Co, N, and P co-doped few-layer graphene derived from cobalt phthalocyanine-based covalent organic polymers as bifunctional electrocatalysts for overall water splitting

Abstract

Water electrolysis is considered to be one of the most promising approaches for developing sustainable energy technologies, however, the high cost and lack of stability of traditional precious metal electrocatalysts have hindered the development of the field of water electrolysis. Covalent organic polymers have greater potential for the preparation of low-cost electrocatalysts with high efficiency and long-term stability due to their low cost, controllable chemical composition, and rich pore structure. Cobalt phthalocyanine-based covalent organic polymers were loaded onto few-layer graphene by a hydrothermal method and then pyrolyzed to produce Co, N, and P co-doped few-layer graphene (Co–N/P-FG-700). Co–N/P-FG-700 demonstrates superior performance for oxygen evolution reaction (OER) due to the synergistic effect of abundant active sites and conductive carriers, with an overpotential of 358 mV at a current density of 10 mA cm−2 and 90% of the current density after 50,000 s of stability testing. Co–N/P-FG-700 exhibits excellent results for hydrogen evolution reaction (HER) with an overpotential of −275 mV at a current density of −10 mA cm−2 and a current density retention of 93% after a 50,000 s stability test. This study provides a rational pathway for the design of low-cost, high-performance, stable bifunctional OER/HER electrocatalysts.