Synergistic role of salt-precursor-derived Cu-doping in solution-processed α-Fe₂O₃ films for enhanced charge separation and photocatalytic efficiency

Abstract Photoelectrochemical (PEC) water splitting exhibited a sustainable route for hydrogen (H₂) production, whereas Iron oxides (α-Fe₂O₃) found one of the most emerging materials as a photoanode owing to its intrinsic narrow bandgap of ~ 2.0 eV and high chemical stability. However, constraints such as poor conductivity and charges transport relative to required hinder its performance. However, substantial doping in α-Fe₂O₃ is the potential strategy to meet these challenges. This study demonstrates the simple growth of α-Fe₂O₃, and Cu-doped thin films from salt-precursors through a sequential steps of chemical mixing, precise spin coating, and subsequent post-heating treatment. This multi-step process ensures uniform film deposition and facilitates the incorporation of Cu into the α-Fe₂O₃ lattice with enhanced structural and functional properties. The systematic Cu incorporation into the α-Fe₂O₃ lattice was confirmed via both FT-IR and EDX analyses, while the enhanced conductivity, and improved charge transport behavior by electrical measurements. Experimental outcomes exhibited tunable wide band gaps, E g of 1.87–1.50 eV, improved visible light absorption with increased density of active sites on the film surface revealed by Cu doping. The PEC performance highlights significant photocurrent boosting with low onset potential, attributed to the catalytic role of Cu in accelerating oxygen evolution reaction (OER) kinetics. These findings reveal solution-processed salt-precursors-derived Cu-doped α-Fe₂O₃ has strong potential as a cost-effective and scalable solution for PEC hydrogen production highlighting the importance of material design and doping strategies in advancing renewable energy technologies.