Interfacial engineering of Co nanoparticles/Co2C nanowires boosts overall water splitting kinetics

Utilizing cobalt carbide (such as Co2C) as water electrolysis catalyst remains a significant challenge due to the high overpotentials during the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, in terms of theoretical predictions, we confirm that metallic Co exhibits HER catalytic selectivity, whereas Co2C has moderate binding energies for OER intermediates, thus boosting water splitting kinetics by the compatible integration. Experimentally, we present an interface engineering of Co nanoparticles and Co2C nanowires on carbon cloth (CC) resulting in a unique Co-Co2C/CC electrocatalyst. The resultant Co-Co2C/CC entails low overpotentials of only 261 mV for OER and 96 mV for HER at the current density of 10 mA cm−2, which are one of the highest activities yet reported for cobalt carbide-based materials. Moreover, the assembled electrolyzer can be driven by a solar cell. This work enlightens a novel avenue for the rational design of metal carbide-based highly efficient electrocatalysts.