Enhanced Oxygen Evolution Research Articles

Enhancing oxygen evolution reaction of CoP nanosheets via interfacial engineering with CoFe-LDH nanosheets

Recently, transition-metal phosphides have emerged as favorable electrocatalysts for facilitating oxygen evolution reactions (OERs). This study successfully synthesized a heterostructure comprising interconnected ultrathin nanosheet arrays of CoxP grown on nickel foam (NF) through electrodeposition and phosphorization processes. Subsequently, a layer of CoFe layered double hydroxides (LDH) was electrodeposited onto the CoxP/NF substrate, resulting in the formation of the heterostructure CoxP@CoFe-LDH. The OER efficiency of the CoxP nanosheets exhibited substantial improvement because of the more accessible active sites and faster electron transfer capability of the heterostructure system. This improvement can be attributed to the higher surface area and well-established interfacial coupling between the ultrathin nanosheets of CoxP and CoFe-LDH. Consequently, the CoxP6@CoFe2/NF anode displays remarkable performance in enabling OERs, requiring merely a minimal overpotential of 230 mV at a current density of 10 mA·cm−2 in 1 M KOH. This result signifies a substantial improvement when compared to the performance of the bare CoxP and CoFe-LDH samples. Moreover, the heterostructure system enhanced the structural durability during the OERs, leading to remarkable stability over a continuous operation period of 50 h.

Ultrafast room-temperature construction of hierarchical hollow rodlike nanoarrays based on amorphous NiFeCo layered double hydroxide toward enhanced oxygen evolution reaction

Designing and constructing non-noble metal electrocatalysts with high catalytic activity for oxygen evolution reaction (OER) is a significant challenge for energy storage and conversion. Transition-metal-based layered double hydroxides (LDHs) are the most efficient OER catalysts. However, their catalytic performance and commercial application are limited by their small electrochemical active areas and poor electronic conductivity. Herein, hollow hierarchical rodlike nanoarrays on nickel foam assembled with amorphous NiFeCo-LDH nanosheets were prepared using a metal–organic framework, ZIF-67, as a sacrificial template by a facile and ultrafast ion-exchanged reaction at room temperature. The as-prepared electrocatalyst possessed a large specific surface area (397 m2/g), unique structure, fast charge transfer and abundant active sites, and thus displayed a superior performance for OER with a low overpotential of 202 mV at 10 mA/cm2, a Tafel slope of 47.9 mV/dec and long-term durability in 1.0 M KOH electrolyte. This research affords a facile strategy to rationally design high activity electrocatalysts of multi-metallic LDHs for OER.

Bi-functional CoCr2O4 hollow-sphere for enhanced oxygen evolution reaction and photocatalyst for harmful environmental pollutants removal

The development of a high-performance, cost-effective, and durable multifunctional semiconductor is crucial for clean energy and environmental remediation applications such as oxygen evolution reaction (OER) and photocatalysts. In this research, we have developed a hollow sphere-based spinel-structured CoCr2O4 (HS.CCO) for bi-functional applications. These hollow spheres exhibit excellent electrocatalytic OER performance under an alkaline (1 M potassium hydroxide (KOH)) medium, which displays a higher electrocatalytic ability. The spinel hollow spheres demonstrate favorable overpotentials and Tafel potentials of 180 mV and 162 mV/dec, respectively towards OER activity. On the other hand, as a photocatalysis, they portrayed outstanding degradation efficiency under visible light irradiation towards Congo red (CR) dye degradation. Within the short treatment time higher CR degradation efficiency is achieved. These photo-electroactive spinel hollow spheres accelerate efficient OER and visible-light-driven photocatalysis with remarkable stability. They serve as an excellent example of a multifunctional heterogeneous catalyst. Finally, the obtained results indicate the current needs and future demands for enhancing the prospects of multifunctional semiconductor catalysts.

Fabrication and characterization of Nickel-coated 3D printed electrodes for enhanced oxygen evolution reaction in acidic media at various temperatures

Additive manufacturing (AM), often referred to as 3D printing, is a new technology that allows objects to be created by adding layer by layer, as opposed to traditional manufacturing processes. Therefore, the rapid and cost-effective AM method can facilitate research and development efforts in the field of electrochemistry. In this study, oxygen evolution reaction (OER) electrodes are fabricated by a 3D printing technique utilizing carbon-based (PP filament) and graphene-based PLA filaments (BM filament). Electrodes are then coated with Ni by electrochemical deposition method at different temperatures. Electrochemical analysis of Ni coated PP and BM electrodes is made in acidic environments (0.5 M H2SO4) using different characterization techniques. The results indicate that PP/Ni-50 and BM/Ni-50 electrodes have the highest catalytic activity for OER in acidic media. PP/Ni-50 and BM/Ni-50 electrodes exhibited a superior double layer (Cdl) value than other Ni coated 3D printed electrode samples, and their active surface areas are calculated as 0.201 cm2 and 0.286 cm2, respectively. A larger active surface area leads to an increase in the number of active sites, causing the OER process to be more effective. Consequently, increasing the active surface area of electrode samples is crucial for improving the efficiency and effectiveness of the Oxygen Evolution Reaction (OER) process, especially in the context of renewable energy and sustainable technology applications.

A theoretical study on the enhanced oxygen evolution performance of NiN4-graphene by Ni nanoclusters

Isolated metal-coordinated nitrogen embedded carbon (M–N–C) materials are potential alternatives to noble catalysts for oxygen evolution reaction (OER), and the activity of metal centers can be further modulated by adjusting the coordination environment. Recently, experimental studies have shown that the aggregation of metal atoms into small clusters or particles is inevitable during the high temperature pyrolysis, while the influences of metal clusters on the OER activity of single metal atoms in M–N–C are unclear. Herein, taking Ni-based single atom as examples, the interaction characters of NiN4 doped graphene (NiN4-graphene) with different Ni clusters were studied. The modulation effects of Ni clusters to the NiN4-graphene were systematically investigated from the geometric configurations, electronic structures, and the OER activity of the Ni single atom. It was found that the OER performance of NiN4-graphene can be remarkably improved through the addition of Ni clusters, and the lowest overpotential of 0.43 V is achieved on NiN4-graphene with the modification of Ni13 cluster, which is smaller than that of 0.69 V on NiN4-graphene. Electronic properties calculations showed that the charge transfer from Ni clusters to NiN4-graphene will alter the density of states of Ni single atom near the Fermi level, which promotes the charge transfer from NiN4-graphene to oxygen containing products and optimizes the adsorption strength of oxygen intermediate to close to the ideal adsorption free energy of 2.46 eV by enhancing the hybridization interaction between the O-p orbitals and the Ni-dxz , Ni-dyz orbitals, and finally leading to an enhanced OER activity. The current findings highlight the important role of metal clusters on improving the catalytic performance of M–N–C materials, which benefits for the rational design of M–N–C catalysts with high catalytic activity.

Sulfate anchored on the defective NiO by ion irradiation realizes enhanced oxygen evolution reaction

NiO has attracted wide attention in the past decade as a cost-effective electrochemical catalyst for OER. However, its relatively poor performance and conductivity limit its commercial applications. Here, we highlight a unique ion irradiation method to enhance the catalytic activity of NiO. Benefiting from sulfate anchoring and the introduction of oxygen vacancies by He+ ion irradiation, the optimal catalyst (ir-S-NiO) exhibits an outstanding OER performance with a low overpotential of 269 mV at 10 mA cm−2. Moreover, the fabricated Anion exchange membrane water electrolyzer (AEMWE) constructed by the ir-S-NiO is demonstrated to need a cell voltage of 1.72 V to reach a current density of 0.1 A cm−2 and shows remarkably long-term stability for 200 h without obvious attenuation at the current density of 0.5 A cm−2. This work provides a new method for the development of high-performance and stable OER electrocatalysts.

Regulating Excess Electrons in Reducible Metal Oxides for Enhanced Oxygen Evolution Reaction Activity: A Mini-Review.

Identifying a universal activity descriptor for metal oxides, akin to the d-band center for transition metals, remains a significant challenge in catalyst design, largely due to the intricate electronic structures of metal oxides. This review highlights a major advancement in formulating the number of excess electrons (NEE) as an activity descriptor for oxygen evolution reaction (OER) on reducible metal oxide surfaces. We elaborate on the quantitative relationship between NEE and the adsorption properties of OER intermediates, and unveil the decisive role of the octet rule on the OER performance of these oxides. This insight provides a robust theoretical basis for designing effective OER catalysts. Moreover, we discuss critical experimental evidence supporting this theory and summarize recent advances in employing NEE as a guiding principle for developing highly efficient OER catalysts experimentally.

Nanostructured Co3O4@NiFe-LDH heterojunction catalysts for improving oxygen evolution reaction in alkaline environment

Constructing nano-heterojunction catalysts is a highly efficient method for enhancing the thermodynamics and kinetics towards oxygen evolution reaction. In the present study, NiFe-LDH nanoparticles in-situ grown on Co3O4 nanowires bring about abundant heterogeneous interfaces, which productively increase specific surface area and tune electron density distribution. The as-obtained composite comprises rich unsaturated Co sites on Co3O4 and hybrid crystalline/amorphous NiFe-LDH phase, both of which expedite the flow of charge and expose large amounts of active sites. The Co-Ni-Fe electron transport channels are established at the core-shell heterojunction with the transmission of electrons from Co3O4 to NiFe-LDH. The resultant optimal Co3O4 @NiFe-LDH/NF-100 catalyst displayed attractive OER activity with low overpotential of 270 mV at 50 mA cm−2, along with excellent durability in alkaline media. This typical core-shell heterojunction promotes H2O dissociation and strengthens the adsorption of intermediates, thereby enhancing oxygen evolution reaction.

The photoelectrochemically enhanced oxygen evolution reaction via thin films of novel (1:2:1) SnO-Mn2O3-TiO2 hybrid nanotubes

The oxygen and hydrogen evolution reactions play a significant role in overall water splitting. The photoelectrochemical water splitting offers a high potential for conversion efficiency at low voltage and temperature. Therefore, in the present work comparative studies of novel (1:2:1)) SnO-Mn2O3-TiO2 (SMT) ternary and SnO-Mn2O3 (SM), SnO-TiO2 (ST) and Mn2O3-TiO2 (MT) binary mixed-metal oxides thin films for hydrogen generation are performed. method. The Aerosol Assisted Chemical Vapor Deposition (AACVD) fabricated thin films were analyzed through X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron microscopy (XPS) and UV–visible spectroscopy to determine the crystallinity, surface morphology, binding energy, and band gaps. The Photoelectrochemical studies demonstrate that the SnO-Mn2O3-TiO2 (SMT) thin film yields 1.96, 2.37, and 2.7 times maximum current density than the binary SnO-Mn2O3 (SM), SnO-TiO2 (ST) and Mn2O3-TiO2 (MT) metal oxides, respectively. These results illustrate that due to unique topography, uniform distribution, and good optoelectronic properties of ternary SnO-Mn2O3-TiO2 (SMT) nanotubular layers show better light-harvesting performance as compared to the binary (SM, ST, and MT) metal oxides. Therefore, it is believed that SMT is a promising candidate for energy harvesting applications.

Stable 1T-MoS2 by Facile Phase Transition Synthesis for Efficient Electrocatalytic Oxygen Evolution Reaction.

The 1T phase of MoS2 exhibits much higher electrocatalytic activity and better stability than the 2H phase. However, the harsh conditions of 1T phase synthesis remain a significant challenge for various extensions and applications of MoS2. In this work, a simple hydrothermal-based synthesis method for the phase transition of MoS2 is being developed. For this, the NH2-MIL-125(Ti) (Ti MOF) is successfully utilized to induce the phase transition of MoS2 from 2H to 1T, achieving a high conversion ratio of ≈78.3%. The optimum phase-induced MoS2/Ti MOF heterostructure demonstrates enhanced oxygen evolution reaction (OER) performance, showing an overpotential of 290mV at a current density of 10mA cm-2. The density functional theory (DFT) calculations are demonstrating the benefits of this phase transition, determining the electronic properties and OER performance of MoS2.

Regulating the Electronic Structure of Metal-Organic Frameworks by Introducing Mn for Enhanced Oxygen Evolution Activity.

The construction of low-cost and highly efficient oxygen evolution electrocatalysts is paramount for clean and sustainable hydrogen energy. In recent years, metal-organic framework (MOF) OER electrocatalysts have attracted tremendous research attention. Herein, we report a simple and facile strategy to construct bimetallic MOFs (named CoMn0.01) for enhancing OER catalytic performance. Significantly, CoMn0.01 exhibited remarkable OER activity (255 mV at 10 mA cm-2) and a low Tafel slope of 66 mV dec-1, superior to those of commercial benchmark electrocatalysts (RuO2, 352 mV, 178 mV dec-1). Besides, the catalyst demonstrated outstanding longevity for 144 h at a current density of 100 mA cm -2. Mn doping can regulate the electronic structure of Co MOFs, which optimizes charge transfer capability and improves conductivity.

Lowering the Coordination of Octahedra in Spinel Oxides by the Robust Fe–N Bonds for Enhancing Oxygen Evolution Reaction

Lowering the Coordination of Octahedra in Spinel Oxides by the Robust Fe–N Bonds for Enhancing Oxygen Evolution Reaction

Surface Reconstruction of Co‐based Catalysts for Enhanced Oxygen Evolution Activity in Anion Exchange Membrane Water Electrolysis

AbstractDeveloping high‐performance and durable electrocatalysts for the oxygen evolution reaction (OER) is of utmost importance for green hydrogen production via anion exchange membrane water electrolysis (AEMWE). Herein, it is presented that a straightforward surface reconstruction strategy for preparing a robust Co‐based OER catalyst with increased mass transfer activity while preserving the active CoOOH phase during the OER. This strategy comprises electrochemical oxidation of electrodeposited Co‐based catalysts prior to heat treatment, allowing for the meticulous control of the oxidation potential to optimize the OER activity. The optimized catalyst exhibits an overpotential of 190 mV at 10 mA cm−2 and a Tafel slope of 32.7 mV dec−1 under half‐cell conditions. In an AEMWE single‐cell system, it shows a current density of 1590 mA cm−2 at 1.8 V and 60 °C and demonstrates a degradation rate of 0.2 mV h−1 during 1000 h of operation at 500 mA cm−2. This study not only provides a simple yet potent strategy to enhance the OER activity but also offers insights regarding the factors enhancing the OER performance.

Multi metallic electro-catalyst design for enhanced oxygen evolution reaction: Immobilizing MnFe nanoparticles on ZIF-67-decorated graphene oxide

The advancement of large-scale hydrogen production and its application via electrocatalytic water splitting heavily relies on progress in developing highly active inexpensive, and efficient electrocatalysts for oxygen evolution reactions (OER), which continues to pose a significant challenge. Herein, we prepare GO@ZIF-67@MnFe with embedded iron (Fe) and manganese (Mn) nanoparticles on graphene oxide (GO) decorated with a zeolitic imidazolate framework (ZIF-67) using a facile and cost-effective method. The as-prepared GO@ZIF-67@MnFe catalyst exhibits remarkable electrocatalytic activity with a low overpotential of only 236 mV at the current density of 10 mA cm–2, a small Tafel slope of 55.7 mV dec–1, and robust durability in 1.0 M KOH electrolyte. Additionally, we conduct a systematic study to investigate the electrocatalytic OER activity of ZIF-67, ZIF-67@Mn, ZIF-67@Fe, and ZIF-67@MnFe using density functional theory (DFT) calculations. The experimental and DFT calculation results suggest that the introduction of Fe and Mn to ZIF-67 improves OER performance by reducing the activation energy barrier and accelerating kinetics. This study presents a promising strategy and rational design methodology for the developing multi-metallic catalysts utilizing ZIF derivatives for water splitting.

The catalytic activity of reduced graphene aerogel anchored with CoFe2O4 spinel via self-assembly technique for enhanced oxygen evolution reaction

The development of low-cost and highly active oxygen evolution reaction (OER) electrocatalysts is of significant importance for the advancement of sustainable new clean energy and storage systems. Herein, reduced graphene oxide (rGO) anchored with spinel CoFe2O4 (rGO/CoFe2O4) is prepared by hydrothermal synthesis, combined with freeze-drying and heat treatment processes. The effects of different spinel types, the loading amount of CoFe2O4 and heat treatment temperatures on the OER performance are investigated. The resulting possesses a typical mesoporous structure composed of CoFe2O4 nanoparticles with 20–50 nm and the lamellar rGO, leading to a large BET specific surface area. The as-prepared rGO/CoFe2O4 has an overpotential of 325 mV, a low Tafel slope (63.02 mV/dec) at a current density of 10 mA cm−2, and shows excellent stability with no significant current decay. Based on Density Functional Theory (DFT) calculations, the transition from *O to *OOH has the highest Gibbs free energy, which is the rate-determining step of the entire catalytic process. The Fe site on the (100) crystal plane of CoFe2O4 is most likely the reactive site for the OER process, improving the OER activity by decreasing the binding strength between the catalytic surface and adsorbed *O intermediates.

Supramolecular Macrocycle Regulated Single‐Atom MoS2@Co Catalysts for Enhanced Oxygen Evolution Reaction

The development of active water oxidation catalysts for water splitting has stimulated considerable interest. Herein, the design and building of single atom Co sites using a supramolecular tailoring strategy are reported, that is, the introduction of pillar[4]arene[1]quinone (P4A1Q) permits mononuclear Co species stereoelectronically assembled on MoS2 matrix to construct an atomically dispersed MoS2@Co catalyst with modulated local electronic structure, definite chemical environment and enhanced oxygen evolution reaction performance. Theoretical calculations indicate that immsobilized single‐Co sites exhibit an optimized adsorption capability of oxygen‐containing intermediates, endowing the catalyst an excellent electrocatalytic oxygen evolution reaction activity, with a low overpotential of 370 mV at 10 mA cm−2 and a small Tafel slope of 90 mV dec−1. The extendable potential of this strategy to other electrocatalysts such as MoS2@Ni and MoS2@Zn, and other applications such as the hydrogen evolution reaction was also demonstrated. This study affords new insights into the rational design of single metal atom systems with enhanced electrocatalytic performance.

Enhanced oxygen evolution reaction in hierarchical NiFe/NiO electrocatalysts: Effects of electrodeposition condition on electrode

This study fabricated an OER electrocatalyst with a hierarchical structure by electrodepositing Ni-Fe on NiO. The prepared electrocatalyst exhibited high activity and stability. Furthermore, the OER characteristics of the NiFe/NiO electrode were investigated by changing the metal (Ni and Fe) concentration and Ni:Fe ratio in the plating bath. As the plating bath concentration decreased, NiFe-layered double hydroxide was prominently formed due to an increase in local pH. The electrode obtained using a relatively low plating bath concentration of 130 mM demonstrated high activity with an overpotential of 245 mV and Tafel slope of 27.6 mV dec-1 at a current density of 10 mA/cm2. When the Ni:Fe ratio in the plating bath was adjusted, OER activity increased as the Fe content of the electrode increased to approximately 20.9 at.%, and as the Fe content increased beyond that, the activity gradually decreased. Fe inhibits Ni oxidation and acts as an active site owing to Fe3+ substitution in the γ-NiOOH structure, resulting in increased OER activity. However, when the Fe content was > 29 at.%, the inactive phase γ-FeOOH predominantly grew and the OER activity decreased.

Origin of Spin‐State Precise Modulation for Enhanced Oxygen Evolution Activity: Effect of Secondary Coordination Sphere

AbstractThe process of oxygen evolution reaction (OER) is crucial for energy storage and conversion, and the spin electronic structure of catalyst significantly influences its catalytic activity. Precisely regulating the spin electronic structures of metal active centers with intermediate spin (IS) states is challenging but important. This study presents a general method for achieving spin‐state precise modulation by altering the secondary coordination sphere (SCS) in Fe‐substituted LaCo1‐xFexO3 perovskites, denoted as Co6‐y−[Co]−Fey (y = 0–6). The concentration‐dependent SCSs can precisely regulate the spin state of Co3+ from high‐spin (HS) to IS and low‐spin (LS) state by tuning the Co─O binding energy of primary coordination sphere (PCS) to ≈567 KJ mol−1. The binding energy demonstrates a strong negative correlation with the spin state of Co3+, serving as a quantitative descriptor for precise spin‐state modulation. Furthermore, a universal optimal doping concentration is proposed for generating IS‐state Co3+ with the best OER activity, ranging from 1/(m+1) to 2/(m+1) in M‐doped ACo1‐xMxOy system with the coordination number of m. As a proof‐of‐concept, the LaCo7/9Fe2/9O3 with IS Co3+ exhibits significantly enhanced OER activity, almost six times higher than the control samples (without IS Co3+). These findings provide new insights into spin‐state modulation for effective OER catalysts.

Engineered oxidation states in NiCo2O4@CeO2 nanourchin architectures with abundant oxygen vacancies for enhanced oxygen evolution reaction performance

Sluggish oxygen evolution reaction (OER) as the half reaction of water electrolysis hindered the production of clean hydrogen, necessitates a cost-effective electrocatalyst. Spinel nickel cobaltite (NiCo2O4), characterized by its lower cost, flexibility in oxidation states of cations, and stable spinel structure, holds promise as an OER electrocatalyst. However, there is still room for improvement in terms of its intrinsic electrochemical activity, conductivity, and active surface area. Inspired by the flexible valence states of Ni and Co, in this study, CeO2 was introduced into NiCo2O4 for further electronic structure adjustment. The result was the synthesis of an urchin-like NiCo2O4@CeO2 (NCOC), and the elucidation of its formation mechanisms, expressed conclusively through reaction formulas. NCOC, characterized by an open architecture and a rough surface, ensures rapid mass transportation and charge diffusion. Within NCOC, numerous oxophilic Ce3+ sites with oxygen vacancies construct electron transport pathways, accelerating charge-transfer. This simultaneously induces an increase in the oxidation states and proportions of Ni3+ and Co3+ in NCOC, reinforcing the covalence of Ni–O and Co–O bonds, expediting the ad/desorption of intermediates during OER. The electronic structure variations of NCOC were further verified through density functional theory (DFT) analyses, revealing alterations in adsorption configurations of intermediates and a decrease in adsorption free energies for intermediates on NCOC during OER. In practical terms, NCOC demonstrated a low overpotential of 228 mV at a current density of 10 mA cm−2 under 1 M KOH, maintaining long-term electrochemical stability for 100 h. Overall, this study provides a universal approach for designing highly cost-efficient electrocatalysts for OER.

Tungsten-doped cobalt-iron bimetallic phosphide nanoparticles for enhanced oxygen evolution reaction

BackgroundHydrogen obtained from electrochemical water splitting is an efficient method for hydrogen production, which is urgent to develop high efficiency electrocatalyst and commercialize the process. MethodsIn our work, we used coprecipitation, doping and phosphating strategies to report the trimetallic Prussian blue analogue precursors (W-CoFe PBA) were prepared by doping sodium tungstate into cobalt-iron-Prussian blue analogues (CoFe PBA), and then by a low temperature phosphating treatment to obtain tungsten doped cobalt-iron phosphide (W-CoP/FeP) heterostructures. This strategy of doping and then phosphating can allow the charge distribution is adjusted, the conductivity is increased, the electron transport to the surface is accelerated, and the synergistic effect between CoP and FeP is enhanced. Significant findingsThe experimental results show that the mass ratio of tungsten source to CoFe-PBA is 0.5 (0.5W-CoP/FeP), which shows outstanding activity with overpotentials of 282 mV for the oxygen evolution reaction (OER) in 1 M KOH at a current density of 10 mA cm−2 and Tafel slope of 29.14 mV dec−1. Simultaneously, it also exhibits excellent stability for 24 h in the chronopotentiometry test. This work provides a simple improvement for the application of Prussian blue analogues in the electrochemical water splitting.