Modulating the Electronic Structure of Co in Co–Co₆Mo₆C₂ for Effective Oxygen Evolution Reaction

Tuning the electronic structure of the materials to an optimal state has been regarded as an attractive strategy for designing efficient oxygen evolution reaction (OER) electrocatalysts. In this study, ultrasmall Co–Co6Mo6C2 nanoparticles (2–6 nm) evenly dispersed on the nitrogen-doped carbon (CMC@NC) were constructed by pyrolysis of the precursor of hollow structured Co3O4 encapsulated in Mo7O246– polyaniline. The electronic structure of Co was controllably adjusted by regulating the ratio of Co/Mo in the Co–Co6Mo6C2 system. The optimized electrocatalyst exhibits an excellent OER performance with an overpotential of 266 mV at 10 mA cm–2 and an outstanding stability over a 70 h OER process. Based on the characterization results of before- or post-OER materials, it can be found that CMC@NC-120-750 has an optimized electronic structure for OER via drawing electrons from 3d metal Co by non-3d metal Mo6+, ultimately resulting in the highest oxidation peak and the highest amount of Co3+ (the real OER active sites). This study provides novel insight into the construction of efficient transition metal-based catalysts.