One-pot synthesis of Fe2O3-supported tungsten trioxide heterojunctions for rapid and highly recyclable photocatalytic nitrobenzene reduction

Aromatic compounds have recently gained attention as a significant environmental issue because of their persistent nature and potential mutagenic effects. To address this issue, scientists have turned to photocatalytic degradation techniques as a promising solution, particularly for converting toxic nitroaromatic compounds into safer amine derivatives. In this work, WO₃ nanostructures were synthesized using a polymer surfactant-assisted growth method, followed by incorporating 5.0–20.0 wt% Iron(III) oxide (Fe₂O₃) nanoparticles to develop visible-light-active photocatalysts. Structural and optical analysis revealed that incorporating Fe₂O₃ into WO₃ resulted in a mesoporous structure while enhancing its optical performance. Notably, adding 15 wt% Fe₂O₃ drastically reduced the bandgap (Eg) of WO₃ nanocrystals from 3.0 eV to 2.54 eV, demonstrating greatly improved visible-light capture. This optimized photocatalyst was employed for the efficient photoreduction of nitrobenzene (NB) to aniline (AN) under visible light. Using a 2.0 g/L dose of 15 wt% Fe₂O₃-WO₃, complete NB conversion to AN was achieved in just 40 min, with a high reaction rate of 7.5 x 10^-2 min⁻¹, attributed to enhanced charge carrier mobility and effective electron-hole separation. Additionally, the catalyst demonstrated excellent recyclability, maintaining 92.5 % of its initial efficiency after 5 regeneration cycles. Mechanistic studies revealed that the Fe₂O₃-WO₃ heterojunction facilitates an S-scheme charge transfer pathway, optimizing redox potential while minimizing recombination losses. These findings highlight the potential of such sustainable photocatalysts for industrial-scale chemical synthesis.