Interfacial engineering of a multijunctional In₂O₃/WO₃@Ti₄N₃T_x S-scheme photocatalyst with enhanced photoelectrochemical properties

Achieving high photoelectrochemical conversion efficiency requires the logical layout of a composite photocatalyst with optimal charge separation and transfer with ideal light harvesting capabilities to enhance the photocatalytic performance and the degradation rate towards organic pollutants. Herein, a novel In₂O₃/WO₃@Ti₄N₃T_x S-scheme heterojunction was successfully synthesized and confirmed through valence band VB-XPS and Mott Schottky combined analysis. The formed MXene-doped In₂O₃/WO₃@Ti₄N₃T_x S-scheme significantly enhances the charge flow and spatial separation with an improved oxidation and reduction ability. An in-built interfacial electric field at the WO₃-In₂O₃ boundary enhanced the light-harvesting capacity, whereas Ti₄N₃T_x MXene offers a unique electron trapping effect which effectively lowers high charge carrier recombination rate-related photocatalytic deficit. It preserves the exceptional redox potency of the photocatalyst by providing a directed acceleration and effective separation of the photogenerated charges. A high carrier density (N_D = 7.83 × 10²¹ cm⁻³) with a lower negative flat band (V_FB = −0.064 V vs. Ag/AgCl) was obtained by Mott-Schottky analysis for 3 wt% In₂O₃/WO₃@Ti₄N₃T_x, an indicator that a low overpotential is needed to activate photocatalytic reactions. This study, therefore, provides a novel thought for the design and fabrication of an S-scheme heterojunction for photocatalytic reactions for mineralization of organic pollutants in water and clean energy production.