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 WO3-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 WO3-x photoanode produced a photocurrent being 7.3 times as WO3 photoanode, indicating a substantially enhanced interfacial charge transfer. Both WO3 and WO3-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 WO3-x photoanode, accounting for the values being 32.7% and 25.8% higher than that for WO3 photoanode. The corresponding first-order kinetic constant for 4-CP removal by WO3-x (k= 0.0157 min(-1)) was approximately 2.53 times as that by WO3 (k= 0.0062 min(-1)). The improved PEC performance of WO3-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 (center dot 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.