Regulating oxygen vacancies to optimize the electronic structure and catalytic activity of tungsten oxides for hydrogen evolution reaction.

The undesirable intrinsic activity of tungsten oxides derived from poor conductivity and adverse hydrogen absorption energy is insufficient for their practical application. Herein, the tungsten oxides with adjustable oxygen vacancies were synthesized by a facile pyrolysis of ammonium paratungstate hydrate in controllable atmospheres. The structural characterizations confirmed that oxygen vacancies and crystalline phases in tungsten oxides depend on the pyrolysis atmosphere. The electrochemical test indicated a strong dependence between catalytic activity and oxygen vacancies in tungsten oxides. Combining experimental results and density functional theory calculations verified that introducing oxygen vacancies into tungsten oxides effectively modulates the surface electronic structure. The enhanced electronic conductivity by reducing band gap accelerates the electron transfer from catalysts into the reactive species. The optimized hydrogen adsorption energy by electron migration from O into W promotes the activation of reactive species at W sites and the desorption from O sites, thereby accelerating the reaction kinetics. The regulated oxygen vacancies in tungsten oxides was availably achieved by controlling the annealing atmospheres for ammonium paratungstate hydrate. The as-prepared tungsten oxide catalysts exhibit a strong dependence between oxygen vacancies contents and catalytic activity for hydrogen evolution reaction. The experimental observations and theoretical calculations confirm that oxygen vacancies introduced into tungsten oxides can enhance the electronic conductivity and optimize the hydrogen adsorption energy to remarkably improve the catalytic activity. [Display omitted] • Oxygen vacancies in WO 3 were regulated by controlling annealing atmospheres. • WO 3 exhibits a strong dependence between oxygen vacancies and catalytic activity. • Introducing oxygen vacancies reduces band gap to improve electronic conductivity. • Oxygen vacancies optimize hydrogen adsorption energy on tungsten oxides. [ABSTRACT FROM AUTHOR]