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

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 Co 2 P–Co x O y (Co x O y = CoO or Co 3 O 4 ) heterogeneous nanoparticle‐anchored porous carbon network electrocatalyst via one‐pot heat treatment is reported. The as‐synthesized Co 2 P–Co 3 O 4 /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 || RuO 2 /C system, the Co 2 P–Co 3 O 4 /C || Co 2 P–Co 3 O 4 /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 Co 2 P and Co 3 O 4 offer a synergistic effect, which enables Co 2 P–Co 3 O 4 /C as an excellent electrocatalyst toward both HER and OER.