Facet-directed multiphase TiO2–BiVO4 heterojunction for directional charge transport and photoelectrochemical cathodic protection

Regulating charge transport across semiconductor heterojunctions is critical for photoelectrochemical (PEC) energy conversion and photoelectrochemical cathodic protection (PECP). Herein, we report a facet-directed multiphase and defect-regulated strategy to tailor interfacial energetics and carrier dynamics in TiO 2 –BiVO 4 heterostructured photoanodes. By introducing Bi-containing domains onto TiO 2 nanosheets with co-exposed {001}/{101} facets, the optimized TiO 2 –BiVO 4 -T forms a spatially heterogeneous multiphase architecture consisting of residual α-Bi 2 O 3 , tetragonal BiVO 4 , and monoclinic BiVO 4 . TiO 2 facet configuration, multiphase BiVO 4 domains, and defect-associated electronic modulation are proposed to regulate local band alignment, facilitate charge separation, and favor electron extraction. Spectroscopic characterization, electrochemical analysis, density functional theory calculations, and light-assisted Kelvin probe force microscopy (KPFM) show modified interfacial energetics, photoinduced surface-potential response, and improved carrier-transfer behavior. Accordingly, TiO 2 –BiVO 4 -T exhibits higher charge-separation efficiency, stronger PEC activity, and stable solar-driven cathodic protection for stainless steel and copper. The relationship between structure, electronic modulation, and PECP response identifies facet-selective formation of multiphase domains as a practical route for photoelectrodes used in corrosion protection and solar-energy conversion.