Electron structure customization of molybdenum phosphide via lanthanum doping toward highly efficient overall water splitting

Abstract

Due to its high electrical conductivity and platinum-like electronic structure, molybdenum phosphide (MoP) has attracted extensive attention as a potential catalyst for the hydrogen evolution reaction (HER) by water splitting. Nevertheless, in the oxygen evolution reaction (OER), the electrocatalytic performance of MoP did not achieve satisfactory results. Therefore, novel nitrogen-doped carbon-encapsulated La-doped MoP nanoparticles (La-MoP@N/C) are synthesized, which show outstanding durability and electrocatalytic activity in both HER and OER. Detailed structural characterization and calculations confirm that La doping not only effectively adjusts the electron density around Mo and P atoms, accelerates the adsorption and desorption processes, but also increases the number of active sites. Low overpotentials of 113 and 388 mV for HER and OER at 10 mA cm^-2 are achieved with the optimized La_0.025-Mo_0.975P@N/C. Furthermore, the two-electrode electrolyzer assembled with La_0.025-Mo_0.975P@N/C also presents impressive water splitting performance. This study indicates that rare earth doping can be used as an efficient strategy to control the local electronic structure of phosphides precisely, which can also be extended to other electrocatalysts.