Interfacial Sites between Cobalt Nitride and Cobalt Act as Bifunctional Catalysts for Hydrogen Electrochemistry

Abstract

Hydrogen (H2) electrochemistry primarily consists of two reactions: hydrogen evolution reaction in water for H2 production (HER) and hydrogen oxidation reaction in hydrogen fuel cells for H2 utilization (HOR). The realization of future hydrogen economy necessitates the development of low-cost and competent electrocatalysts for both HER and HOR. Herein, we report that partial nitridation of cobalt nanoparticles on current collectors results in rich Co2N/Co interfacial sites, which exhibit bifunctional activity for hydrogen electrochemistry, rivaling the state-of-the-art Pt counterparts tested under similar conditions. Our combined experimental and theoretical computation results demonstrate that Co2N/Co interfacial sites not only possess optimal hydrogen adsorption energy but also facilitate water adsorption and dissociation on the catalyst surface, all of which are beneficial to the electrocatalytic performance for both HER and HOR. In addition, our Co2N/Co electrocatalysts also demonstrate great tolerance against CO poisoning during long-term H2 oxidation.