Porous carbon framework decorated with carbon nanotubes encapsulating cobalt phosphide for efficient overall water splitting

Exploration of catalysts for water splitting is critical for advancing the development of energy conversion field, but designing bifunctional catalysts remains a major challenge. Herein, we demonstrate the N-doped carbon nanotube (NCNT)-grafted N-doped carbon (NC) framework embedding CoP nanoparticles (CoP@NC/NCNT) as hydrogen and oxygen evolution reaction (HER and OER) catalysts for water splitting. As a result, the CoP@NC/NCNT electrode requires the overpotentials of 106 and 177 mV at 10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH solutions for HER, respectively. Moreover, an overpotential of 324 mV for OER can drive 10 mA cm-2 in 1.0 KOH. The CoP@NC/NCNT-based electrolyzer derives a current density of 10 mA cm-2 at a low voltage of 1.72 V in 1.0 M KOH and remains stable for 10 h. The outstanding electrocatalytic performance is mainly attributed to the hierarchical structure with rich branches and highly active component of CoP. The intimate contacts between hierarchical porous NC frameworks by cross-linked NCNTs create a 3D conductive network, which facilitates electron or mass transfer and activates CoP. This work offers a novel route for preparing hierarchical carbon framework encapsulated metal phosphide particles for potential applications in energy conversion field.