Fluorination of the WO₃ Photoanode to Promote Interfacial Charge Transfer for Efficient Photoelectrocatalytic Performances

Abstract

To improve the interfacial charge transfer over a tungsten oxide (WO 3 ) photoanode for an efficient photoelectrocatalytic (PEC) process, WO 3 was fluorinated in a solvothermal process in the presence of NH 4 F. It was shown that, after the fluorination with the molar ratio of NH 4 F to WO 3 at 0.4, the charge separation and charge injection efficiencies increased from 22.02 to 61.15% at 0.5 V vs Ag/AgCl and from 44.71 to 72.69% at 0.5 V vs Ag/AgCl, respectively, significantly enhancing the PEC performances for synergetic tetracycline degradation and H 2 evolution. Various characterization and density functional theory calculation results revealed that the incorporation of fluorine into the WO 3 lattice by fluorination substantially raises the Fermi level of WO 3 , which bends the energy bands of WO 3 more upward at the semiconductor/electrolyte interface. The intensified upward bending bands effectively promote charge transfer at the fluorinated WO 3 photoanode/electrolyte interface, achieving the observed efficient PEC performances.