Heterojunction α‐Fe₂O₃/ZnO Films with Enhanced Photocatalytic Properties Grown by Aerosol‐Assisted Chemical Vapour Deposition

Type I heterojunction films of α‐Fe 2 O 3 /ZnO are reported here as a non‐titania based photocatalyst, which shows remarkable enhancement in the photocatalytic properties towards stearic acid degradation under UVA‐light exposure ( λ =365 nm), with a quantum efficiency of ξ =4.42±1.54×10 −4 molecules degraded/photon, which was about 16 times greater than that of α‐Fe 2 O 3 , and 2.5 times greater than that of ZnO. Considering that the degradation of stearic acid requires 104 electron transfers for each molecule, this represents an overall quantum efficiency of 4.60 % for the α‐Fe 2 O 3 /ZnO heterojunction. Time‐resolved transient absorption spectroscopy (TAS) revealed the charge‐carrier behaviour responsible for this increase in activity. Photogenerated electrons, formed in the ZnO layer, were transferred into the α‐Fe 2 O 3 layer on the pre‐μs timescale, which reduced electron–hole recombination. This increased the lifetime of photogenerated holes formed in ZnO, which oxidise stearic acid. The heterojunction α‐Fe 2 O 3 /ZnO films grown herein show potential environmental applications as coatings for self‐cleaning windows and surfaces.