High-performance photocatalytic reduction of Cr(VI) using a retrievable Fe-doped WO₃/SiO₂ heterostructure

The enhancement of the photocatalytic performance of pristine WO₃ was systematically adjusted due to its fast recombination rate and low reduction potential. A designed heterostructure photocatalyst was necessarily synthesised by Fe³⁺ metal ions doping into WO₃ structure with and composition modification. In this study, we synthesised a retrievable Fe-doped WO₃/SiO₂ heterostructure using a surfactant-assisted hydrothermal method. This heterostructure was then employed as an effective photocatalyst for the removal of Cr(VI) under visible light irradiation. Enlarged photocatalytic reduction was observed over a synergetic 7.5 mol% Fe-doped WO₃/SiO₂-20 nanocomposite, resulting in dramatically increased activity compared with undoped WO₃ and SiO₂ nanomaterials under visible light illumination within 90 min. The presence of 7.5 mol% Fe³⁺ ion dopant in WO₃ optimised electron-hole recombination, consequently reducing WO₃ photocorrosion. After adding SiO₂ nanoparticles, the binary WO₃-SiO₂ nanocomposite played roles as both adsorbent and photocatalyst to increase specific surface area. Thus, the 7.5 mol% Fe-doped WO₃/SiO₂-20 nanocomposite catalyst had more active sites on the surface of catalyst, and enhanced photocatalytic reduction was significantly achieved. The results showed 91.1% photocatalytic reduction over the optimum photocatalyst, with a photoreduction kinetic rate of 21.1 × 10^-3 min^-1, which was approximately four times faster than pristine WO₃. Therefore, the superior optimal photocatalyst demonstrated reusability, with activities decreasing by only 9.8% after five cycles. The high photocatalytic performance and excellent stability of our photocatalyst indicate great potential for water pollution treatments.