Unveiling high intrinsic activity of Co3Mo alloy and metallic Ni embedded in CoNiMo-O nanosheets arrays for hydrogen evolution reaction

Developing robust and efficient electrocatalysts to boost hydrogen evolution reaction (HER) in alkaline solution is a crucial issue for H-2 energy. One of the effective strategies is to fabricate excellent electrocatalysts by embedding carbon shell-encapsulated transition metals or alloys in metal oxides through metal-organic frameworks (MOFs) as precursor. Herein, three multiphase composite HER catalysts (NF/CoNiMo-500, 600, 700) are exploited by using NF/CoNi-MOF-74 as template. Specially, the NF/CoNiMo-500 shows optimal HER activity, which is constructed by nesting graphitized carbon wrapped Co3Mo alloy and metallic Ni nanoparticles into amorphous CoNiMo-oxide (CoNiMo-O) nanosheets. It requires the lowest overpotential of 34 mV to reach the current density of 10 mA/cm(2), demonstrating the smallest Tafel slope of 58 mV/dec. Importantly, the water-alkali electrolyzer applying NF/CoNiMo-500 as cathode and NF/IrO2 as anode exhibits a low voltage of 1.39 V at 10 mA/cm(2) and good stability. The density functional theory (DFT) calculations reveal the high intrinsic activity of Co3Mo alloy and metallic Ni contributes significantly to the optimal electrocatalytic performance of CoNiMo-500. This work opens up a new orientation to synthesize microscale MOF-74 arrays and develop efficient HER electrocatalysts by combining carbon shell-encapsulated metals and alloys with oxides.