Photoelectrochemical water splitting using TiO/α-FeO heterojunction films produced by chemical vapour deposition.

This study reports the enhanced photoelectrochemical (PEC) performance of TiO/α-FeO heterostructure films fabricated a sequential aerosol-assisted chemical vapour deposition (AACVD) of hematite at 450 °C, followed by atmospheric pressure CVD (APCVD) of anatase TiO 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 TiO/α-FeO (8 min) photoanode achieved a photocurrent density of 1.75 mA cm at 1.23 V RHE in 1.0 M NaOH under AM 1.5G illumination, representing a ∼150% improvement over pure α-FeO. 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 TiO/α-FeO heterostructures as durable, high-performance photoanodes for scalable solar hydrogen generation.