Oxygen Evolution Reaction Activity Research Articles

Dodecylamine‐Assisted Hydrothermal Synthesis of Carbon‐Supported Ultrafine IrRu Nanoparticles for Oxygen Evolution Electrocatalysis and Overall Water Splitting

AbstractRuthenium (Ru)‐ and iridium (Ir)‐based nanomaterials have always been regarded as efficient electrocatalysts for oxygen evolution reaction (OER) in acidic electrolytes. Herein, we develop a facile dodecylamine‐assisted hydrothermal synthesis for producing carbon‐supported IrRu alloy nanoparticles with controllable Ir/Ru ratios and ultrafine sizes towards high‐efficiency OER and overall water electrolysis. In this strategy, the dodecylamine that serves as a capping and reducing agent enables the final IrRu alloy nanoparticles to possess average sizes <3 nm and high degree of dispersion on carbon substrate. By combining high OER activity of Ru with high acidic robustness of Ir, the as‐prepared IrRu/C nanoparticles at a suitable Ir/Ru ratio of 1/3 show good activity and durability for the OER electrocatalysis and overall water splitting. In specific, the Ir1Ru3/C catalyst exhibits the lowest overpotential of 302 mV at the current density of 10 mA cm−2 and the highest mass activity of 120.5 mA mg−1 at 1.532 V for OER in 0.5 M H2SO4 electrolyte. In addition, a two‐electrode acidic electrolyzer assembled with Ir1Ru3/C at anode and commercial Pt/C at cathode (Pt/C|| Ir1Ru3/C) exhibits a low cell voltage of 1.44 V for achieving the current density of 10 mA cm−2, along with a satisfied 20h durability.

Modulating RuO2 Electrocatalysis via Introducing Lanthanides for Enhanced Acidic Oxygen Evolution

AbstractThe low activity of ruthenium dioxide (RuO2) and the rapid dissolution of the ruthenium (Ru) site during acid oxygen evolution reaction (OER) at high current density restricts its application in proton exchange membrane (PEM) electrolyzers. In this work, a series of rare‐earth (RE) elements doped RuO2 nanorods is developed as high‐performance OER electrocatalysts. X‐ray absorption spectroscopy suggests that RE doping regulates the local coordination environment around Ru sites, lowers the valance of Ru, and shortens the Ru─O─Ru(M) bond length, which enhances structural stability. Among the RE‐RuO2 samples, Sm‐RuO2 exhibits remarkable performance with a low overpotential of 283 mV to reach 100 mA cm−2 and maintained stability for over 140 h at 10 mA cm−2. Moreover, the PEM electrolyzer using Sm‐RuO2 as the anode can be stably operated at 500 mA cm−2 for 15 h. Electrochemical analysis, X‐ray photoelectron spectroscopy, and in situ Raman spectroscopy show that Sm doping lowers the d‐band center, reduces the adsorption energy of O intermediates to enhance the OER activity, and restrains excessive oxidation of Ru sites while stabilizing lattice oxygen during the OER process, thereby enhancing OER stability. This work offers valuable insights into improving the stability of metal oxide catalysts in acidic electrolytes.

On the Quest for Oxygen Evolution Reaction Catalysts Based on Layered Double Hydroxides: An Electrochemical and Chemometric Combined Approach

The oxygen evolution reaction (OER) is a crucial process in various energy conversion and storage technologies, such as water electrolysis. Developing efficient and cost‐effective electrocatalysts is essential to achieve the commercialization of devices for the transition toward sustainable energy solutions. Herein, ternary layer double hydroxides (LDHs) are synthesized and characterized as electrocatalysts for OER using a potentiodynamic electrochemical deposition method on Grafoil. A chemometric approach based on experimental design is employed to rationalize the effort in the investigation of the LDHs which are based on Ni, Co, and Fe. The deposited films are characterized using cyclic voltammetry and X‐ray diffraction to determine peak currents and potentials, and crystal size. Furthermore, the electrocatalyst performances are assessed by linear sweep voltammetry in 1M KOH from which the Tafel slope and onset potential are calculated. The obtained data are used to derive models describing the material properties and electrocatalyst performance as a function of the electrolyte composition used during the LDHs electrodeposition. This study provides valuable insights into the relationship between the electrocatalyst composition and its OER activity, enabling the design of more efficient and sustainable electrochemical systems for energy applications.

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.

Synergistic Interplay between Fe-based Perovskite Oxides and Co in Electrolyte for Efficient Oxygen Evolution Reaction.

Perovskite oxides have been extensively investigated as active electrocatalysts for the oxygen evolution reaction (OER) in alkaline solution. While the OER activity of some perovskite oxides is positively influenced by Fe ions in the electrolyte, the impact of other transition metal ions in the electrolyte remains unclear. In this study, we compared the influence of Co ions intentionally added to the electrolyte on the OER activities of two Fe-based perovskite oxides (Ba0.5Sr0.5FeO3-δ and LaFeO3). While the OER activity ofBa0.5Sr0.5FeO3-δis significantly enhanced by adding Co ions to the electrolyte, LaFeO3 showed little difference in the OER behavior between the Co-free and Co-containing electrolytes. In the case of Ba0.5Sr0.5FeO3-δ, an amorphous layer was formed, and the Co ions from the electrolyte were incorporated on the surface as a result of OER cycling. On the other hand, Co ions were also detected on the surface ofLaFeO3, but its crystalline structure remains unchanged during the OER. Our study suggests that synergistic interplay between the perovskite oxides undergoing a structural transformation at the surface and transition metal ions in the electrolyte can improve the OER activity.

Hydrothermal-Induced Cationic Vacancies in NiAl Hydroxide for Enhanced Oxygen Evolution Activities through Optimization of eg* Band Broadening.

Nickel-based hydroxides [Ni(OH)2] have attracted significant attention as effective oxygen evolution reaction (OER) catalysts. In recent years, defect engineering has been extensively utilized in Ni(OH)2 modification research. Numerous studies have confirmed that the generation of defects can expose more active sites and regulate electronic states, particularly through the introduction of Al cationic vacancies, which enhance conductivity and thereby improve the catalytic performance. The traditional method for producing cationic vacancies is electrochemical etching. However, this method generates a limited number of vacancies in the catalysts and has the complex etching process. Herein, we found that when NiAl layered double hydroxides were treated using a hydrothermal process at 100 °C in a KOH solution, more Al cationic vacancies were generated. Compared to the traditional method with an Al leaching efficiency of 24%, our proposed method achieved an Al leaching efficiency of 44%. Meanwhile, the electrochemical results showed that the overpotential was reduced by 110 mV at 10 A/g. Further experiments showed that the enhanced OER activities resulting from an increased number of cationic defects lead to structural distortions, which broaden the eg* band, significantly affecting the rate of electron transfer between the electrocatalyst and external circuitry, thereby enhancing the OER activity. This work presents a promising approach to creating cationic defects in Ni(OH)2 for high-performance electrocatalysts.

Reactivity and Stability of Reduced Ir-Weight TiO2-Supported Oxygen Evolution Catalysts for Proton Exchange Membrane (PEM) Water Electrolyzer Anodes.

Reducing the iridium demand in Proton Exchange Membrane Water Electrolyzers (PEM WE) is a critical priority for the green hydrogen industry. This study reports the discovery of a TiO2-supported Ir@IrO(OH)x core-shell nanoparticle catalyst with reduced Ir content, which exhibits superior catalytic performance for the electrochemical oxygen evolution reaction (OER) compared to a commercial reference. The TiO2-supported Ir@IrO(OH)x core-shell nanoparticle configuration significantly enhances the OER Ir mass activity from 8 to approximately 150 A gIr-1 at 1.53 VRHE while reducing the iridium packing density from 1.6 to below 0.77 gIr cm-3. These advancements allow for viable anode layer thicknesses with lower Ir loading, reducing iridium utilization at 70% LHV from 0.42 to 0.075 gIr kW-1 compared to commercial IrO2/TiO2. The identification of the Ir@IrO(OH)x/TiO2 OER catalyst resulted from extensive HAADF-EDX microscopic analysis, operando XAS, and online ICP-MS analysis of 30-80 wt % Ir/TiO2 materials. These analyses established correlations among Ir weight loading, electrode electrical conductivity, electrochemical stability, and Ir mass-based OER activity. The activated Ir@IrO(OH)x/TiO2 catalyst-support system demonstrated an exceptionally stable morphology of supported core-shell particles, suggesting strong catalyst-support interactions (CSIs) between nanoparticles and crystalline oxide facets. Operando XAS analysis revealed the reversible evolution of significantly contracted Ir-O bond motifs with enhanced covalent character, conducive to the formation of catalytically active electrophilic OI- ligand species. These findings indicate that atomic Ir surface dissolution generates Ir lattice vacancies, facilitating the emergence of electrophilic OI- species under OER conditions, while CSIs promote the reversible contraction of Ir-O distances, reforming electrophilic OI- and enhancing both catalytic activity and stability.

Bamboo-Like Carbon Nanotube-Encapsulated Fe2C Nanoparticles Activate Confined Fe2O3 Nanoclusters Via d-p-d Orbital Coupling for Alkaline Oxygen Evolution Reaction.

The efficient anion exchange membrane water electrolysis is challenging with low cell voltage and long-term stability at large current density, due to the unstable anodic oxygen evolution reaction (OER). Fe-based electrocatalysts are potential candidates for the anodic OER. In Fe-based materials, iron oxides always show better stability in alkaline solution but lower OER activity. However, the catalysts in previous study are difficult to continuously and effectively activate iron oxides supported on carbon during electrocatalysis. Herein, a new class of electrocatalyst: bamboo-like carbon nanotubes (B-CNT)-encapsulated Fe2C nanoparticles (NPs) supported Fe2O3 nanoclusters (NCs), named Fe2O3/B-CNT@Fe2C is reported. Theoretical calculations and experimental results reveal that B-CNT-encapsulate Fe2C NPs activate Fe2O3 NCs by the d-p-d orbital coupling, thereby weakening the adsorption of OOH* intermediate during OER process. The electrolyzer based on the electrocatalyst requires only 1.48 V to reach 1.0 A cm-2 and shows a long-term stability at 1.0 A cm-2 for 1600 h, comparable to the best-reported values for the anion exchange membrane water electrolyzer (AEMWE).

Cation Migration-Induced Lattice Oxygen Oxidation in Spinel Oxide for Superior Oxygen Evolution Reaction.

Activating the lattice oxygen can significantly improve the kinetics of oxygen evolution reaction (OER), however, it often results in reduced stability due to the bulk structure degradation. Here, we develop a spinel Fe0.3Co0.9Cr1.8O4 with active lattice oxygen by high-throughput methods, achieving high OER activity and stability, superior to the benchmark IrO2. The oxide exhibits an ultralow overpotential (190 mV at 10 mA cm-2) with outstanding stability for over 170 h at 100 mA cm-2. Soft X-ray absorption- and Raman-spectroscopies, combined with 18O isotope-labelling experiments, reveal that lattice oxygen activation is driven by Cr oxidation, which induces a cation migration from CrO6octahedrons toCrO4tetrahedrons. The geometry conversion creates accessible non-bonding oxygen states, crucial for lattice oxygen oxidation. Upon oxidation, peroxo O-O bond is formed and further stabilized by Cr6+ (CrO4 tetrahedra) via dimerization. This work establishes a new approach for designing efficient catalysts that feature active and stable lattice oxygen without compromising structural integrity.

Cation Migration‐Induced Lattice Oxygen Oxidation in Spinel Oxide for Superior Oxygen Evolution Reaction

Activating the lattice oxygen can significantly improve the kinetics of oxygen evolution reaction (OER), however, it often results in reduced stability due to the bulk structure degradation. Here, we develop a spinel Fe0.3Co0.9Cr1.8O4 with active lattice oxygen by high‐throughput methods, achieving high OER activity and stability, superior to the benchmark IrO2. The oxide exhibits an ultralow overpotential (190 mV at 10 mA cm–2) with outstanding stability for over 170 h at 100 mA cm–2. Soft X‐ray absorption‐ and Raman‐spectroscopies, combined with 18O isotope‐labelling experiments, reveal that lattice oxygen activation is driven by Cr oxidation, which induces a cation migration from CrO6 octahedrons to CrO4 tetrahedrons. The geometry conversion creates accessible non‐bonding oxygen states, crucial for lattice oxygen oxidation. Upon oxidation, peroxo O–O bond is formed and further stabilized by Cr6+ (CrO4 tetrahedra) via dimerization. This work establishes a new approach for designing efficient catalysts that feature active and stable lattice oxygen without compromising structural integrity.

Tracking Water Dissociation on RuO2(110) Using Atomic Force Microscopy and First-Principles Simulations.

The interaction between interfacial water and transition metal oxides is a primary enabling step for the oxygen evolution reaction (OER). RuO2 is a prototypical OER electrocatalyst whose ability to activate interfacial water molecules is essential to its OER activity. We image the dissociation of surface water into OH* and O* on RuO2(110), where * denotes adsorbed species, using atomic force microscopy. Starting from the surface-bound water molecules, which form a one-dimensional network along the rows of Ru surface sites, increasing the oxidative potential strips hydrogen away and transforms the water molecules into OH* and O*. This oxidative step changes the pattern of the adsorbates from one- to two-dimensional. First-principles calculations with interfacial polarization, capacitive charging, and adsorbate interactions attribute this evolution to the cooperative dehydrogenation of adsorbed water and OH* on RuO2. We use these results to map the surface phase diagram of RuO2(110) and provide a quantitative interpretation of its cyclic voltammetry. Our result provides the visualization of the water dissociation on a conductive oxide surface, a critical step in the OER, and demonstrates that the water activation is a collective phenomenon at RuO2(110) electrodes.

Enhancing Oxygen Reduction Reaction Electrocatalytic Performance of Nickel‐Nitrogen‐Carbon Catalysts through Coordination Environment Engineering†

Comprehensive SummarySingle‐atom catalysts (SACs) have attracted significant attention due to their high atomic utilization and tunable coordination environment. However, the catalytic mechanisms related to the active center and coordination environment remain unclear. In this study, we systematically investigated the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalytic activities of NiN4, NiN3, NiN3H2, NiN4X, NiN3X, and NiN3H2X (X denotes axial ligand) through density functional theory (DFT) calculations. This study unveils two distinct reaction pathways for ORR and OER, involving proton‐electron pairs adsorbed from both the solution and the catalyst surface. The overpotential is the key parameter to evaluate the catalytic performance when proton‐electron pairs are adsorbed from the solution. NiN3 and NiN3H2 show promise as pH‐universal bifunctional electrocatalysts for both ORR and OER. On the other hand, when proton‐electron pairs are adsorbed from the catalyst surface, the reaction energy barrier becomes the crucial metric for assessing catalytic activity. Our investigation reveals that NiN3H2 consistently exhibits optimal ORR activity across a wide pH range, regardless of the source of proton‐electron pair (solvent or catalyst surface).

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

AbstractHeterogeneous 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.

NiIr Nanowire Assembles as an Efficient Electrocatalyst Towards Oxygen Evolution Reaction in Both Acid and Alkaline Media.

Oxygen evolution reaction (OER) is the rate-limiting step in water electrolysis due to its sluggish kinetic, and it is challenging to develop an OER catalyst that could work efficiently in both acid and alkaline environment. Herein, NiIr nanowire assembles (NAs) with unique nanoflower morphology were prepared by a facile hydrothermal method. As a result, the NiIr NAs exhibited superior OER activity in both acid and alkaline media. Specifically, in 0.1 M HClO4, NiIr NAs presented a superior electrocatalytic performance with a low overpotential of merely 242 mV at 10 mA cm-2 and a Tafel slope of only 58.1 mV dec-1, surpassing that of commercial IrO2 and pure Ir NAs. And it achieved a significantly higher mass activity of 148.40 A/g at -1.5 V versus RHE. In 1.0 M KOH, NiIr NAs has an overpotential of 291 mV at 10 mA cm-2 and a Tafel slope of 42.1 mV dec-1. Such remarkable activity makes the NiIr NAs among the best of recently reported representative Ir-based OER electrocatalysts. Density functional theory (DFT) calculations confirmed alloying effect promotes surface bonding of NiIr with oxygen-containing reactants, resulting in excellent catalytic properties.

Strain Effects and Crystalline-Amorphous Interface of NiFe-LDH@S-NiFeOx/NF with Heterogeneous Structure for Enhancing Electrocatalytic Oxygen Evolution Reaction of Water-Electrolysis.

Electrochemical water-electrolysis for hydrogen generation often requires more energy due to the sluggish oxygen evolution reaction (OER). This work introduces a double-layered nanoflower catalyst, NiFe-LDH@S-NiFeOx/NF, featuring a crystalline NiFe-LDH coating on amorphous S-NiFeOx on nickel foam. Strategically integrating a crystalline-amorphous (c-a) heterostructure leverages strain engineering to enhance OER activity with low overpotentials (η100 = 220 and η500 = 245mV) and stability (135 h at η100 and 80 h at η500). Theoretical density functional theory (DFT) calculations reveal that the compressive strain can optimize the adsorption of oxygen-containing intermediates to reduce the reaction energy barrier, thus improving the reaction kinetics and performance of OER. Moreover, its phosphated derivative, NiFeP@S-NiFeOx/NF, exhibits high hydrogen evolution reaction (HER) performance (η10 = 64mV, η100 = 187mV). An alkaline water-electrolysis cell of NiFeP@S-NiFeOx/NF(-)||NiFe-LDH@S-NiFeOx/NF(+) requires only a cell voltage of 1.77V at 100 mA cm-2, demonstrating excellent stability over 110 h (at both 10 and 100mA cm-2). This work highlights the benefits of integrating crystal-amorphous interfaces and strain effects, offering insights into the understanding and optimizing catalytic OER mechanism and advancing water-electrolysis technology.

Modifying d–p orbital hybridization of Ni/Fe[sbnd]O species by high-valence ruthenium doping to enhance oxygen evolution performance

The electron distribution of catalysts can be modulated by high-valence metal doping, thus enhancing the intrinsic activity. Herein, we adopt Ru modification to adjust the d–p orbital hybridization of Ni-Fe oxyhydroxides, significantly increasing the oxygen evolution reaction (OER) activity. The amorphous NiFe0.5Ru0.1OxHy catalyst synthesized by sol–gel method exhibits excellent OER activity, far superior to commercial RuO2. In situ Raman and XPS results confirm that the NiOOH/FeOOH active species gradually form with increasing applied voltage. Density functional theory (DFT) calculations reveal that high-valence Ru dopants can effectively regulate the hybridization of d–p orbital of Ni/FeO, significantly increase the electron density around Fermi level, promote charge transfer, make them have more anti-bonding orbitals, enhance the binding ability of active sites to intermediates, reduce the reaction energy barrier of the rate-determining step (H2O → *OH), and thus improve the OER activity. In addition, NiFeRuOxHy as a cathode catalyst in a rechargeable zinc-air battery shows an outstanding cycle life of 600 h. This study provides a promising hybrid orbital method for designing high-performance OER catalysts for water splitting and rechargeable zinc-air batteries.

Influence of Annealing Temperature on the OER Activity of NiO(111) Nanosheets Prepared via Microwave and Solvothermal Synthesis Approaches.

Earth-abundant transition metal oxides are promising alternatives to precious metal oxides as electrocatalysts for the oxygen evolution reaction (OER) and are intensively investigated for alkaline water electrolysis. OER electrocatalysis, like most other catalytic reactions, is surface-initiated, and the catalyst performance is fundamentally determined by the surface properties. Most transition metal oxide catalysts show OER activities that depend on the predominantly exposed crystal facets/surface structure. Therefore, the design of synthetic strategies to obtain the most active crystal facets is of significant research interest. In this work, rock salt NiO OER catalysts with (111) predominantly exposed facets were synthesized by a solvothermal (ST) method either heated under supercritical or microwave-assisted (MW) conditions. Particular emphasis was placed on the influence of the post annealing temperature on the structural configuration and OER activity to compare their catalytic performances. The as-prepared electrocatalysts are pure α-Ni hydroxides which were converted to rock salt NiO (111) nanosheets with hexagonal pores after heat treatment at different temperatures. The OER activity of the electrodes has been evaluated in 0.1 M KOH using geometric and intrinsic current densities via normalization by the disk area and BET area, respectively. The lowest overpotential at a geometric current density of 10 mA/cm2 is found for samples pretreated by heating between 400 and 500 °C with a catalyst loading of 115 μg/cm2. Despite the very similar nature of the catalysts obtained from the two methods, the ST electrodes show a higher geometric and intrinsic current density for 500 °C pretreatment. The MW electrodes, however, achieve an optimal geometric current density for 400 °C pretreatment, while their intrinsic current density requires pretreatment over 600 °C. Interestingly, pretreated electrodes show consistently higher OER activity as compared to the poorly crystalline/less ordered hydroxide as-prepared electrocatalysts. Thus, our study highlights the importance of the synthesis method and pretreatment at an optimal temperature.

Wet sulfuration of molybdate and reconstruction regulation of trace Fe doping for oxygen evolution

There is a growing interest in the development of active, durable, and cost-effective electrocatalysts for oxygen evolution reactions (OER). In this study, we synthesized a self-reconstruction iron-doped sulfide-regulated nickel molybdate catalyst using wet chemical sulfuration and electrodeposition techniques. The core-shell nanorods (SC@NMO) were produced through rapid sulfuration. We investigated the effects of sulfur leaching on rapid and extensive electrochemical self-reconstruction. Our approach utilized the phase change of Fe3+ and electrodeposition-induced restructuring to enhance the catalyst's OER activity and stability in an alkaline electrolyte. Notably, iron ions establish a precipitation-dissolution dynamic equilibrium at the interface between the catalyst surface and the electrolyte, which minimizes iron loss and results in a more efficient and stable catalyst. The prepared sample, SC-Fe(Ni)OOH@NMO, demonstrated exceptional oxygen evolution performance and long-term stability in a 1 M KOH solution, achieving an overpotential of only 279 mV at a current density of 100 mA cm−2. It maintained stable operation for 200 h in a high-concentration 6 M KOH solution. The above data prove that this work provides a feasible strategy to enhance the OER catalytic capacity of metal oxides by the two modification methods of co-doping of metal and non-metal and reconstruction.

Synergy strategy of multi-metals confined in heteroatom framework toward constructing high-performance water oxidation electrocatalysts

The development of a low-cost, highly active, and non-precious metal catalyst for oxygen evolution reaction (OER) is of great significance. Multi-metallic catalysts containing Fe, Co, and Ni exhibit remarkable OER activity, while the specific contributions of each component and the synergistic effects in the ternary metal catalyst has remained elusive. In this work, we synthesized a series of S and N-doped mono-metallic, bi-metallic, and tri-metallic hollow carbon sphere electrocatalysts (M−SNC) with the goal of enhancing the catalysts OER activity and shedding light on the unique roles and synergistic effects of the various metals in the FeCoNi ternary metal catalyst. Our systematic analyses demonstrated the introduction of Fe effectively reduces the overpotential, Co accelerates the kinetics of OER, and the addition of Ni further improves the OER performance. Benefiting from the synergistic effects, the FeCoNi-SNC exhibits a low overpotential of 270 mV, with no morphological or structural changes after reaction, maintaining high activity for 72 h at 10 mA cm−2. Moreover, the assembled FeCoNi-SNC || Pt/C water electrolysis device operates for 65,000 s with minimal degradation, demonstrating its potential for practical application. This work presents a synergy strategy for the preparation of low-cost and highly efficient OER catalysts and further provides insights into the rational design and preparation of multicomponent catalysts.

Heterointerfacial engineering of N,P-doped carbon nanosheets supported Co/Co2P nanoparticles for boosting oxygen reduction and oxygen evolution reactions towards rechargeable Zn-air battery

Transition metal phosphides (TMPs) with high electrocatalytic activity for the oxygen evolution reaction (OER) are reckoned as a substitution of precious group metals catalysts in rechargeable Zn-air battery. In this work, Co/Co2P heterojunction nanoparticles supported N,P-doped carbon nanosheets (Co/Co2P@NPCNS) were designed and prepared via a facile one-step molten salt-assisted pyrolysis process. Density function theory calculations reveal that the heterogeneous interactions of Co/Co2P effectively enhance the bifunctional electrocatalytic activity for oxygen reduction reaction (ORR) and OER. The synergistic interaction between the Co/Co2P heterojunction nanoparticles with highly exposed active sites and excellent catalytic activity and the two-dimensional doped carbon nanosheets with high conductivity contributes to Co/Co2P@NPCNS exhibiting preeminent bifunctional ORR/OER activity and stability with a high half-wave potential for ORR (0.87 V), a low overpotential for OER (302 mV at 10 mA cm−2) and a low potential gap (0.66 V). The homemade rechargeable Zn-air battery performs high peak power density (187 mW cm−2) and exceptional endurance. This heterogeneous interface tactic of integrating TMPs with heteroatom-doped carbon materials may shed light on the research and development of non-precious metal electrocatalysts.