Boosting hydrogen evolution of nickel phosphide by expanding built-in electric field with tungsten oxide.

Manipulating the built-in electric field (BIEF) in the catalyst to regulate the electronic structure and improve the carrier transport is a promising approach, but it is rarely applied in the design of hydrogen evolution reaction (HER) catalysts. In this study, the electrochemical microenvironment of nickel phosphide supported on nickel foam (Ni 2 P/NF) has been modified by introducing tungsten oxide (WO 3) through simple ion group exchange strategy, thereby expanding the BIEF and enhancing the electron transport property. As a direct outcome, the target catalyst (20-WO 3 /Ni 2 P/NF) exhibits ultralow overpotential of 301 mV at high current density of − 1000 mA cm−2. Additional characterization and density functional theory calculations demonstrate that the WO 3 can not only serve as a new hydrogen adsorption active site, but also effectively decrease the dissociation energy of water molecules at the nickel site, which results in rapid production and consumption of protons and enhancing the overall catalytic activity. [Display omitted] • A WO 3 -regulated Ni 2 P/NF has been developed by the method of ion-group exchange and low temperature phosphating strategy. • The modification of WO 3 expands the BIEF of Ni 2 P/NF and promote the rapid dissociation of water molecules on it. • The newly introduced WO 3 can be used as the active site of hydrogen adsorption. • The 20-WO 3 /Ni 2 P/NF exhibits the superior HER activity and only requires low overpotential of 301 mV to reach 1000 mA cm−2. [ABSTRACT FROM AUTHOR]