Design of molybdenum phosphide @ nitrogen-doped nickel-cobalt phosphide heterostructures for boosting electrocatalytic overall water splitting

Transition metal phosphides (TMPs) are one of the most promising alternatives to noble metal electrocatalysts, but so far their activity and stability still fall short of expectations. Here, we prepare nitrogen-doped nickel-cobalt phosphide (N-NiCoP) and molybdenum phosphide (MoP) heterostructures engineered on nickel foam (NF) with nanosheet structure by high-temperature annealing and low-temperature phosphorylation. Notably, heteroatomic N doping and heterostructures construction are achieved together through a simple co-pyrolysis method. The distinctive composition can synergistically promote the electron transfer, lower the reaction barriers, thus improving the catalytic performance. Therefore, the modified MoP@N-NiCoP requires low overpotentials of 43 mV and 232 mV to reach 10 mA cm-2 current density for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) accompanied by satisfactory stability in 1 M KOH. Density functional theory (DFT) calculations reveal the electron coupling and synergistic interfacial effects at the heterogeneous interface. This study provides a new strategy for heterogeneous electrocatalysts with elemental doping to promote hydrogen applications.