Improved photoelectrocatalytic performances over electrochemically reduced WO₃: implications of oxygen vacancies

The introduction of rich oxygen vacancies into the WO₃ lattice has been achieved through a facile and environmentally friendly route of electrochemical reduction. It has been shown that the electrochemical reduction treatment significantly increases the charge separation efficiency from 37.44% to 65.44% at 0.74 V vs. NHE, and charge injection efficiency from 15.06% to 58.20% at 0.74 V vs. NHE, leading to enhanced PEC performances for synergetic 4-CP degradation and H₂ evolution. Various characterization results well demonstrated that the formation of W⁵⁺ species resulting from the introduction of oxygen vacancies in the WO₃ lattice raises the Fermi level closer to the energy level of oxygen vacancies. The raised Fermi level achieves the substantial electron trap effect of the oxygen vacancies and further bends upward the band at the semiconductor/electrolyte interface, both of which play dominant roles in the effective interfacial transfer and separation of the photogenerated charges for enhanced PEC performances.