Hybrid microwave annealing-induced formation of an α-Fe2O3/ZnWO4 interface for photoelectrochemical water splitting and study of its charge transport mechanism

Abstract

The α-Fe₂O₃ photoanode is an efficient semiconductor material for photoelectrochemical (PEC) water oxidation due to its favorable bandgap, chemical stability, and natural abundance. However, the rapid recombination of photoexcited electrons (e⁻) and holes (h⁺) impedes the PEC efficiency. Herein, an α-Fe₂O₃/ZnWO₄ heterojunction photoanode was synthesized by combining hydrothermal and hybrid microwave annealing methods. The α-Fe₂O₃/ZnWO₄ heterojunction photoanode demonstrated a photocurrent density of 0.86 mA cm⁻² at 1.23 V vs. RHE, which is more than 2.2 times that of pure ZnWO₄ (0.06 mA cm⁻²) and the α-Fe₂O₃ photoanode (0.29 mA cm⁻²). In contrast, the α-Fe₂O₃/ZnWO₄ photoanode exhibited an improved ABPE value of 0.10% at 1.0 V vs. RHE. The significantly improved charge separation efficiency and reduced charge recombination were attributed to hole storage in a ZnWO₄ heterojunction layer.