Construction of a built-in electric field in Mo-doped Ni/WO3 to enhance asymmetric charge distribution for efficient overall water splitting

Abstract

Constructing an asymmetric charge distribution and built-in electric field (BIEF) has proven to be an effective strategy for enhancing the catalytic performance of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts. Herein, a Mo-doped Ni/WO₃ heterojunction catalyst was immobilized on Ni foam for enhancing the performance of the HER and OER. The constructed Ni/WO₃ heterointerface facilitates electron transport, while the incorporation of Mo further amplifies charge asymmetry in the interfacial region. The optimized Mo₃–Ni/WO₃ catalyst exhibits excellent performance, requiring only 13 mV and 328 mV overpotential to reach current densities of 10 and 100 mA cm⁻² for the HER and OER, respectively. Besides, it maintains stable overall water splitting performance at 100 mA cm⁻² for 90 h. The asymmetric distribution of Ni/WO₃ interfacial charge is promoted and electron transport is enhanced by Mo doping. Theoretical results show that element doping in the heterostructure turns W sites into additional adsorption centers, optimizing the energetics of H* adsorption during the HER. Mo doping reduces the work function (φ) of Mo₃–Ni/WO₃, promoting efficient electron transfer and lowering the energy barrier for intermediate formation, thereby enhancing OER activity. This strategic modulation of charge asymmetry in heterojunction architectures provides a new approach for the rational design of high-performance bifunctional electrocatalysts.