In-situ phosphating Co@Nitrogen-doping graphene boosts overall water splitting under alkaline condition

It is still challenging to design and synthesize highly efficient and noble-metal-free electrocatalysts for hydrogen/oxygen evolution reaction (HER/OER). Herein, we developed an in-situ phosphating Co@nitrogen-doping graphene to obtain N and P co-doped carbon-coated cobalt phosphide (CoP@N,P C) that could be used for overall water splitting. The unique 3D porous structure of CoP@N,P C is characterized by a large number of active catalytic sites. High wettability of catalyst in electrolyte solution facilitates the transfer of ions. The synergism between the CoP cores and N, P C shells improves the total hydrolysis performance of the electrocatalyst during the HER and OER. At the current densities of 10 mA/cm 2 (1 M of KOH), the HER overpotential recorded for the CoP@N,P C is 113 mV, and the OER overpotential is 320 mV. The cell voltage of the CoP@N,P C as bifunctional electrode for overall water splitting is 1.67 V (at 10 mA/cm 2 ), which is close to that of the full noble-metal electrode (RuO 2 || Pt/C, 1.58 V). The CoP@N, P C bifunctional catalyst can be potentially used to replace noble-metal electrodes to realize water splitting.