Tailoring the geometric and electronic structure of tungsten oxide with manganese or vanadium doping toward highly efficient electrochemical and photoelectrochemical water splitting

Abstract

Tailoring the geometric and electronic structure is dynamically important for designing highly active catalyst materials, which remains a great challenge. Herein, our combined experimental and density functional theory (DFT) calculations demonstrate that the electrocatalytic and photoelectrochemical activity of WO₃ changes non-monotonically with the Mn or V doping concentration due to local changes in the reduced nature of WO₃ and the formation of oxygen vacancies. For the hydrogen evolution reaction, at optimal Mn and V doping concentrations, the overpotential to reach ∼10 mA cm⁻² is reduced by −97 mV and −38 mV vs. RHE; the Tafel slope is also reduced from 121 to 68 and 41 mV per decade (mV dec⁻¹) compared to the undoped WO₃, respectively. The improved activity arises from the fine tuning of the electronic structure and lessened free energy for atomic hydrogen adsorption. For photoelectrochemical water splitting, the photocurrent density is increased from 0.61 mA cm⁻² for the undoped WO₃ to ∼1.38 mA cm⁻² and 2.49 mA cm⁻² for optimal Mn and V doping, respectively. The photocurrent density at an optimal V doping is approximately 1.8 and 4.1 times higher than that at the optimal Mn doping and undoped WO₃, respectively. Our work indicates a promising interface-engineering strategy for designing highly active non-precious electrocatalysts and photocatalysts for green energy conversion applications.