Photoelectrochemical water splitting using TiO₂/α-Fe₂O₃ heterojunction films produced by chemical vapour deposition

This study reports the enhanced photoelectrochemical (PEC) performance of TiO₂/α-Fe₂O₃ heterostructure films fabricated via a sequential aerosol-assisted chemical vapour deposition (AACVD) of hematite at 450 °C, followed by atmospheric pressure CVD (APCVD) of anatase TiO₂ with controlled thickness. Structural analyses (XRD, Raman, XPS) confirmed phase purity and oxidation states, while UV-vis spectroscopy revealed a narrowed bandgap and extended visible light absorption for the heterostructures compared to pristine films. The optimized TiO₂/α-Fe₂O₃ (8 min) photoanode achieved a photocurrent density of 1.75 mA cm^-2 at 1.23 V vs. RHE in 1.0 M NaOH under AM 1.5G illumination, representing a ∼150% improvement over pure α-Fe₂O₃. Incident-photon-to-current efficiency (IPCE) reached 7.47% at 420 nm, with enhanced performance sustained across the visible range. Transient absorption spectroscopy (TAS) revealed prolonged charge carrier lifetimes, indicating suppressed electron-hole recombination. The heterojunction design also improved stability, maintaining performance for over 16 h compared to 6.5 h for hematite alone. These synergistic effects including narrowed bandgap, efficient charge separation, and enhanced light harvesting highlight the novelty of combining AACVD and APCVD in fabricating TiO₂/α-Fe₂O₃ heterostructures as durable, high-performance photoanodes for scalable solar hydrogen generation.