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Due to the slow reaction kinetics of the oxygen evolution reaction (OER), the electrolysis rate of water is greatly limited. Therefore, it is of great significance to study stable and efficient non-noble metal based electrocatalysts. In this paper, three-dimensional (3D) spherical V-NiFe LDH@Ni3S2 was developed by exquisitely decorating ultra-thin V-doped NiFe layered dihydroxide (NiFe-LDH) on Ni3S2 nanosheets supported by nickel foam (NF). It is worth mentioning that V-NiFe LDH@Ni3S2 exhibits an excellent electrocatalytic performance and only 178 mV overpotential is required in 1 M KOH to achieve a current density of 10 mA cm−2. Long-term chronoamperometry manifests its superior electrochemical stability. The combination of NiFe LDH and conductive substrate coupling can drastically afford abundant active sites and accelerate charge transfer, and V doping can markedly regulate the electronic structure. Therefore, the activity and durability of the electrocatalysts are greatly improved. This study may provide a new strategy for the preparation of efficient OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Since the complicated multiple electron transfer process and slow kinetics in the OER process seriously hinder the electrochemical decomposition of water, it is urgent to design and develop electrocatalysts with excellent performance and superior stability to reduce overpotential and accelerate the reaction dynamics of the OER. Herein, a unique ultra-thin nanosheet bimetal electrocatalyst NiFe-MOF/IF was synthesized by a one-step hydrothermal method, and characterized by SEM, XRD, TEM, and XPS. NiFe-MOF/IF shows superior OER electrocatalytic activity in 1 M KOH electrolyte solution, and an ultralow overpotential of only 230 and 262 mV was required to achieve a current density of 10 and 100 mA cm−2, respectively, with a relatively small Tafel slope of 30.46 mV dec−1 for the OER. No obvious degradation of the current density at 10 mA cm−2 was observed over about 16 h, which indicates the excellent stability of the catalyst. Favourable activity and benign durability of NiFe-MOF/IF can be attributed to the three-dimensional high porosity conductive substrates, in situ growth of MOF nanosheets, bimetallic synergy, and unique layering. This research provides a promising strategy for the application of MOF materials in the field of electrocatalysis. [ABSTRACT FROM AUTHOR]

The development of hydrogen evolution reaction (HER) electrocatalysts with outstanding efficiency and favorable stability at all pH values is of great significance but still a dominating challenge toward the development of electrochemical water-splitting technology. Herein, CoRu alloy nanoparticles assembled in Co4N porous nanosheets (named as CoRu@Co4N) have been successfully achieved from Ru(OH)3@Co(OH)2 through a one-step nitridation process. Benefiting from the unique structure, inherent alloy properties and strong alloy-support interaction derived from the in situ transformation, the resultant hybrids exhibit superior HER activities over a wide pH range, achieving very low overpotentials of 13 mV, 44 mV and 15 mV at 10 mA cm−2 under alkaline, neutral and acidic conditions, respectively. Such activities surpass most reported electrocatalysts and are comparable or even transcendent to commercial Ru/C and Pt/C. Furthermore, CoRu@Co4N also exhibits outstanding stability during the accelerated degradation test (ADT) and chronopotentiometry. Our work provides a new approach for designing pH-universal Ru-involved HER electrocatalysts with remarkable efficiency and prominent durability. [ABSTRACT FROM AUTHOR]

It is highly desirable for porous coordination polymers (PCPs), including metal–organic frameworks (MOFs) and Prussian blue analogues (PBAs), to retain their intrinsic characteristics in electrocatalysis, instead of being used as precursors or templates for further total conversion to other compounds via high-temperature calcination. Here, a S-treated two-dimensional (2D) CoFe bimetallic PBA grown on carbon fiber paper (CFP) (named S-CoFe-PBA/CFP) is assembled and applied as a highly efficient oxygen evolution reaction (OER) electrocatalyst in 1 M KOH. The resultant S-CoFe-PBA/CFP demonstrates significantly improved OER catalytic activity; overpotentials of only 235, 259, and 272 mV are needed to drive current densities of 10, 50, and 100 mA cm−2, respectively, with a super low Tafel slope of 35.2 mV dec−1. Even more noteworthy, a current density of 90 mA cm−2 can be achieved when a potential of 1.5 V vs. RHE is applied, which is 6.4 times higher than that of commercial Ir/C in the same environment. The outstanding electrocatalytic performance can be ascribed to two reasons caused by the S-treatment process. On one hand, H+ from intermediates of *OH and *OOH can be captured by –SOx distributed on the surface of the catalyst, thus accelerating the breaking of O–H; on the other hand, partial phase transformation of CoFe-PBA leads to the in situ formation of amorphous CoSx nanogauze on the surface, and the resultant electronic interactions between the two phases contribute much to the improvement of charge transfer and adsorption for OER intermediates. This work provides a new avenue for the design of highly efficient PCP-based OER electrocatalysts. [ABSTRACT FROM AUTHOR]

The obtained Ru-NiFeP/NF electrode exhibited distinguished electrocatalytic performance and extraordinary durability HER and OER in acidic, neutral and alkaline conditions. • Ru doped bimetallic phosphide (Ru-NiFeP/NF) was synthesized. • Ru-NiFeP/NF characterized excellent HER activity in all pH media. • Ru-NiFeP/NF presented superior OER and overall water splitting activity. • Ru doping can induce strong electron interactions and endow a better intrinsic activity. The exploration of earth-abundant, highly active, and stable electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is a vital but challenging step for sustainable energy conversion processes. Herein, a super-low ruthenium (Ru) (0.6 wt%) doped bimetallic phosphide derived from 2D MIL-53(NiFe) MOF nanosheets (i.e., Ru-NiFeP/NF) on nickel foam was developed via a continuous two-step hydrothermal followed by phosphorization process. The as-obtained Ru-doped NiFeP/NF with optimized electronic structure and enhanced electric conductivity delivers admirable performance for HER in a wide pH range, which requires overpotentials of 29, 105, and 56 mV to reach current density of 10 mA·cm−2 in acid, neutral, and alkaline media, respectively. For the OER, only requires an overpotential of 179 mV to achieve 10 mA·cm−2 in alkaline media. In a two-electrode alkaline electrolyzer, the as-prepared Ru-NiFeP/NF electrodes only need 1.47 V to yield 10 mA·cm−2, which is superior to the integrated RuO 2 and Pt/C couple electrode (1.5 V). This work highlights the rational design of MOF-derivates and electronic structure engineering strategy by heteroatom doping, which can be extended to design and prepare other high-performance MOF-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Developing highly efficient, low-cost and superior stable electrocatalysts for the oxygen evolution reaction (OER) is essential for coping with global energy shortage and environmental crisis. In this article, ACo 2 O 4 /NF (A = Mn, Zn, Ni) composites were synthesized via a facilely hydrothermal and calcination method and used as electrocatalytic water oxidation catalysts. The hybrid structure, chemical composition, oxidation state and surface morphology of ACo 2 O 4 /NF (A = Mn, Zn, Ni) has been confirmed by powder X-ray diffraction (XRD), energy dispersive X-ray (EDX), X-ray photoelectron (XPS), scanning electron microscopy (SEM), transmission Electron Microscope (TEM) and Brunaure-Emmett-Teller (BET) analysis. Such self-supported NiCo 2 O 4 /NF hybrid shows a smaller overpotential of 271 mV at current density of 10 mA cm −2 in 1 M KOH, which is comparable to most reported NiCo 2 O 4 materials (monomer or composite) for OER. Influence on catalytic activity of doping different metal ions in ACo 2 O 4 /NF was investigated systematically for the first time. Improved electrocatalytic activity of NiCo 2 O 4 /NF is attributed to the special homogeneous urchin-like structure and porous property. [ABSTRACT FROM AUTHOR]

The obtained NiFe-LDH@Fe-MOF/IF-2 electrode with unique hierarchical structure exhibited distinguished electrocatalytic performance and extraordinary durability OER in alkaline conditions. [Display omitted] • The NiFe-LDH@Fe-MOF/IF-2 was synthesized through a simple two-step hydrothermal method. • NiFe-LDH@Fe-MOF/IF-2 characterized excellent OER activity in alkaline conditions. • NiFe-LDH@Fe-MOF/IF-2 in-situ growth on the surface of IF improves conductivity and stability. • In situ partial transformation of amorphous NiFe-LDH greatly improves the OER performance. Metal-organic frameworks (MOFs) have been extensively researched in recent years benefiting from the large surface area, abundant active centers, and adjustable structure. However, low conductivity and inaccessible active sites severely hinder its application in water electrolysis. Herein, a self-supporting electrocatalyst by developing MOF derivative on the surface of iron foam (IF) was synthesized through a self-templated partial transformation strategy. In addition, a series of catalysts with different morphologies were synthesized by adjusting the amount of Ni and the reaction time. Profiting from the unique hierarchical structure with large active area and abundant active sites, strong combination of highly active amorphous NiFe-LDH and Fe-MOF, and high conductivity and stability of the MOFs array in situ growth on IF, the resulting NiFe-LDH@Fe-MOF/IF-2 shows excellent oxygen evolution reaction (OER) activity in alkaline electrolyte with required overpotentials of 183, 237 and 257 mV to achieve current densities of 10, 100, and 200 mA cm−2, respectively, and long-term stability for at least 20 h. This work provides new insights for the design and development of self-supporting MOFs derived high performance electrocatalysts. [ABSTRACT FROM AUTHOR]