Facile Strategy for Synthesizing Non-Stoichiometric Monoclinic Structured Tungsten Trioxide (WO_{3- x}) with Plasma Resonance Absorption and Enhanced Photocatalytic Activity

Oxygen vacancy defects play an important role in improving the light-capturing and photocatalytic activity of tungsten trioxide (WO₃). However, the hydrogen treatment method that is commonly used to introduce oxygen vacancies is expensive and dangerous. Therefore, the introduction and control of oxygen vacancy defects in WO₃ remains a challenge. Here, we demonstrated that oxygen vacancies could be successfully introduced into WO_3-x while using a facile method through low temperature annealing in alcohol. The obtained WO_3-x samples with optimal oxygen vacancies showed strong absorption of light, extending from the ultraviolet to the visible and near-infrared regions, and exhibits strong plasmon resonance from 400⁻1200 nm peaking at approximately 800 nm. When compared to pristine WO₃, the photocatalytic activity of WO_3-x was greatly improved in the ultraviolet and visible regions. This study provides a simple and efficient method to generate oxygen vacancies in WO₃ for photocatalysis, which may be applied in the photoelectrochemical, electrochromic, and photochromic fields. Because oxygen vacancy is a common characteristic of metal oxides, the findings that are presented herein may be extended to other metal oxides.