Enhancing the Photocatalytic Performance of BiVO4 for Micropollutant Degradation by Fe and Ag Photomodification

Abstract

Wider application of BiVO4 (BVO) for photocatalytic water treatment is primarily limited by its modest photocatalytic effectiveness, despite its appropriately narrow band gap for low-cost, sunlight-facilitated water treatment processes. In this study, we have photomodified an isotype BVO, consisting of a tetragonal zircon and monoclinic scheelite phase, with Fe (Fe@BVO) and Ag (Ag@BVO) ionic precursors under UV illumination in an aqueous ethanol solution in order to assess their effect on the opto-electronic properties and effectiveness for the removal of ciprofloxacin (CIP). Fe@BVO failed to demonstrate enhanced effectiveness over pristine BVO, whereas all Ag@BVO achieved improved CIP degradation, especially 1% Ag@BVO. At pH 4 and 6, 1% Ag@BVO demonstrated nearly 24% greater removal of CIP than BVO alone. Photomodification with Fe created surface oxygen vacancies, as confirmed by XPS and Mott–Schottky analysis, which facilitated improved electron mobility, although no distinct Fe-containing phase nor Fe-doping was detected. On the other hand, the introduction of mid-band gap states by oxygen vacancies decreased the reducing power of the photogenerated electrons as the flat band potentials were shifted to more positive values, thus likely negatively impacting superoxide formation. In contrast, Ag-photomodification (Ag@BVO) resulted in the formation of Ag2O/AgO and Ag nanoparticles on the surface of BVO, which, under illumination, generated hot electrons by surface plasmon resonance and enhanced the mobility of photogenerated electrons. Our research underscores the pivotal role of photogenerated electrons for CIP degradation by BiVO4-based materials and emphasizes the importance of appropriate band-edge engineering for optimizing contaminant degradation.