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Purposes It is of great significance for the storage and utilization of solar energy to develop high-efficiency non-precious metal oxygen evolution reaction (OER) catalysts that can be used in water splitting under near-neutral conditions. Methods FeOOH@Ni-Bi/NF electrocatalyst was constructed in two steps by electro-oxidation treatment and electro-deposition of Ni(OH)2/NF that obtained by hydrothermal method. Findings The large number of active sites provided by nickel foam (NF) substrate and three-dimensional nanosheet array structure of the catalyst facilitate the mass transfer process of OER. In addition, the electrochemical activity of catalyst is greatly enhanced by modulating the electro-oxidation degree of Ni-Bi and the amount of deposited FeOOH. Catalytic performance of the optimized FeOOH@Ni-Bi/NF is tested in near-neutral medium (0.1 mmol/L K2B4O7) with an overpotential of 394 mV and a Tafel slope of 54.2 mV/dec at 20 mA/cm2, showing excellent catalytic activity and long-term stability for OER.

Herein, we report an easily oxidized Co–Fe perovskite fluoride as an efficient catalyst for the oxygen evolution reaction (OER). In situ Raman spectroscopy showed that the presence of F promotes reconstruction to form highly active (Co3+Fe3+)OOH, and the current density of 10 mA cm−2 can be achieved at the overpotential of only 118 mV in 1 M KOH aqueous solution. This work helps to understand the role of fluoride during the OER. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 to produce valuable multi‐carbon products is a promising avenue for promoting CO2 conversion and achieving renewable energy storage, and it has also attracted considerable attention recently. However, the synthesis of Cu electrode with a controllable electrochemical active surface area (ECSA) to understand its role in CO2 reduction to C2H4 remains challenging. Herein, a series of Cu electrodes with different ECSA is synthesized through a simple oxidation‐reduction approach. We reveal that the improved selectivity of C2H4 is proportional to the ECSA of Cu in the low ECSA range, and a further increase in ECSA has a negligible effect on its selectivity. The enlarged surface area could strengthen the local pH effect near the surface of Cu electrode and suppress the generation of C1 products as well as H2. The study provides a feasible strategy to rationally design electrocatalysts with high electrochemical CO2 reduction performances. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is crucial for hydrogen production. However, OER with four‐electron transfer requires electrocatalysts to speed up its sluggish kinetics in alkaline solutions. Herein, amorphous CoV phosphate (denoted as CoV−Pi) nanosheets synthesized by a straightforward one‐step hydrothermal approach is reported, which provide a low overpotential of 320 mV at 10 mA cm−2, a small Tafel slope down to 48.8 mV dec−1 and long‐term durability over 80 h. The efficient activity is ascribed to the amorphous nanosheets structure, high electrochemically active surface area, enhanced surface wettability and the synergistic effect of the active metal atoms. This study significantly indicates that CoV−Pi is a promising alternative to replace expensive noble metal‐based catalysts for electrochemical water splitting. [ABSTRACT FROM AUTHOR]

Although metal‐organic frameworks have proven to be excellent electrocatalytic materials, their application as electrode materials remains limited. The preparation of heterostructures is considered an effective method to improve catalytic activity. Herein, we describe the design and assembly of a dual‐MOF heterostructure (CoNi−ZIF‐67@Fe−MIL‐100, denoted ZIF@MIL). Specifically, we grew a layer of MIL‐100 in situ on a bimetallic ZIF‐67 surface using a solvothermal method. We demonstrate that the ZIF@MIL has remarkable OER electrocatalytic performance, requiring a low overpotential and showing a small Tafel slope, compared to pure ZIF‐67 and MIL‐100 in 1.0 m KOH. More importantly, it has excellent operational durability for 50 h at 100 mA cm−2. The high catalytic activity of ZIF@MIL can be attributed to the heterostructure that can expose more active sites, the synergistic effect between ZIF‐67 and MIL‐100, and improvement of electron transfer ability. Our work provides a new way to design and prepare dual‐MOF crystals with different structures as electrocatalysts. [ABSTRACT FROM AUTHOR]

Electrochemical hydrogen production through water splitting is one of the most promising methods for the storage and utilization of renewable energy. However, it is hindered by the sluggish oxygen evolution reaction (OER). Therefore, there is an urgent need to develop an efficient and robust OER catalyst through a simple and low-cost method. Herein, we report the in situ fabrication of amorphous Fe–NiSe/NF without a polymeric binder as a three-dimensional (3D) nanowire electrode for efficient water oxidation. It shows good durability in 1 M KOH. This catalyst requires overpotentials of only 233 and 275 mV to drive current densities of 10 and 100 mA cm−2, and it shows a low Tafel slope of 48 mV dec−1. The faradaic efficiency of Fe–NiSe/NF for oxygen evolution was determined to be close to 96.8%. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 to produce valuable multi‐carbon products is a promising avenue for promoting CO2 conversion and achieving renewable energy storage, and it has also attracted considerable attention recently. However, the synthesis of Cu electrode with a controllable electrochemical active surface area (ECSA) to understand its role in CO2 reduction to C2H4 remains challenging. Herein, a series of Cu electrodes with different ECSA is synthesized through a simple oxidation‐reduction approach. We reveal that the improved selectivity of C2H4 is proportional to the ECSA of Cu in the low ECSA range, and a further increase in ECSA has a negligible effect on its selectivity. The enlarged surface area could strengthen the local pH effect near the surface of Cu electrode and suppress the generation of C1 products as well as H2. The study provides a feasible strategy to rationally design electrocatalysts with high electrochemical CO2 reduction performances. [ABSTRACT FROM AUTHOR]

In this paper we synthesized a crystalline Ag-C i oxygen-evolution catalyst with an entirely new composition and structure in situ in a carbonate solution (pH = 8.3) with Ag+ at 70 °C. We studied the factors that influenced the synthesis of the oxygen-evolution catalyst (electrolyte environment temperature, silver ion concentration, concentration of carbonates) under mild conditions. The structure, morphology, composition, and catalytic activity of Ag-C i catalyst were analyzed using techniques such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical measurements. Our results showed that the diffraction peaks of the Ag-C i catalysts synthesized at 70 °C were consistent with the AgO phase and that the catalytic composition of the Ag-C i catalyst was the AgⅠO/AgⅡO redox couple. The oxygen-evolution rate of the catalyst synthesized in a carbonate solution (pH = 8.3) at 70 °C was 50 times higher than that synthesized at 5 °C (18.3 μmol h−1); additionally, its oxygen evolution overpotential decreased to 246.7 mV. The electrolyte solution and Ag+ ion concentration greatly impacted the catalytic activity of the Ag-C i catalyst for water splitting. [ABSTRACT FROM AUTHOR]

Abstract: A weakly acidic H3BO3 solution (pH = 5.1) was used to synthesize new oxygen-evolution catalysts for water splitting under mild conditions. Two novel oxygen-evolution catalysts, Co–BA i and Mn–BA i (BA i = inorganic boric acid), were obtained in the H3BO3 solution with added Co2+ and Mn2+, respectively. The average oxygen evolution rate in the H3BO3 solution with Co2+ was 0.3133 μmol/h, about 70 times greater than the rate without a metal ion; the rate with Mn2+ was 1.13 μmol/h, about 250 times greater. The phases, morphologies, and compositions of the Co–BA i and Mn–BA i catalysts were analysed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. [Copyright &y& Elsevier]

NiFe-layered double hydroxide (NiFe–OH) is one of the most promising candidate materials for the oxygen evolution reaction (OER) in an alkaline electrolyte. However, it is difficult to be oxidized into Ni3+FeOOH active species with high valence Ni under mild conditions; thus, the activity under mild conditions is inferior. We report here that NiFe–OH is converted to amorphous NiFeO x H y (a3-NiFe-OH) with easily oxidized electron-deficient Ni2+ after pre-oxidation in an alkaline solution boosts the OER performance under mild conditions. The amorphous structure of a3-NiFe-OH also enlarges the electrochemically active area to expose more active sites. It merely needs an overpotential of 350 mV at 10 mA cm−2 in 0.1 M KHCO 3 electrolyte. The corresponding Tafel slope is as low as 89 mV dec−1. This work affords a strategy for developing (near) neutral OER catalysts. [Display omitted] • NiFeO x H y with electron-deficient Ni2+ and amorphous structure was prepared. • The electron-deficient Ni2+ can easily be oxidized during oxygen evolution reaction. • The amorphous structure helps to expose more active sites. • NiFeO x H y exhibits enhanced oxygen evolution reaction activity in mild condition. [ABSTRACT FROM AUTHOR]

Ruthenium oxide (RuO 2 ) is considered one of the most promising catalysts for replacing iridium oxide (IrO 2 ) in the acidic oxygen evolution reaction (OER). Nevertheless, the performance of RuO 2 remains unacceptable due to the dissolution of Ru and the lack of *OH in acidic environments. This paper reports a grain boundary (GB)-rich porous RuO 2 electrocatalyst for the efficient and stable acidic OER. The involvement of GB regulates the valence state of Ru and weakens the interaction between Ru and O, effectively facilitating *OH adsorption and *OOH formation. Notably, achieved a record-high catalytic activity (145 mV at 10 mA cm -2 ) with a low Tafel slope (40.9 mV dec -1 ) and a remarkable mass activity of 332 mA mg -1 Ru at 1.5 V versus reversible hydrogen electrode is achieved. Additionally, the porous RuO 2 exhibits superb stability with an ultra-low degradation rate of 26 µV h -1 over a 50-day durability test. This study opens a viable pathway for the development of efficient and robust Ru-based acidic OER electrocatalysts., (© 2024 Wiley‐VCH GmbH.)

Herein, we report an easily oxidized Co-Fe perovskite fluoride as an efficient catalyst for the oxygen evolution reaction (OER). In situ Raman spectroscopy showed that the presence of F promotes reconstruction to form highly active (Co 3+ Fe 3+ )OOH, and the current density of 10 mA cm -2 can be achieved at the overpotential of only 118 mV in 1 M KOH aqueous solution. This work helps to understand the role of fluoride during the OER.