocatalyst, featuring the Ni4Mo alloy as the oxygen pump to provide oxygenous intermediates and electrons for NiFe‐LDH. The released lattice oxygen can be timely offset by the oxygenous species during the LOM process, balancing the regeneration of lattice oxygen and assuring the enhancement of the durability. In consequence, the durability of NiFe‐LDH is significantly enhanced after the modification of Ni4Mo with an impressively durability for over 60 h, much longer than that of NiFe‐LDH counterpart with only 10 h. In‐situ spectra and first‐principle simulations reveal that the adsorption of OH− is significantly strengthened owing to the introduction of Ni4Mo, ensuring the rapid regeneration of lattice oxygen. Moreover, NiFe‐LDH/Ni4Mo‐based anion exchange membrane water electrolyzer (AEMWE) presents an impressive durability for over 150 h at 100 mA cm−2. The oxygen pump strategy opens opportunities to balance the evolution and regeneration of lattice oxygen, enhancing the durability of efficient OER catalysts.

Stabilization of High‐Valent Molecular Cobalt Sites through Oxidized Phosphorus in Reduced Graphene Oxide for Enhanced Oxygen Evolution Catalysis

Stabilization of High‐Valent Molecular Cobalt Sites through Oxidized Phosphorus in Reduced Graphene Oxide for Enhanced Oxygen Evolution Catalysis

Stabilization of High-Valent Molecular Cobalt Sites through Oxidized Phosphorus in Reduced Graphene Oxide for Enhanced Oxygen Evolution Catalysis.

Heterogeneous molecular cobalt (Co) sites represent one type of classical catalytic sites for electrochemical oxygen evolution reaction (OER) in alkaline solutions. There are dynamic equilibriums between Co2+, Co3+ and Co4+ states coupling with OH-/H+ interaction before and during the OER event. Since the emergence of Co2+ sites is detrimental to the OER cycle, the stabilization of high-valent Co sites to shift away from the equilibrium becomes critical and is proposed as a new strategy to enhance OER. Herein, phosphorus (P) atoms were doped into reduced graphene oxide to link molecular Co2+ acetylacetonate toward synthesizing a novel heterogeneous molecular catalyst. By increasing the oxidation states of P heteroatoms, the linked Co sites were spontaneously oxidized from 2+ to 3+ states in a KOH solution through OH- ions coupling at an open circuit condition. With excluding the Co2+ sites, the as-derived Co sites with 3+ initial states exhibited intrinsically high OER activity, validating the effectiveness of the strategy of stabilizing high valence Co sites.

MnO2/rGO bifunctional catalyst and support materials for gel polymer electrolyte based Zn-air batteries

A high-performance and long-lasting, rechargeable Zn-air battery requires a reliable and effective bifunctional catalyst material to facilitate the oxygen reduction and oxygen evolution reactions during the battery operation. Manganese oxide (MnO2) is a promising non-precious perspective due to its multivalency and various polymorphic structures that effectively catalyze oxygen evolution and reduction. In the present work, MnO2 nanowires (NWs) have been integrated with over-reduced graphene oxide (rGO) in various concentrations via a facile hydrothermal route. The synthesized materials, tested in lab-made zinc-air battery devices fabricated using gel polymer electrolyte, exhibit a significant enhancement in the performance and 2–3 times the cycle life compared to the bare MnO2. The ZAB device was tested for galvanostatic charge-discharge technique, and results exhibit a cycle life of 165 h (495 cycles@20 min per cycle) when discharged up to 1.0 V at a current density of 5.2 mA/cm2 and displayed a capacity of 731 mAh/gZn. Reduced graphene oxide acts as a support material that enhances the conductivity and surface area of the active material and also provides active sites for catalysis. This work signifies the importance of the engineering of the catalyst, support material, and additives, as slight changes may result in a significant enhancement in the cycle life.The appropriate composition of catalyst and support material and a compatible gel polymer electrolyte facilitates the fabrication of flexible zinc-air batteries for various applications.

Rutile-structured high-entropy oxyfluorides: A platform for oxygen evolution catalysis

High-entropy (HE) design provides ample opportunities for accessing catalysts with unique physiochemical properties for advanced energy and environmental applications. Although a variety of multi-cationic high-entropy materials (HEMs) have been identified, HEMs consisted of multiple cationic and anionic elements are still limited. Herein, we present the design and synthesis of a series of rutile-structured high-entropy oxyfluorides (HEOFs), including [RuO2]x[MgMnZnCoF2]y, [MnO2]x[MgMnZnCoF2]y, [MoO2]x[MgMnZnCoF2]y, [SnO2]x[MgMnZnCoF2]y and [TiO2]x[MgMnZnCoF2]y (x:y = 3:1, 2:1, 1:1). All the HEOFs are obtained through mechanochemical alloying rutile-structured oxide and fluoride precursors and the HEOFs inherit the crystal structures of the skeleton oxides. Moreover, the HEOFs exhibit enhanced electrocatalytic oxygen evolution reaction (OER) activity than the corresponding one-element precursors. Typically, the best-performed HEOF [RuO2]3[MgMnZnCoF2]1 catalyst requires an overpotential of 240 mV to achieve a current density of 10 mA cm−2, which is lower than RuO2 (291 mV). More impressively, the specific mass activity of [RuO2]3[MgMnZnCoF2]1 is 537.1 A gRu−1 at 1.55 V (vs RHE), which is ca. 7.6 times that of RuO2 (70.5 A gRu−1). The enhanced electrocatalytic OER performance obtained on [RuO2]3[MgMnZnCoF2]1 is ascribed to the contribution of the different cationic and anionic elements that modulates the electronic structures of the pristine RuO2, which facilitates efficient OER kinetics. This work demonstrates the efficacy of high-entropy design towards approaching excellent catalysts for enhanced electrocatalysis.

The mechanisms of the copper-carbonate catalyzed oxygen evolution reaction

Copper carbonate/bicarbonate complexes are good catalysts of the oxygen evolution reaction, OER. Previous electro-catalytic studies suggested that at pH 10.8 the active intermediate is a CuIII complex whereas at pH 6.8 the active intermediate is a CuIV complex. Previous pulse-radiolysis studies indicated that CuIII complexes are the active intermediates at both pHs. To solve the source of this discrepancy, the copper carbonate/bicarbonate catalyzed OER using peroxy-mono-sulfate as the oxidant was studied. In this system CuIV complexes are the active intermediates. The result points out that two electron oxidants yield CuIV complexes and one electron oxidants yield CuIII complexes; both types of complexes are water oxidation agents. Electrochemical processes might proceed via both mechanisms as the anode can act as a two-electron acceptor. Thus, pulse-radiolysis does not always yield the same intermediates as electrochemistry.

Manganese doped tailored cobalt sulfide as an accelerated catalyst for oxygen evolution reaction

Developing an efficient, robust, and noble metal-free electrocatalyst that can catalyse oxygen evolution reactions (OER) remains a significant challenge. CoS2, a representative of pyrite form transition metal dichalcogenides, has recently been identified as an economical catalyst. Here, an incredibly quick and scalable technique for novel catalysts synthesized with the use of the microwave method was introduced. Manganese-doped cobalt sulphide (Mn-CoS2) showed outstanding OER with a very low overpotential of 227 mV at 10 mA cm−2. Exposure of surface atoms resulted in high electrochemical activity, where the defects facilitated charge and mass transfer along the nanostructure, allowing surface dependent electrochemical reactions to be performed more efficiently. The electronic properties of pristine and transition-metal-doped CoS2 structures were also investigated using density functional theory (DFT). To better understand transition metal’s dependent impact on crystal structure, orbital electronic participation, charge density, and charge transformation in both pristine and Mn-dopedCoS2 frameworks were calculated and analysized. Our synthesis approach is primarily commercial and extensible, overcoming synthesis challenge of transition metal sulphide nanostructures with prime quality and implying a potential for commercial uses.

Vanadium-doped FeO/NiS nanosheet arrays: Synergistic heterometal doping and heterostructure design for enhanced oxygen evolution catalysis

The quest for high-performance OER electrocatalysts has been a focal point in the field of energy conversion and storage. Despite the promise shown by nickel sulfide-based materials, the enhancement of their catalytic activity through singular strategies has been found to be inadequate for achieving the desired comprehensive performance improvements. In this context, we introduce a novel V-doped FeO/NiS nanosheet array (V-FeO/NiS/NF) synthesized through a synergistic approach involving heteroatom doping and heterostructure engineering. This advanced material exhibits structural integrity, a three-dimensional nanosheet morphology, and superior electrical conductivity, which collectively contribute to its exceptional electrochemical performance. The V-FeO/NiS/NF electrode can reach a current density of 10 mA cm−2 with an impressively low overpotential of 213 mV and sustains its activity for an extended period of 196 hours, surpassing the stability and efficiency of many electrodes. Theoretical insights reveal that vanadium doping significantly lowers the adsorption free energy of key reaction intermediates, thereby facilitating the OER process. This study not only presents a robust and efficient OER electrocatalyst but also paves the way for the design of advanced, cost-effective nickel-based sulfide catalysts through strategic heteroatom incorporation and structural optimization.

Probing intermediate configurations of oxygen evolution catalysis across the light spectrum

Probing intermediate configurations of oxygen evolution catalysis across the light spectrum

Construction of iron-doped nickel cobalt phosphide nanoparticles via solvothermal phosphidization and their application in alkaline oxygen evolution

Multi-metallic phosphides offer the possibility to combine the strategies of surface reconstruction, electronic interaction and mechanistic pathway tuning to achieve high electrocatalytic oxygen evolution activity. Here, iron-doped nickel cobalt phosphide nanoparticles (FexCoyNi2-x-yP) with the crystalline NiCoP phase are for the first time synthesized by the solvothermal phosphidization method via the reaction between metal–organic frameworks and white phosphorus. When used to electrochemically catalyze oxygen evolution reaction (OER), the Fe0.4Co0.8Ni0.8P supported by nickel foam requires only 248 mV overpotential to achieve 10 mA cm−2 current densities, and is robust towards the long-term OER in 1 M KOH. The higher number of electrochemically active sites can account for the good OER activity, along with the improved intrinsic activity which is caused by the electron interaction that optimizes the adsorption energy of hydroxyl intermediates, and that increases the acidity of high-valent metal centers. The OER mechanistic pathway involves both adsorbate and lattice oxygen. Surface conversion is observed after OER in alkaline solution, and metal phosphide layer transforms to metal oxides and (oxy)hydroxides.

Synergistic Electrocatalysts Impact Efficient and Durable Oxygen Evolution Catalysis for Proton Exchange Membrane Water Splitting

Low-temperature water electrolysis can rapidly produce environmentally sustainable or green hydrogen, and is a prospective means of storing energy from renewable but intermittent power sources, such as wind and solar, in future clean energy infrastructure (1-4). Commercial water electrolysis either use liquid alkaline electrolyte or proton exchange membrane electrolyte (1). The proton exchange membrane water electrolysis (PEMWE) offers more advantages than the alkaline counterpart, such as higher purity of H2, lower resistance losses, more compact design, and what the most important is the compatible with the intermittent of the renewable energy (1-2). The grant challenge remaining in PEMWE is the development of the highly active, cost effective and stable catalysts for oxygen evolution reaction (OER), which is very sluggish requiring large amounts of precious metal as the catalysts, such as Ir, Ru and their oxides (1).In PEM water electrolysis cells, the catalysts should have high surface areas and high porosities that exposit sufficient active sites available to the reactants and electrolyte, as well as transferring the bubble out of the catalyst surface to ensure a fast mass transfer (5). Also, the OER is dependent on the inherent conductivity of the catalysts or the supports (1). For example, poor electronic conductivity within the catalyst layer will result in poor lateral conductivity across the catalyst layer, thus catalyst not in the vicinity of the porous transport layer will not participate in the reaction. To enable the widespread penetration of the PEMWE technologies, it is urgently to reduce the Ir loading to the sustainable level (~ 0.3 mg/cm2) compared with the current commercial usage (2-6 mg/cm2). Alternatively, to develop precious metal free catalyst with high efficiency and sustained durability (5).In this presentation, we will describe a method of preparing highly active yet stable synergistic electrocatalysts for oxygen evolution reaction for PEMWE. The new catalysts contain IrCoOx/ RuCoOx cluster and La&Li co-doped Co3O4 fiber which was derived from cobalt zeolitic imidazolate framework as precursor. The OER activities of the catalysts were first tested in O2 saturated acidic electrolyte by ring disk electrode (RDE), which displayed high mass activity 26-50 times that of commercial Ir and RuO2. The catalysts were fabricated into membrane electrode assemble and measured under real PEM water electrolysis condition. The cells demonstrated 2 A/cm2@1.76 V @0.25 ± 0.05 mgIr/cm2 loading, and negligible degradation after ~250 h chronoamperometric measurements at 2 A/cm2 (6), which meets the target set by US DOE for OER catalysts for PEMWE.The characterizations of the fresh and post-electrochemical samples were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), transmission electron microscopy (TEM), Raman spectroscopy and BET surface analysis. We also performed DFT simulation on the OER reaction pathways over Ir and Co sites of different facets parallelly on basis of the TEM results. The result reveals the synergy between Ir/Ru and Co resulting in the enhanced catalytic activities of both IrCoOx /RuCoOx and LaLi@Co3O4 toward OER.Acknowledgments:This work was supported by Overseas Outstanding Youth Fund project, shanghai Jiao Tong university, Shanghai, China; Shanghai Pujiang talent Plan, Shanghai, China; Argonne National Laboratory through Maria Goeppert Mayer Fellowship, US; State Key Laboratory of Metal Matrix Composites, shanghai Jiao Tong university, Shanghai, China. The works performed at Hydrogen research center, shanghai Jiao Tong university, and Argonne National Laboratory’s Center for Nanoscale Materials and Advanced Photo Source.Reference: K. Ayers et al., Annu. Rev. Chem. Biomol. Eng. 10, 219–239 (2019).M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy 38, 4901–4934 (2013).M. T. M. Koper, J. Electroanal. Chem. 660, 254–260 (2011).R. D. L. Smith et al., Science 340, 60–63 (2013).Chong et al., Science 380, 609–616 (2023).Chong et al., Adv. Energy Mater. 2023, 2302306.

Understanding the Role of Strain on Electrochemical Reaction Kinetics: Oxygen Evolution on Mechanically Strained Rutile TiO2 As a Model System

Electrocatalysis offers a green alternative (when coupled with renewably-sourced electrons) to conventional carbon-intensive chemical fuel and commodity production processes. Electrochemical device efficiency, however, is limited by the sluggish kinetics of multi-electron transfer reactions, such as the oxygen evolution reaction (OER). Theoretical adsorption free energy scaling relationships predict large oxygen evolution overpotentials (>370 mV) for metal oxides performing the adsorbate evolution mechanism, a series of four proton-concerted electron transfer steps.1 Identifying catalyst design strategies that overcome or “break” scaling relations (i.e. strain,2 high entropy alloys,3 non-concerted proton and electron transfer mechanisms4,5) would provide a means to lower kinetic potential energy penalties and enhance the efficiency and economic incentives for further development of renewably-driven electrochemical reactions.Here we investigate the role of mechanically induced strain on the OER activity of polycrystalline rutile TiO2 thin films, grown on the super elastic alloy nitinol (NiTi) and mechanically strained by tensile tester. Our work characterizes how strain manifests in these complex polycrystalline systems with complementary physical characterization techniques (e.g. X-ray diffraction and Raman spectroscopy) and relates strain to OER performance in alkaline electrolytes. We contextualize our results within the framework of conventional adsorption scaling relationships to hypothesize how tensile strain influences reaction intermediate adsorption affinities, inferring implications for the OER kinetics of benchmark IrO2 and RuO2 catalysts that share the same crystal structure as the rutile TiO2 considered here.(1) Jaramillo, T. F.; Nørskov, J. K.; Rossmeisl, J. Universality in Oxygen Evolution Electrocatalysis on Oxide Surfaces. ChemCatChem 2011, 3 (7), 1159–1165. https://doi.org/10.1002/cctc.201000397.(2) Khorshidi, A.; Violet, J.; Hashemi, J.; Peterson, A. A. How Strain Can Break the Scaling Relations of Catalysis. Nat Catal 2018, 1 (4), 263–268. https://doi.org/10.1038/s41929-018-0054-0.(3) Kante, M. V.; Weber, M. L.; Ni, S.; van den Bosch, I. C. G.; van der Minne, E.; Heymann, L.; Falling, L. J.; Gauquelin, N.; Tsvetanova, M.; Cunha, D. M.; Koster, G.; Gunkel, F.; Nemšák, S.; Hahn, H.; Velasco Estrada, L.; Baeumer, C. A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation. ACS Nano 2023, 17 (6), 5329–5339. https://doi.org/10.1021/acsnano.2c08096.(4) Grimaud, A.; Diaz-Morales, O.; Han, B.; Hong, W. T.; Lee, Y.-L.; Giordano, L.; Stoerzinger, K. A.; Koper, M. T. M.; Shao-Horn, Y. Activating Lattice Oxygen Redox Reactions in Metal Oxides to Catalyse Oxygen Evolution. Nature Chem 2017, 9 (5), 457–465. https://doi.org/10.1038/nchem.2695.(5) Yoo, J. S.; Rong, X.; Liu, Y.; Kolpak, A. M. Role of Lattice Oxygen Participation in Understanding Trends in the Oxygen Evolution Reaction on Perovskites. ACS Catal. 2018, 8 (5), 4628–4636. https://doi.org/10.1021/acscatal.8b00612.

Lanthanum Transition-Metal Sulfide Electrocatalysts for Overall Water Splitting

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.

Physically-Based Descriptors of the Nitrogen Reduction Reaction on Transition Metal Nitrides

Due to the high energy intensity and consequent carbon footprint of the Haber-Bosch process for ammonia production, researchers have been intensely studying the electrochemical nitrogen reduction reaction (NRR) as a means to directly produce ammonia using clean energy with lower emissions of carbon by-products. One exciting class of materials for NRR catalysis are transition metal nitrides (TMNs), as they have been shown to have good stability, flexible electronic structures, and decent electrochemical activity [1]. Previous studies using density functional theory (DFT) have explored the energetics of known NRR pathways (associative, dissociative, and Mars-van Krevelen) on the mononitrides of all naturally occurring d-block metals in rock salt and zincblende structures [2]. The most favorable NRR mechanism (determined to be the pathway that contains the smallest maximum potential change across all steps of the reaction) on these materials was shown to be the Mars-van Krevelen mechanism. Uncovering electronic, structural, and dynamic descriptors that correlate well with the energetics of this favorable NRR mechanism on TMNs will be useful in mitigating the need to run full DFT calculations when expanding the search space of potential catalyst candidates, such as ternary transition metal nitrides (TTMNs) and perovskite transition metal oxynitrides (TMONs). Previous literature has shown that the proton adsorption energy is a good descriptor for catalytic NRR activity on TMNs [3], oxygen vacancy content [4] and the oxygen p-band center of bulk perovskites [5] are good descriptors for catalytic oxygen evolution reaction performance, and the metal d-band center of pure transition metal catalysts is a good descriptor for reactivity and adsorption energies [6]. Inspired by these results, this work uses DFT on a set of TMNs to calculate a variety of potential physics-based descriptors, including: metal d and nitrogen p-band centers, hybridization between nitrogen p and metal d orbitals, nitrogen vacancy content, surface Bader charges, and phonon band centers. Since the energetics of the NRR can be modulated by the properties of either the atoms in the bulk or in the top surface layers, we calculate all of our descriptors from atoms in the TMN bulk form as well as from surface and subsurface atoms in the TMN slab form.Our results reveal several correlations between the descriptors and material attributes (such as adsorption energies and vacancy formation energies), which in turn govern the energetics of the NRR on the TMNs. We find that the N2 adsorption energy is negatively correlated with the metal d-band center, the N adsorption energy is positively correlated with the nitrogen p-band center, and both the proton adsorption energy and nitrogen vacancy formation energy are negatively correlated with nitrogen p and metal d orbital hybridization. Interestingly, we also find that for some attributes, the subsurface layer atoms dictate the attribute values and not the surface layer atoms. This suggests that heterogeneous catalysis reactivity may be modulated by atomic properties not purely from the bulk or purely from the surface, but rather from multiple subsurface layers as well.Overall, the insights gained from our descriptor analysis can be used to constrain the search and design space of future potential NRR catalysts, such as TTMNs and TMONs. In doing so, the descriptors can be used in future works in either a high-throughput screening or machine learning framework to allow for the inverse material design of optimal NRR catalysts. These optimal catalysts can in turn lead to the emergence of electrochemical ammonia synthesis in industrial production.References Qiao Z, Johnson D and Djire A. Cell Rep Phys Sci 2021; 2.Abghoui Y and Skúlason E. Catal Today 2017; 286: 69-77.Abghoui Y, Garden AL, Hlynsson VF, Björgvinsdóttir S, Ólafsdóttir H and Skúlason E. Physical Chemistry Chemical Physics 2015; 17: 4909-4918.Marelli E, Gazquez J, Poghosyan E, Müller E, Gawryluk DJ, Pomjakushina E, Sheptyakov D, Piamonteze C, Aegerter D, Schmidt TJ, Medarde M and Fabbri E. Angewandte Chemie - International Edition 2021; 60: 14609-14619.Jacobs R, Hwang J, Shao-Horn Y and Morgan D. Chemistry of Materials 2019; 31: 785-797.Nørskov JK, Abild-Pedersen F, Studt F and Bligaard T. Proc Natl Acad Sci U S A 2011; 108: 937-943.

Harvesting high-performance electro-water oxidation and selective MB degradation through dual functional Gd2O3–La2O3 photo-electrocatalysts

Interestingly, catalytic oxygen evolution reaction (OER) in an alkaline medium with minimizing the overpotential is the most trustworthy electrocatalyst for the output of hydrogen energy from copious water electrochemical activity. Currently, amalgamated trivalent cations metal oxides have gained desirability as a low-cost anode electrocatalyst to replace noble metal-supported electrocatalysts for water oxidation and are also used for photo-degradation applications. In the present work, we have successfully synthesized Gd2O3 supported La2O3 composites via hydrothermal pathways for efficient OER and selective methylene blue (MB) degradation applications. XRD, UV–Vis DRS, FT-IR, XPS, SEM-EDX, HR-TEM, DLS, and BET analyzers confirmed the successful synthesis of photo-electrocatalysts. Gd2O3–La2O3 composites achieved 5.66 and 3.37-fold larger surface areas than La2O3 and Gd2O3, respectively. The results of the Gd2O3 supported La2O3 composite electrode demonstrated better OER performance under 1 M KOH, and it exhibited a lower Tafel slope and overpotential of 72 mV dec−1 and 310 mV at 10 mA cm−2. A chronoamperometry examination confirms that the fabricated Gd2O3–La2O3 electrode has good stability at a fixed potential of 1.540 V vs. RHE for water oxidation. Although the, Gd+3 inspired La2O3 electrode actively takes part in OER activity owing to its high Cdl value of 40.222 μF cm−2. The selective degradation of MB dye using the Gd2O3–La2O3 composite achieved an acceptable degradation efficiency of 84.80 % compared to other pollutants under UV-light irradiation for 120 min, and the specified pH condition is 9 for the degradation of MB dye, and it follows the first-order kinetics model. Notably, post-OER and photocatalytic results exhibited good stability and reusability characteristics. Therefore, the Gd2O3–La2O3 catalyst can be used for real-time water oxidation and MB dye removal from polluted water.

Step-by-step enhancing oxygen evolution ability of CoFe2O4 by hybrid structure engineering and fluorine doping

CoFe2O4 is a very promising platform to catalyze oxygen evolution reaction (OER). Herein, the largely enhanced intrinsic performance of CoFe2O4 derived from the ZIF-67 for OER was demonstrated by step-by-step hybrid structure engineering and fluorine doping (F-Co/CoFe2O4@NC). This electrode showed high surface area, rapid charge transfer ability, and catalytic kinetics compared to the CoFe2O4@NC and Co/CoFe2O4@NC catalysts. Specifically, an overpotential of 280 mV was required to drive a kinetic current density of 10 mA cm−2 (loading on glassy carbon electrode, no iR-correction), with a Tafel slope of 49.7 mV dec-1 and remarkable catalytic stability throughout a 50-hour test. Theoretical analysis revealed a charge redistribution among Co, and Fe atoms was triggered by fluorine doping, and a more rapid active phase of CoOOH was generated on the surface during catalysis as confirmed by in-situ Raman spectroscopy and the post-surface chemical state analysis. The stable F atoms were more likely to be doped into CoFe2O4, and the active layer of CoOOH formed over the F-CoFe2O4 surface was more active than other states. Moreover, the electronic interaction induced by F-doping is more conducive to improving the adsorption energy of *OOH species, thereby improving the reaction kinetics and catalytic activity of OER. The current work showed an effective step-by-step approach to boosting the intrinsic activity of traditional catalysts for energy-relevant catalysis reactions.

Competitive Valerate Binding Enables RuO2-Mediated Butene Electrosynthesis in Water.

The (non)-Kolbe oxidation of valeric acid, sourced from a hydrolysis product of cellulose, provides a sustainable synthetic route to access value-added products, such as butene. An essential mechanistic step preceding product formation involves the oxidative and decarboxylative cleavage of a C-C bond. Yet, the role of the electrode surface in mediating this oxidative step remains an open question: the electron transfer can occur either via an inner-sphere or outer-sphere mechanism. Here, we report the electrochemical, in situ spectroscopic, computational, and reactivity studies of RuO2-mediated oxidative decarboxylation of valeric acid to butene in aqueous electrolytes. We find that carboxylates bind to RuO2 anode surfaces at potential values where decarboxylation products are observed. Our results are consistent with a reaction scheme where the competitive and catalytic oxygen evolution reaction (OER) is impeded by these bound carboxylate species while these species are inert toward butene formation. Our results implicate an outer-sphere electron transfer mechanism for decarboxylation where the surface chemistry of the RuO2 electrode serves to enable higher non-Kolbe reaction selectivity by suppressing the parasitic OER. Our findings delineate interfacial design principles for selective electrochemical systems that utilize water as the ultimate oxidant for sustainable decarboxylation.

Recycled Cathodes in Rechargeable Aqueous Batteries as Ready-Made Electrodes for Oxygen Evolution Catalysis.

The development of a low-cost and efficient oxygen evolution reaction (OER) electrode is of critical importance for water electrolysis technologies. The general approach to achieving a high-efficiency OER electrode is to regulate catalytic material structures by synthetic control. Here we reported an orthogonal approach to obtaining the OER electrode without intentional design and synthesis, namely, recycling MnO2 cathodes from failed rechargeable aqueous batteries and investigating them as ready-made catalytic electrodes. The recycled MnO2 cathode showed very little Zn2+ storage capacity but surprisingly high OER activity with a low overpotential of 307 mV at 10 mA cm-2 and a small Tafel slope of 77.9 mV dec-1, comparable to the state-of-the-art RuO2 catalyst (310 mV, 86.9 mV dec-1). In situ electrochemical and theoretical studies jointly revealed that the accelerated OER kinetics of the recycled MnO2 electrode was attributed to the enlarged active surface area of MnO2 and optimized electronic structure of Mn sites. This work suggests failed battery cathodes as successful catalysis electrodes for sustainable energy development.

Rational design of RuO2 composites from hydrogen-bonded organic frameworks for alkaline oxygen evolution reaction

In the past few decades, the task of creating electrocatalysts with consistent costs for facilitating oxygen evolution reactions with minimal overpotential remains a formidable challenge in the realm of chemical energy conversion technologies. In this report, we present a straightforward approach for synthesizing the melamine trithiocynauric acid (MTC) and ruthenium dioxide (RuO2) based, MTC/RuO2 composite, which demonstrates high efficiency in catalyzing oxygen evolution reaction. The physical characterizations for the prepared material are x-ray diffraction (XRD)， scanning electron microscopy (SEM), and x-ray photoelectron spectrometer (XPS) all approve the presence of RuO2 in the MTC composite structure. For oxygen evolution reaction the composite (MTC/RuO2-0.2) exhibited an exceptionally low overpotential of 190 mV for the current density of 10 mA cm−2 and also demonstrated a Tafel slope of 52 mV dec−1. Significant improvement in electrocatalytic activity is observed in alkaline electrolyte (1 M KOH). The outstanding behavior of the catalyst is due to the structural synergistic effect between MTC and RuO2. So far there is no report on RuO2-based hydrogen bonded organic frameworks for oxygen evolution reaction. The catalyst also shows high stability for almost 24 h. Hence, the MTC/RuO2-0.2 composite is highly unique and efficient.