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

Abstract

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.