Oxygen Evolution Electrocatalysts Research Articles

Iron-Based Layered Perovskite Oxyfluoride Electrocatalyst for Oxygen Evolution: Insights from Crystal Facets with Heteroanionic Coordination.

Mixed-anion compounds have recently attracted attention as solid-state materials that exhibit properties unattainable with those of their single-anion counterparts. However, the use of mixed-anion compounds to control the morphology and engineer the crystal facets of electrocatalysts has been limited because their synthesis method is still immature. This study explored the electrocatalytic properties of a Pb-Fe oxyfluoride, Pb3Fe2O5F2, with a layered perovskite structure for oxygen evolution reaction (OER) and compared its properties in detail with those of a bulk-type cubic three-dimensional (3D) perovskite, PbFeO2F. A Pb3Fe2O5F2 electrode prepared with carbon nanotubes and a graphite sheet as a conductive support and a substrate, respectively, demonstrated better OER performance than a PbFeO2F electrode. The role of specific crystal facets of Pb3Fe2O5F2 in enhancing the OER activity was elucidated through electrochemical analysis. Density functional theory calculations indicated that the Pb3Fe2O5F2 (060) facet with Fe sites exhibited a lower theoretical overpotential for the OER, which was attributed to a moderately strong interaction between the active sites and the reaction intermediates; this interaction was reinforced by the strong electron-withdrawing behavior of fluoride ions. This finding offers new insights for developing efficient electrocatalysts based on oxyfluorides, leveraging the high electronegativity of fluorine to optimize the electronic states at active sites for the OER, without relying on precious metals.

Enabling High‐Rate and Long‐Cycling Zinc–Air Batteries with a ΔE = 0.56 V Bifunctional Oxygen Electrocatalyst

AbstractZn–air batteries (ZABs) are promising next‐generation energy storage devices due to their low cost, intrinsic safety, and environmental benignity. However, the sluggish kinetics of the cathodic reactions severely limits the ZAB performances in practical use, calling for high‐efficiency bifunctional oxygen reduction and evolution electrocatalysts. Herein, an ultrahigh‐active bifunctional electrocatalyst is developed with a record‐low ΔE of 0.56 V, significantly outperforming the noble‐metal‐based benchmark (Pt/C+Ir/C, ΔE = 0.77 V) and many other reported bifunctional electrocatalysts (mostly ΔE ≥ 0.60 V). The nanoscale composite of Fe‐based single‐atom sites and nanosized layered double hydroxides endows the bifunctional electrocatalyst with high conductivity and a large active surface that afford strengthened electron conduction and ion transport pathways. Furthermore, a remarkable improvement in stability is realized following the current division principle. ZABs with the bifunctional electrocatalyst deliver a high peak power density of 198 mW cm−2 and excellent cycling durability for over 6000 cycles. Moreover, ampere‐hour‐scale ZABs are constructed and cycled under 1.0 A and 1.0 Ah conditions. This work breaks the activity record for bifunctional oxygen electrocatalysis and expands the potential of ZABs for sustainable energy storage.

Reinforcement of electrocatalytic overall water splitting by constructing Mo-doped NiFe LDH/NiS heterostructure

Electrochemical water splitting is considered to be an environmentally friendly and efficient method of hydrogen production. NiFe LDH is a well-known electrocatalyst for oxygen evolution, yet its effectiveness in HER has been suboptimal. In this research, we created a Mo-NiFe LDH@NiS catalyst on carbon cloth via cation doping and heterointerface construction of NiFe LDH. The resulting Mo-NiFe LDH@NiS/CC showed remarkable HER activity. Furthermore, when used as a bifunctional electrode for overall water splitting, Mo-NiFe LDH@NiS/CC operated at a cell voltage of 1.58V at a current density of 10mA/cm² and exhibited outstanding durability. This study emphasizes the significant enhancement in HER and overall water-splitting efficiency of NiFe LDH achieved through Mo doping and heterostructure engineering, advancing its potential for effective water splitting applications.

Electrocatalytic activities of iron-supported N-doped porous carbon towards the oxygen/hydrogen evolution reaction

Red mud (RM) disposal has been highly apprehensive due to its environmental impact. The aluminum industry produces large amounts of red mud waste annually, and turning it into a value-added product is a key component of sustainable development. This study combines RM with an N-doped porous carbon (biomass precursor) as an effective electrocatalyst for oxygen evolution and hydrogen evolution reactions (OER and HER). One significant obstacle to anion-exchange membrane (AEM) electrolyzer applications is the development of electrocatalysts that do not require noble metals and are both efficient and effective at HER and OER. The synthesized iron-supported (RM-derived) N-doped porous carbon (RMNPC) exhibits excellent catalytic activities with 276 and 191 mV overpotentials at 10 mA cm−2 for OER and HER, respectively. A two-electrode cell system is designed with an RMNPC/NF electrode as anode and cathode, and it necessitates just 1.82 V to realize 10 mA cm−2 and shows outstanding durability. This study presents a low-cost but effective electrocatalyst for water splitting for renewable hydrogen production, achieving the goal of RM recycling and highlighting the potential of porous carbon electrocatalysts.

Chemical Bath Deposition of NiFe Alloy Anode for Efficient Alkaline Water Electrolyzer Integration.

Green hydrogen production from water splitting is a feasible way for intermittent renewable energy storage and utilization, where the exploration and scale-up preparation of high-performance anodic oxygen evolution electrocatalysts are critical prerequisites for its industrial-level applications. Herein, a chemical bath deposition of FeNi3 intermetallic alloys onto Ni mesh support is performed, which delivers a current density of 0.62 Acm-2 at 1.72 V versus reversible hydrogen electrode for alkaline water oxidation in 1 m KOH and an excellent electrolysis stability at 0.2 A cm-2 for over 300 h. Moreover, via 3D computational fluid dynamics simulation and flow field optimization, a homogeneous deposition of ≈5400 cm2 NiFe anode is demonstrated within 4 min using the developed flow bath reactor. Once integrating the as-prepared NiFe anodes into alkaline electrolyzer stack, the voltage variation between each unit cell is below 40 mV at a total operation current of 71 A, or ca. current density of 0.2 A cm-2, confirming the uniformity of this batch synthesis protocol and its great potential for industrial alkaline water electrolysis.

Fluorine-doped carbon dots decorated on iron-cobalt selenide nanosheets as superior electrocatalysts for oxygen evolution in seawater

Developing oxygen evolution reaction (OER) catalysts that can efficiently and stably operate at high current densities in seawater electrolysis is urgently demanded but challenging. In this study, selenium-vacancies-rich iron-cobalt selenide nanosheets (FeCoSe-VSe) decorated with fluorine-doped carbon dots (FCDs) are rationally designed and prepared on nickel foams (NF) through the successive processes of hydrothermal treatment and selenization. Benefiting from the large accessible surface area and abundant active sites provided by FCDs and selenium vacancy defects, as well as the coupled interface between FCDs and FeCoSe-VSe that optimizes the oxygen adsorption energy and accelerates the kinetic process, the FCDs/FeCoSe-VSe/NF composite exhibits excellent OER catalytic activities with a low overpotential of 258 mV at a current density of 200 mA cm−2 in 1 M KOH and a small Tafel slope of 34.7 mV dec–1. In the electrolytes of simulated and natural seawater, the overpotentials of the FCDs/FeCoSe-VSe/NF electrode are slightly higher, measured to be 264 and 297 mV, respectively. More profoundly, the introduction of FCDs enhances the corrosion resistance of the catalyst in alkaline electrolytes, ensuring the long-term stability. This work offers a guidance to improve the electrochemical performances of catalysts for high-efficiency seawater oxidation.

NiFe‐Based Electrocatalysts for Alkaline Oxygen Evolution: Challenges, Strategies, and Advances Toward Industrial‐Scale Deployment

NiFe‐Based Electrocatalysts for Alkaline Oxygen Evolution: Challenges, Strategies, and Advances Toward Industrial‐Scale Deployment

NiO/ATO as an efficient bifunctional electrocatalysts for oxygen evolution and urea oxidation reactions

In this study, Ni-MOF-derived NiO was mixed with various weights of commercial antimony-doped tin oxide (ATO) using a simple and efficient hydrothermal method to synthesize composites denoted as AN-1, AN-2, and AN-3, which were subsequently characterized using a variety of physicochemical methods. The as-prepared materials were used as bifunctional electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR). In the UOR, the AN-1 electrocatalyst exhibited excellent performance compared to the other electrocatalysts. In a 1.0 M KOH aqueous electrolyte, the OER onset potential was approximately 1.64 V, whereas, in the UOR, the overpotential was 1.38 V (vs RHE), which is lower than that of the OER. The AN-1 electrocatalyst showed lower Tafel slope values in both the OER and UOR studies: 173 mV dec−1 and 109mV dec−1, respectively.

FeNi nanoparticle-modified reduced graphene oxide as a durable electrocatalyst for oxygen evolution

Clean energy transition and decarbonization through hydrogen technology hold a crucial role in revitalizing a sustainable world. The development of catalysts free of precious elements to facilitate the water splitting process in an electrolyser represents a key sustainable goal to lower the production cost of green hydrogen fuel, therefore improving its accessibility and affordability. Here we report a hybrid electrocatalyst for oxygen evolution reaction (OER) in alkaline media with high stability and low overpotential, free of precious metals and rare elements. The hybrid catalyst is composed of laser-generated Fe50Ni50 nanoparticles (FeNi NPs) dispersed on reduced graphene oxide (rGO) and deposited on FeNi layered double hydroxide (FeNi LDH) grown on Ni foam substrate. The prepared FeNi-rGO/FeNi/Ni foam hybrid catalyst requires an overpotential of only 234 mV at a current density of 10 mA/cm2, which is 37 mV lower than the tested commercial RuO2 catalyst on Ni foam substrate. Besides, the hybrid catalyst is extremely robust; it stands 10,000 cycles of accelerated deterioration and runs for more than 1,300 h at a current density of 10 mA/cm2 without performance decay.

Integrating Multiple Strategies Using Biotechnology to Design High‐Performance Electrocatalysts for Hydrogen and Oxygen Evolution

AbstractCombining multiple design strategies often enhances catalyst performance but usually comes with high costs and low reproducibility. A technique that enhances catalyst performance in multiple strategies is urgently needed. Herein, a novel bioregulation technique is introduced, allowing simultaneous control over morphology, particle size, doping, interface engineering, and electronic properties. Bioregulation technique utilizes the soluble extracellular polymer from Aspergillus niger as a templating agent to construct high‐performance catalysts for hydrogen and oxygen evolution reaction (HER and OER). This technique controls catalyst morphology, introduces biological N and S doping, and regulates the electronic structure of the catalyst surface. Biomolecule modification enhances surface hydrophilicity, and the nanostructure increases surface roughness and gas‐release efficiency. Theoretical calculations show that the bioregulation technique shortens the d/p‐band center, optimizing reaction intermediate adsorption and desorption. The Bio‐Pt/Co3O4 catalyst with trace Pt on the surface, designed with these strategies, achieves HER (η10 of 42 mV), OER (η10 of 221 mV), and overall water‐splitting performance (1.51 V at 10 mA cm−2), maintaining stability for over 50 h, outperforming most Pt‐based catalysts. Notably, using spent lithium‐ion battery cathodes leachate, rich in Co2⁺, successfully replicates the experiment. This approach holds promise as a mainstream method for synthesizing high‐performance materials in the future.

Machine learning-assisted dual-atom sites design with interpretable descriptors unifying electrocatalytic reactions

Low-cost, efficient catalyst high-throughput screening is crucial for future renewable energy technology. Interpretable machine learning is a powerful method for accelerating catalyst design by extracting physical meaning but faces huge challenges. This paper describes an interpretable descriptor model to unify activity and selectivity prediction for multiple electrocatalytic reactions (i.e., O2/CO2/N2 reduction and O2 evolution reactions), utilizing only easily accessible intrinsic properties. This descriptor, named ARSC, successfully decouples the atomic property (A), reactant (R), synergistic (S), and coordination effects (C) on the d-band shape of dual-atom sites, which is built upon our developed physically meaningful feature engineering and feature selection/sparsification (PFESS) method. Driven by this descriptor, we can rapidly locate optimal catalysts for various products instead of over 50,000 density functional theory calculations. The model’s universality has been validated by abundant reported works and subsequent experiments, where Co-Co/Ir-Qv3 are identified as optimal bifunctional oxygen reduction and evolution electrocatalysts. This work opens the avenue for intelligent catalyst design in high-dimensional systems linked with physical insights.

CoFe-LDHs were grown on Co-layered hydroxides to achieve 3D-hierarchical flower like architecture for efficient oxygen evolution reaction

In this work, we have successfully synthesized an efficient and cost-effective electrocatalyst for alkaline oxygen evolution (OER) using a solvothermal method combined with an ion exchange strategy. Firstly, single Co-layer hydroxides (Co-LHs) were synthesized by a one-step solvothermal method. Subsequently, [Fe(C2O4)3]3- was introduced onto the Co-LHs surface to facilitate ion exchange, and a further CoFe-layered double hydroxides (CoFe-LDHs) layer was grown on the Co-LHs material surface to finally obtain the nanoflower-like Co-LHs@CoFe-LDHs composite. Related material characterization results showed that C2O42- was successfully inserted into the interlayer structure of the LDHs, resulting in an increase in interlayer spacing. In situ Raman spectroscopy revealed that the active site of the OER reaction in the Co-LHs@CoFe-LDHs material was CoOx. Thanks to the double structure of the LDHs improving charge transfer ability and the synergy between cobalt and iron species, Co-LHs@CoFe-LDHs showed significantly enhanced OER performance. This study provides new insights and methods for the development of novel LDHs structural electrocatalysts.

Breaking the Bottleneck of Activity and Stability of RuO2-Based Electrocatalysts for Acidic Oxygen Evolution.

Electrochemical acidic oxygen evolution reaction (OER) is an important part for water electrolysis utilizing a proton exchange membrane (PEM) apparatus for industrial H2 production. RuO2 has garnered considerable attention as a potential acidic OER electrocatalyst. However, the overoxidation of Ru active sites under high potential conditions is usually harmful for activity and stability, thereby posing a challenge for large-scale commercialization, which needs effective strategies to circumvent the leaching of Ru and further activate Ru sites. Herein, a Mini-Review is presented to summarize the recent developments regarding the activation and stabilization of the Ru active sites and lattice oxygen through the modulation of the d-band center, coordination environment, bridged heteroatoms, and vacancy engineering, as well as structural protection strategies and reaction pathway optimization to promote the acidic OER activity and stability of RuO2-based electrocatalysts. This Mini-Review offers a profound understanding of the design of RuO2-based electrocatalysts with greatly enhanced acidic OER performances.

Deciphering the work function induced local charge regulation towards activating an octamolybdate cluster-based solid for acidic water oxidation.

The advancement of highly robust and efficient electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions is imperative for the sustainable production of green hydrogen. In accomplishing sustainable and sturdy electrocatalysts for oxygen evolution at low pH, the challenge is tough for non-iridium/ruthenium-based electrocatalysts. This study elaborates on the intrinsic alterations in electronic arrangements and structural disorder upon the precise activation of an octamolybdate cluster-based solid [{Cu(pz)4}2Mo8O26]·2H2O through room temperature grinding with rGO (reduced graphene oxide), resulting in enhanced conductivity, stability, and activity of the electrocatalyst towards the acidic OER without employing any benchmark metal ion (Ru or Ir). Additionally, the work function of the composites was found to be low compared to that of pristine polyoxometalates (POMs), indicative of the improved conducive behavior, which is lacking in the POM structure. The catalyst displays a notably reduced overpotential of 185 mV to achieve a current density of 10 mA cm-2, coupled with significant stability lasting 24 hours at a higher current density of 100 mA cm-2. These findings propose the manipulation of crystalline POMs with highly conductive non-metallic elements to facilitate superior water oxidation at lower pH levels which can help in the production of green hydrogen.

Structural and Compositional Optimization of Fe-Co-Ni Ternary Amorphous Electrocatalysts for Efficient Oxygen Evolution in Anion Exchange Membrane Water Electrolysis.

Anion exchange membrane water electrolysis (AEMWE) offers a sustainable path for hydrogen production with advantages such as high current density, dynamic responsiveness, and low-cost electrocatalysts. However, the development of efficient and durable oxygen evolution reaction (OER) electrocatalysts under operating conditions is crucial for achieving the AEMWE. This study systematically investigated Fe-Co-Ni ternary amorphous electrocatalysts for the OER in AEMWE through a comprehensive material library system comprising 21 composition series. The study aims to explore the relationship between composition, degree of crystallinity, and electrocatalytic activity using ternary contours and binary plots to derive optimal catalysts. The findings reveal that higher Co and lower Fe contents lead to increased structural disorder within the Fe-Co-Ni system, whereas an appropriate amount of Fe addition is necessary for OER activity. It is concluded that the amorphous structure of Fe-Co3-Ni possesses an optimal ternary composition and degree of crystallinity to facilitate the OER. Post-OER analyses reveal that the optimized ternary amorphous structure induces structural reconstruction into an OER-favorable OOH-rich surface. The Fe-Co3-Ni electrocatalysts exhibit outstanding performances in both half-cells and single-cells, with an overpotential of 256mV at 10mAcm- 2 and a current density of 2.0 Acm- 2 at 1.89V, respectively.

Earth-Abundant Divalent Cation High-Entropy Spinel Ferrites as Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

Earth-Abundant Divalent Cation High-Entropy Spinel Ferrites as Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

Ce-doped cobalt-based hydroxide assisted with low-temperature molten salt for industrial oxygen evolution reaction

Developing low cost and high-performance oxygen evolution electrocatalysts is significant to improve the efficiency of water electrolysis for large-scale hydrogen production. Cobalt hydroxide is a promising electrocatalyst for oxygen evolution reaction (OER), but its poor conductivity and activity seriously restrict the practical application. A simple one-step low temperature molten salt method was applied to successfully synthesize the Ce-doped cobalt hydroxide nitrate (Ce-CoNH/CF), which exhibits outstanding OER performance with a low overpotential of 448 mV at the current density of 1000 mA/cm2 in 1 mol/L KOH. The remarkable performance of Ce-CoNH/CF electrode in OER may be the comprehensive result of fast reaction kinetics, large electrochemical active specific surface area (ECSA) and small charge transfer resistance (Rct) as revealed by the Tafel, cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) analysis. Under the simulated industrial test conditions (6 mol/L KOH, 70 °C), the Ce-CoNH/CF electrode still displays excellent OER performance.

Photo‐induced Intercalation of Cobalt(II) Tellurium Oxide as an Oxygen Evolution (Photo)electrocatalyst

Photo‐induced Intercalation of Cobalt(II) Tellurium Oxide as an Oxygen Evolution (Photo)electrocatalyst

Scaling Up Stability: Navigating from Lab Insights to Robust Oxygen Evolution Electrocatalysts for Industrial Water Electrolysis

AbstractIn the pursuit of sustainable hydrogen production via water electrolysis, paramount importance of electrocatalyst stability emerges as a defining factor for long‐term industrial viability. A thorough understanding and enhancement of stability not only ensure extended catalyst lifetimes but also pave the way for consistent and efficient hydrogen generation. This review focuses on the pivotal role of stability in determining the practical viability of oxygen evolution electrocatalysts (OECs) for large‐scale applications in water electrolysis for hydrogen production. The paper explores the pivotal role of stability over initial activity, citing examples and hypothetical scenarios. First, figures of merits for stability evaluation of the electrocatalyst are explained along with the available benchmarking protocols for stability evaluation. Further, the text delves into various strategies that can enhance the stability of the electrocatalyst which include self‐healing/regeneration pathway, oxygen evolution reaction (OER) mechanism optimization to achieve highly stable OER and stabilization of active metals atoms within the electrocatalyst to inhibit dissolution as a way forward for industrial application. The interplay of stability, activity, and cost is also explained to suit the industrial application of the electrocatalyst. Lastly, it outlines challenges, prospects, and future directions, presenting a guide for advancing OECs in the hydrogen generation landscape.

LaCo0.2Fe0.8O3 perovskites doped with natural Ca2+ as bifunctional electrocatalysts for oxygen evolution and reduction reactions.

Perovskite oxides are promising electrocatalysts for various energy applications due to their exceptional catalytic activity, flexible architecture, and low cost. In this study, LCFO was doped with different ratios of Ca2+ from eggshells, resulting in dual-purpose electrocatalysts for oxygen reduction and evolution processes. The nanoparticles were characterized using various techniques, including Brunauer-Emmett-Teller analysis and XRD. Results clarified the relative surface area and roughness, increasing with Ca2+ doping. LCFO also demonstrated highly magnetic properties, improved charge transfer, catalytic activity, and long-term durability. The results demonstrated the perovskite's cost-effectiveness as a bifunctional electrocatalyst, and the role of Ca2+ in enhancing its properties. La0.6Ca0.4Co0.2Fe0.8O3(LCCFO-0.4) showed higher magnetic properties (M s = 13.36 emu g-1 and M r = 2.54 emu g-1). The LCFO sample showed a current density of 5.13 mA cm-2 and 3 mA cm-2 for OER and ORR respectively, at E onset 1.7 V and 0.57 V (vs. RHE). The LCFO electrochemical active surface area is 0.033 cm2.