Manipulating the Electronic State of Tungsten Carbide Using CoNi@N-doped Carbon Derived from Bimetallic MOF for Enhanced Electroreduction Reactions

Abstract

Development of highly efficient, low-cost and stable electrode materials for hydrogen evolution reaction (HER) from water reduction has faced great challenges. Here a porous transitional metal carbide (TMC) with electron-deficient surface was successfully fabricated using metal-organic framework (MOF) as template. During pyrolysis, the initially generated CoNi alloy particles could gather the surrounding tungsten (VI) and molybdenum (VI) species, and induce their carbonization to form carbides (Mo2C and WC, named as MxC) shell. Finally, the core-shell CoNi@MxC@NC hybrid material was fabricated. As noted, the Co1Ni1@MxC@NC with optimal Co/Ni ratio presented a very low overpotential of 103 mV at 10 mA cm-2 and a low Tafel slope of 112.2 mV·dec-1 in an alkaline media, which was very close to that of commercial Pt/C. This catalyst also completed the reduction of p-nitrophenol (10 mM) to p-aminophenol within 3 h. The performance exceeded most reported non-noble metals and even some precious electrocatalysts. The synergy between MxC and CoNi for HER was studied experimentally and theoretically. Except for the intrinsic activity of carbides, the adjent CoNi species largely induce the charge redistribution at their interface. The positively charged WC was helpful for the adsorption and dissociation of molecular H2O and release of hydrogen.