Oxygen-deficient WO3−x nanoplate array film photoanode for efficient photoelectrocatalytic water decontamination

Photoelectrocatalysis (PEC) represents a promising method for water decontamination, but the overall performance is limited by slow interfacial charge transfer. In this study, we address this limitation by creating an efficient PEC system with oxygen-deficient WO 3−x nanoplate array film serving as photoanode through surface reduction method. Oxygen vacancy had a slight impact to catalytic activity of photoanode, but exhibited an enhanced performance when anodic polarization was imposed. Based on a front-side illumination and potential of 1.2 V vs standard hydrogen electrode (SHE), the WO 3−x photoanode produced a photocurrent being 7.3 times as WO 3 photoanode, indicating a substantially enhanced interfacial charge transfer. Both WO 3 and WO 3−x electrodes showed an insignificant removal of 4-chlorophenol (4-CP) and dechlorination under individual photocatalytic condition. When anodic polarization was applied at 1.2 V vs SHE, 85.5% removal of 4-chlorophenol (4-CP) and 48% dechlorination efficiency could be obtained for WO 3−x photoanode, accounting for the values being 32.7% and 25.8% higher than that for WO 3 photoanode. The corresponding first-order kinetic constant for 4-CP removal by WO 3−x ( k  = 0.0157 min −1 ) was approximately 2.53 times as that by WO 3 ( k  = 0.0062 min −1 ). The improved PEC performance of WO 3−x photoanode under low potential bias should result from faster interfacial charge transfer, mitigation of electron-hole recombination, and production of higher amount of hydroxyl radical ( OH). This study not only suggests the important role of oxygen vacancy in PEC system, but also provides a new strategy to develop a full solar-energy-based water purification system.