Electrocatalysts For Oxygen Evolution Reaction Research Articles

Cation-induced interface electric field redistribution and molecular orbital coupling in Co-FeS/MoS2 for boosting electrocatalytic overall water splitting

A green hydrogen economy requires efficient bifunctional electrocatalysts for simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this study, a mild sulfuration strategy was used to create a Co-FeS/MoS2 catalyst from metal-organic frameworks (MOFs) on foam nickel. This catalyst exhibits exceptional activity in 1 M KOH, only requiring ultralow overpotentials of 63 mV and 230 mV to achieve current densities of 10 mA cm−2 and 100 mA cm−2 for the HER and OER processes. Additionally, it achieves a low cell voltage of 1.45 V at 10 mA cm−2, surpassing reported catalysts. DFT calculations and XPS tests show that Co introduction induces high-valence Fe active sites and facilitates interface electric field redistribution. Crystal orbital Hamilton population (COHP) calculations reveal d-p orbital hybridization, enhancing conductivity and charge transfer kinetics. This research sheds light on the catalytic impacts of metal cations on transition metal sulfides to design high efficient electrocatalysts.

Halloysite-derived hierarchical cobalt silicate hydroxide hollow nanorods assembled by nanosheets for highly efficient electrocatalytic oxygen evolution reaction

The oxygen evolution reaction (OER) is regarded as the bottleneck of electrolytic water splitting. Thus, developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is an ongoing scientific challenge. Herein, hierarchical hollow nanorods assembled with ultrathin mesoporous cobalt silicate hydroxide nanosheets (denoted as CoSi) were successfully fabricated, using the silica nanotube derived from halloysite as a sacrificial template, via a simple hydrothermal method. The resulting cobalt silicate hydroxide nanosheets stack with thicknesses ∼10 nm, as confirmed by transmission electron microscopy. The elaborated nanoarchitecture possesses a high specific surface area (SSA) allowing good exposure to the cobalt active centers exhibiting superior catalytic activity vs analogs synthesized using sodium silicate. Among all as-prepared CoSi samples, those synthesized at 150 °C (CoSi-150) exhibited the minimum overpotential of ∼347 mV at a current density of 10 mA cm–2. In addition, CoSi-150 also exhibited superior performance against typical cobalt-based catalysts, and its surface hydroxyl groups were beneficial for the enhancement of OER performance. Furthermore, the CoSi-150 showed excellent durability and stability after the 105 s chronopotentiometry test in 1 M KOH. This design concept provides a new strategy for the low-cost preparation of high-quality cobalt water splitting electrocatalysts.

Coupling Ir single atom with NiFe LDH/NiMo heterointerface toward efficient and durable water splitting at large current density

Developing efficient and robust bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at large current density is important to facilitate the industrial water splitting. Herein, a promising strategy is presented to couple Ir single atom with NiFe LDH/NiMo heterointerface. IrSA-NiFe LDH/NiMo requires ultralow overpotentials of 139/236 mV and 350/450 mV to deliver large current densities of 500 and 1000 mA cm−2 for HER/OER in 1 M KOH. Moreover, the electrode shows remarkable durability of 10000 cycles and long-term durability at 500 mA cm−2 over 500 h for both HER and OER. The water electrolyzer exhibits a low cell voltage of 1.84 V to attain 500 mA cm−2. The theoretical calculations decipher that the Ir single atom modulates the electronic property of catalyst, which tunes the adsorption strength of the key reaction intermediates and boosts the overall water splitting.

In-situ synthesis to promote surface reconstruction of metal–organic frameworks for high-performance water/seawater oxidation

Metal-organic frameworks (MOFs) have gained tremendous notice for the application in alkaline water/seawater oxidation due to their tunable structures and abundant accessible metal sites. However, exploring cost-effective oxygen evolution reaction (OER) electrocatalysts with high catalytic activity and excellent stability remains a great challenge. In this work, a promising strategy is proposed to regulate the crystalline structures and electronic properties of NiFe-metal-organic frameworks (NiFe-MOFs) by altering the organic ligands. As a representative sample, NiFe-BDC (BDC: C8H6O4) synthesized on nickel foam (NF) shows extraordinary OER activity in alkaline condition, delivering ultralow overpotentials of 204, 234 and 273 mV at 10, 100, and 300 mA cm−2, respectively, with a small Tafel slope of 21.6 mV dec−1. Only a slight decrease is observed when operating in alkaline seawater. The potential attenuation is barely identified at 200 mA cm−2 over 200 h continuous test, indicating the remarkable stability and corrosion resistance. In-situ measurements indicate that initial Ni2+/Fe2+ goes through oxidation process into Ni3+/Fe3+ during OER, and eventually presents in the form of NiFeOOH/NiFe-BDC heterojunction. The unique self-reconstructed surface is responsible for the low reaction barrier and fast reaction kinetics. This work provides an effective strategy to develop efficient MOF-based electrocatalysts and an insightful view on the dynamic structural evolution during OER.

Key Strategies for Continuous Seawater Splitting for Hydrogen Production: From Principles and Catalyst Materials to Electrolyzer Engineering

AbstractDue to the high cost of ultra‐pure water supply and the mismatch between water sources and renewable energy distribution, the large‐scale production of green hydrogen through seawater electrolysis has generated significant interest. This presents an attractive potential technology within the framework of carbon‐neutral energy production. However, owing to the complex composition of seawater, particularly the competitive oxidation reactions and corrosion issues involving Cl−, seawater electrolysis has suffered from low selectivity and poor stability in oxygen evolution reaction (OER), which severely impact the efficiency of hydrogen production and hinder the practical applications. To further promote in‐depth research and practical applications of seawater electrolysis, this review introduces the principles, key advantages, and challenges of seawater electrolysis. Specifically, the design strategies are categorized for highly active OER electrocatalysts for seawater electrolysis, including catalyst design, design of chemical reaction systems, and other special process design. To ensure long‐term operational stability of seawater electrolysis, various strategies such as employing self‐supporting materials, surface protection strategies, and electrolyzer design, are discussed. Finally, current challenges and future prospects for the industrialization of seawater electrolysis are proposed and discussed. It is expected that this review provides new insights for large‐scale seawater‐based hydrogen production in the future.

Fabrication of novel FeSe–GO composite: a highly efficient electro-catalyst for oxygen evolution reaction

Fabrication of novel FeSe–GO composite: a highly efficient electro-catalyst for oxygen evolution reaction

Key role of nonprecious oxygen-evolving active site in NiOOH electrocatalysts for oxygen evolution reaction

Nickel-based materials are the most promising electrocatalysts to date for the alkaline oxygen evolution reaction (OER). Identifying the phase transformation in the catalytic process and comparing the theoretical catalytic activity of different crystal facets are important for understanding OER mechanism and rational design. Herein, we calculate the theoretical catalytic activity of the basal plane and edge sites, respectively-two representative configurations in the OER-activate γ-phase NiOOH. DFT theoretical results suggest that the d-band center of Ni site in the basal plane configuration is −2.37 eV, which is closer to Fermi level than that of the edge configuration (−3.02 eV). The above results lead to the stronger adsorption capacity between the metal active sites and the oxygen intermediates. The consequence of Gibbs free energy indicates that the Ni site in the basal plane configuration (0.75 V) has slightly higher theoretical catalytic activity than the edge configuration (0.81 V). The charge density difference and Bader charge analysis results reveal that the hybridization interactions in the basal plane configuration are stronger and have more electron transfer between the surface Ni sites and absorbed OER intermediates. This present study highlights that regulating the optimal electronic structure of metal active site is conductive to high catalytic activity.

Non-Noble-Metal-Based Electrocatalysts for Acidic Oxygen Evolution Reaction: Recent Progress, Challenges, and Perspectives.

The oxygen evolution reaction (OER) plays a pivotal role in diverse renewable energy storage and conversion technologies, including water electrolysis, electrochemical CO2 reduction, nitrogen fixation, and metal-air batteries. Among various water electrolysis techniques, proton exchange membrane (PEM)-based water electrolysis devices offer numerous advantages, including high current densities, exceptional chemical stability, excellent proton conductivity, and high-purity H2. Nevertheless, the prohibitive cost associated with Ir/Ru-based OER electrocatalysts poses a significant barrier to the broad-scale application of PEM-based water splitting. Consequently, it is crucial to advance the development of non-noble metal OER catalysis substance with high acid-activity and stability, thereby fostering their widespread integration into PEM water electrolyzers (PEMWEs). In this review, a comprehensive analysis of the acidic OER mechanism, encompassing the adsorbate evolution mechanism (AEM), lattice oxygen mechanism (LOM) and oxide path mechanism (OPM) is offered. Subsequently, a systematic summary of recently reported noble-metal-free catalysts including transition metal-based, carbon-based and other types of catalysts is provided. Additionally, a comprehensive compilation of in situ/operando characterization techniques is provided, serving as invaluable tools for furnishing experimental evidence to comprehend the catalytic mechanism. Finally, the present challenges and future research directions concerning precious-metal-free acidic OER are comprehensively summarized and discussed in this review.

Highly Efficient CoFeP Nanoparticle Catalysts for Superior Oxygen Evolution Reaction Performance.

Developing effective and long-lasting electrocatalysts for oxygen evolution reaction (OER) is critical for increasing sustainable hydrogen production. This paper describes the production and characterization of CoFeP nanoparticles (CFP NPs) as high-performance electrocatalysts for OER. The CFP NPs were produced using a simple hydrothermal technique followed by phosphorization, yielding an amorphous/crystalline composite structure with improved electrochemical characteristics. Our results reveal that CFP NPs have a surprisingly low overpotential of 284 mV at a current density of 100 mA cm-2, greatly exceeding the precursor CoFe oxide/hydroxide (CFO NPs) and the commercial RuO2 catalyst. Furthermore, CFP NPs demonstrate exceptional stability, retaining a constant performance after 70 h of continuous operation. Post-OER characterization analysis revealed transformations in the catalyst, including the formation of cobalt-iron oxides/oxyhydroxides. Despite these changes, CFP NPs showed superior long-term stability compared to native metal oxides/oxyhydroxides, likely due to enhanced surface roughness and increased active sites. This study proposes a viable strategy for designing low-cost, non-precious metal-based OER catalysts, which will help advance sustainable energy technology.

Metallated graphynes as a bifunctional electrocatalyst for oxygen reduction and oxygen evolution reactions: A DFT study

Metallated graphynes as a bifunctional electrocatalyst for oxygen reduction and oxygen evolution reactions: A DFT study

Controlled synthesis of Sn doped Cu–Ni3S2 on Ni foam as efficient electrocatalyst for urea oxidation reaction and oxygen evolution reaction

Hydrogen production technology by urea-assisted electrocatalytic water decomposition has become one of the important means to alleviate carbon emissions and water pollution. In this paper, we first doped Sn and Cu element into the Ni3S2 material by hydrothermal method on the Ni foam support. This Cu–Sn–Ni3S2 material exhibits superior urea (potential of 1.42 V at 100 mA cm−2) and water oxidation (potential of 1.63 V at 100 mA cm−2) properties, which is one of the best electrochemical performance reported up to now. Analysis of experiment demonstrate that the increase in catalytic performance is assigned to faster charge transfer, more exposure of reaction centres and smaller resistance owing to doping of Sn and Cu. Density functional theory (DFT) analysis demonstrates that introduction of Sn and Cu increases the adsorption energy of urea and improves the conductivity of the Cu–Sn–Ni3S2 material, and the co-doping of the two changes the electron state density of the active site, thereby promoting the catalytic performance. This work provides insights into the development of efficient bifunctional electrodes for urea oxidation and oxygen evolution reaction through doping strategies.

Constructing Dual-Phase Co9S8-CoMo2S4 Heterostructure as an Efficient Trifunctional Electrocatalyst for Oxygen Reduction, Oxygen Evolution and Hydrogen Evolution Reactions.

Designing robust, efficient and inexpensive trifunctional electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is significant for rechargeable zinc-air batteries and water-splitting devices. To this end, constructing heterogenous structures based on transition metals stands out as an effective strategy. Herein, a dual-phase Co9S8-CoMo2S4 heterostructure grown on porous N, S-codoped carbon substrate (Co9S8-CoMo2S4/NSC) via a one-pot synthesis is investigated as the trifunctional ORR/OER/HER electrocatalyst. The optimized Co9S8-CoMo2S4/NSC2 exhibits that ORR has a half-wave potential of 0.86 V (vs. RHE) and the overpotentials at 10 mA cm-2 for OER and HER are 280 and 89 mV, respectively, superior to most transition-metal based trifunctional electrocatalysts reported to date. The Co9S8-CoMo2S4/NSC2-based zinc-air battery (ZAB) has a high open-circuit voltage (1.41 V), large capacity (804 mA h g-1) and highly stable cyclability (97 h at 10 mA cm-2). In addition, the prepared Co9S8-CoMo2S4/NSC2-based ZAB in series can self-drive the corresponding water electrolyzer. The dual-phase Co9S8-CoMo2S4 heterostructure provides not only multi-type active sites to drive the ORR, OER and HER, but also high-speed charge transfer channels between two phases to improve the synergistic effect and reaction kinetics.

Electrosynthesis of Transition Metal Coordinated Polymers for Active and Stable Oxygen Evolution

AbstractTransition metal coordination polymers (TM‐CP) are promising inexpensive and flexible electrocatalysts for oxygen evolution reaction in water electrolysis, while their facile synthesis and controllable regulation remain challenging. Here we report an anodic oxidation‐electrodeposition strategy for the growth of TM‐CP (TM=Fe, Co, Ni, Cr, Mn; CP=polyaniline, polypyrrole) films on a variety of metal substrates that act as both catalyst supports and metal ion sources. An exemplified bimetallic NiFe‐polypyrrole (NiFe‐PPy) features superior mechanical stability in friction and exhibits high activity with long‐term durability in alkaline seawater (over 2000 h) and anion exchange membrane electrolyzer devices at current density of 500 mA cm−2. Spectroscopic and microscopic analysis unravels the configurations with atomically distributed metal sites induced by d‐π conjugation, which transforms into a mosaic structure with NiFe (oxy)hydroxides embedded in PPy matrix during oxygen evolution. The superior catalytic performance is ascribed to the anchoring effect of PPy that inhibits metal dissolution, the strong substrate‐to‐catalyst interaction that ensures good adhesion, and the Fe/Ni−N coordination that modulates the electronic structures to facilitate the deprotonation of *OOH intermediate. This work provides a general strategy and mechanistic insight into building robust inorganic/polymer composite electrodes for oxygen electrocatalysis.

Electrosynthesis of Transition Metal Coordinated Polymers for Active and Stable Oxygen Evolution.

Transition metal coordination polymers (TM-CP) are promising inexpensive and flexible electrocatalysts for oxygen evolution reaction in water electrolysis, while their facile synthesis and controllable regulation remain challenging. Here we report an anodic oxidation-electrodeposition strategy for the growth of TM-CP (TM=Fe, Co, Ni, Cr, Mn; CP=polyaniline, polypyrrole) films on a variety of metal substrates that act as both catalyst supports and metal ion sources. An exemplified bimetallic NiFe-polypyrrole (NiFe-PPy) features superior mechanical stability in friction and exhibits high activity with long-term durability in alkaline seawater (over 2000 h) and anion exchange membrane electrolyzer devices at current density of 500 mA cm-2. Spectroscopic and microscopic analysis unravels the configurations with atomically distributed metal sites induced by d-π conjugation, which transforms into a mosaic structure with NiFe (oxy)hydroxides embedded in PPy matrix during oxygen evolution. The superior catalytic performance is ascribed to the anchoring effect of PPy that inhibits metal dissolution, the strong substrate-to-catalyst interaction that ensures good adhesion, and the Fe/Ni-N coordination that modulates the electronic structures to facilitate the deprotonation of *OOH intermediate. This work provides a general strategy and mechanistic insight into building robust inorganic/polymer composite electrodes for oxygen electrocatalysis.

Bimetallic Ni–Mn Electrocatalysts for Stable Oxygen Evolution Reaction in Simulated/Alkaline Seawater and Overall Performance in the Splitting of Alkaline Seawater

Bimetallic Ni–Mn Electrocatalysts for Stable Oxygen Evolution Reaction in Simulated/Alkaline Seawater and Overall Performance in the Splitting of Alkaline Seawater

Boosting the lattice oxygen reactivity of perovskite electrocatalyst via less Ru substitution

The successful deployment of efficient oxygen evolution reaction (OER) electrocatalysts is highly essential for multiple clean-energy-related conversion technologies. Perovskite oxides, with compositional diversity and elemental complexity, are a classic kind of OER electrocatalysts, whereas their activity remains insufficient under the traditional adsorbate evolution mechanism (AEM) due to limited scaling relations. Herein, taking the Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite as a model system, we find a less Ru substitution strategy to boost the lattice oxygen reactivity for improved OER. The OER behavior of BSCF is greatly ameliorated as Ru doping reaches an optimal level (BSCFR0.1), delivering a lowered overpotential by 45 mV at 10 mA cm−2. Notably, such doping remarkably triggers the generation of more surface oxygen vacancies, promotes internal charge transfer, and enlarges the surface hydrophilicity, hence facilitating more lattice oxygen to participate in the surface reaction. These results demonstrate the feasibility of Ru incorporation for ameliorating the OER behavior of perovskites, and such strategy can be further leveraged to design other remarkable perovskite-based OER catalytic materials.

A self‐powered system to electrochemically generate ammonia driven by palladium single atom electrocatalyst

AbstractThe utilization of single atoms (SAs) as trifunctional electrocatalyst for nitrogen reduction, oxygen reduction, and oxygen evolution reactions (NRR, ORR, and OER) is still a formidable challenge. Herein, we devise one‐pot synthesized palladium SAs stabilized on nitrogen‐doped carbon palladium SA electrocatalyst (Pd‐SA/NC) as efficient trifunctional electrocatalyst for NRR, ORR, and OER. Pd‐SA/NC performs a robust catalytic activity toward NRR with faradaic efficiency of 22.5% at −0.25 V versus reversible hydrogen electrode (RHE), and the relative Pd utilization efficiency is enhanced by 17‐fold than Pd‐NP/NC. In addition, the half‐wave potential reaches 0.876 V versus RHE, amounting to a 58‐time higher mass activity than commercial Pt/C. Moreover, the overpotential at 10 mA cm−2 is as low as 287 mV for Pd‐SA/NC, outperforming the commercial IrO2 by 360 times in turnover frequency at 1.6 V versus RHE. Accordingly, the assembled rechargeable zinc‐air battery (ZAB) achieves a maximum power density of 170 mW cm−2, boosted by 2.3 times than Pt/C–IrO2. Two constructed ZABs efficiently power the NRR‐OER system to electrochemically generate ammonia implying its superior trifunctionality.

Exploring the role of redox-active species on NiS-NiS2 incorporated sulfur-doped graphitic carbon nitride nanohybrid as a bifunctional electrocatalyst for overall water splitting

The advancement of effective and robust catalysts that can replace the precious-metal-based benchmarks for electrocatalytic overall water splitting is a highly fashionable approach to exploring sustainable energy utilization and addressing environmental issues. Herein, we demonstrate a facile single-step fabrication of NiS-NiS2 nanoparticles in situ grown on the layered porous sulfur-doped graphitic carbon nitride nanosheets (NiS-NiS2/SGCN) act as bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium.Further, an increasing the Ni precursor (fixed sulfur source) increases the formation of NiS-NiS2 on the surface of SGCN (labeled as NS-1.0, NS-2.0, and NS-3.0). Structural and morphological studies such as PXRD, XPS, FTIR, HR-TEM, etc., revealed a uniform distribution of NiS/NiS2 on the surface of S-g-C3N4 nanosheets. The OER and HER activity of NiS-NiS2/SGCN nanohybrid were significantly enhanced by increasing the affinity of accessible surface-active edge sites, interfacial contact allows effective modification of electronic structure, high structural porosity, redox-active centers of Ni2+/Ni3+, and rich in sulfur vacancy. In addition, the enhancement of the exposure of the edge sites is improved by their attachment to a sulfur-doped g-C3N4 framework. As a result, in the half-cell experiments, the NiS-NiS2/SGCN (NS-3.0) catalyst exhibited enhanced performance in both OER and HER, requiring an overpotential of 298 mV to reach 50 mA/cm2 for OER and −144 mV to reach 10 mA/cm2 for HER. Furthermore, the constructed electrolyzer using Ni-S 3.0 as the cathode and anode required a cell voltage of 1.66 V to yield 50 mA/cm2 in overall water splitting. This study may inspire the in-situ synthesis of different metal sulfides on SGCN to provide a unique interfacial approach for improving the performance of bifunctional non-precious electrocatalysts.

Ultrafine IrNi nanoparticles supported onto titanium nitride as low-iridium and highly active OER electrocatalysts for proton exchange membrane water electrolysis

The development of cost-effective and highly efficient iridium-based catalysts for the anode of proton exchange membrane water electrolyzers (PEMWEs) is urgently required. This study utilized a straightforward wet-chemical method to produce IrNi nanoparticles that were supported on titanium nitride (TiN), where the ultra-small particle size of 1.9 nm for IrNi nanoparticles and the structural support provided by TiN ensure the full exposure of catalytic sites. The electronic interaction between Ir-Ni and Ir-TiN enhances the intrinsic activity of the catalytic sites. The developed catalyst exhibits excellent oxygen evolution reaction (OER) performance, with an overpotential of just 267 mV at a current density of 10 mA cm−2, and a mass activity of 1.07 A mgIr−1 at 1.55 V versus reversible hydrogen electrode, which is more than 14 times that of commercial IrO2. Furthermore, its catalytic performance is validated in a PEMWE single cell, along with stable operation for 100 h. The proposed design of the supported iridium-based alloy catalysts in this study presents a novel and referential method for developing anode catalysts in PEMWEs.

2D NiFe2O4/Ni(OH)2 Heterostructure-Based Self-Supporting Electrode With Synergistic Surface/Interfacial Engineering for Efficient Water Electrooxidation.

To meet the industrial demand for overall water splitting, oxygen evolution reaction (OER) electrocatalysts with low-cost, highly effective, and durable properties are urgently required. Herein, a facile confined strategy is utilized to construct 2D NiFe2O4/Ni(OH)2 heterostructures-based self-supporting electrode with surface-interfacial coengineering, in which abundant and ultrastable interfaces are developed. Under the high molar ratio of Ni/Fe, both spinel oxide and hydroxides phases are formed simultaneously to obtain 2D NiFe2O4/Ni(OH)2 heterostructure. The in-depth analysis indicates that the NiFe2O4/Ni(OH)2 interface displays strong electronic interactions and triggers the formation of crystalline-amorphous coexisting catalytic active NiOOH. Meanwhile, the stable catalyst-collector interface favors the electron transfer and oxygen molecules transport. The resultant 2D NiFe2O4/Ni(OH)2@CP electrode exhibits superior OER performance, including a low overpotential of 389mV and a long operating time of 12h at 1Acm-2. This work paves a novel method for fabricating efficient and low-cost electrocatalysts for electrochemical conversation devices.