Oxygen-deficient WO3 for stable visible-light photocatalytic degradation of acetaldehyde within a wide humidity range

Indoor VOCs pollution has attracted broad attention for its harm to mankind's health recent years. Photocatalytic degradation of indoor VOCs holds great prospects in addressing these health concerns in daily life. However, traditional photocatalysts have a large recombination rate of charge carriers and a decrease of the photocatalytic degradation efficiency under high relative humidity. Herein, uniform tungsten oxide nanoparticles with enriched oxygen vacancies (WO3-U) were synthesized by a direct annealing method with urea addition, which exhibited superior performance in the visible-light photocatalysis. The reaction rate constant value of photocatalytic acetaldehyde degradation over WO3-U catalyst was above 3 times higher than that of pristine WO3 sample. More importantly, the WO3-U catalyst maintained stable and excellent photocatalytic performance at relative humidity range of 25-100 %. Except for the enhanced photogenerated charges separation, abundant oxygen vacancies could effectively accelerate O-2 activation to generate center dot O-2(-), which accounted mainly for the initial conversion of acetaldehyde. Then the subsequent transformation of center dot O-2(-) into center dot OH to promoted the final mineralization of acetaldehyde. In addition, the presence of oxygen vacancies also facilitated H2O dissociation to form surface hydroxyl groups, which increased the adsorption of acetaldehyde, resulting in the consistent photocatalytic performance of WO3-U catalyst within a wide humidity range. This work provides guidelines to design visiblelight responsive photocatalysts with efficient activity at high humidity conditions for indoor VOCs degradation.