Optimizing Heterointerface of Co2P–CoxOy Nanoparticles within a Porous Carbon Network for Deciphering Superior Water Splitting

Abstract

It is of great significance to design a bifunctional electrocatalyst for promoting hydrogen (HER) and oxygen (OER) evolution reactions simultaneously. Herein, inspired by the appropriate H atom binding energy on cobalt phosphides and excellent oxygen evolution kinetics on cobalt oxides, the regulative synthesis of a Co2P–CoxOy (CoxOy = CoO or Co3O4) heterogeneous nanoparticle-anchored porous carbon network electrocatalyst via one-pot heat treatment is reported. The as-synthesized Co2P–Co3O4/C exhibits superior electrochemical activity with low overpotentials of 86 mV for HER and 246 mV for OER at 10 mA cm−2 in an alkaline electrolyte. Moreover, compared to the commercial Pt/C || RuO2/C system, the Co2P–Co3O4/C || Co2P–Co3O4/C system presents outstanding activity toward overall water splitting (1.55 V@10 mA cm−2), which is well maintained over long-term (120 h) electrocatalysis. Density functional theory calculations show that the rich interfaces between Co2P and Co3O4 offer a synergistic effect, which enables Co2P–Co3O4/C as an excellent electrocatalyst toward both HER and OER.