Enhanced Cr(VI) photoreduction in water using TiO2/CuWO4 photocatalytic coating

This study presents the rational design of a TiO2/CuWO4 heterostructure coating fabricated on a titanium substrate, where a TiO2 layer was first formed via plasma electrolytic oxidation (PEO), followed by the hydrothermal growth of CuWO4 nanoparticles, resulting in outstanding Cr(VI) photoreduction performance. This study reports the rational design of a hydrothermally post-treated PEO-derived TiO2/CuWO4 heterostructure coating with exceptional Cr6+ photoreduction activity. Comprehensive characterization (FE-SEM/EDS, XRD, AFM, UV–Vis DRS, PL, and Mott–Schottky analysis) revealed that hydrothermal CuWO4 integration induces: (i) a microporous TiO2 base layer supporting a hierarchical structure with uniformly distributed CuWO4 particles; (ii) the formation of a Type-II heterojunction that facilitates efficient e−/h+ separation; and (iii) a super hydrophilic surface with enhanced roughness, improving reactant accessibility. Furthermore, the influence of scavengers was systematically investigated, confirming the critical roles agents (e−, O21, HO⦁, and O2⦁−). Among scavengers, oxalic acid and potassium persulfate exhibited pronounced contributions by enhancing hole- and electron-driven pathways. A mechanism, combining heterojunction-driven charge transfer is proposed, providing a scalable and durable photocatalytic coating solution for heavy-metal remediation.