Electrodeposition of p-type Cu2O on n-type TiO2 nanosheet arrays for enhanced photoelectrochemical water splitting

Abstract

This study synthesized p-type Cu₂O using an electrodeposition method and firmly attached it to TiO₂ nanosheets based on fluorine-doped tin oxide (FTO) substrates, forming a dense film that serves directly as a photoanode for photoelectrochemical (PEC) water splitting. Characterization techniques such as XRD, SEM, XPS, and UV–Vis confirmed the successful deposition of Cu₂O on the TiO₂ nanosheets, forming a p-n heterojunction structure. The incorporation of Cu₂O effectively broadened the light absorption range of TiO₂, with a cut-off wavelength red-shifting to 537 nm, enabling it to absorb more visible light. Photoelectrochemical tests showed that under illuminated unbiased conditions, the photocurrent density of Cu₂O-TiO₂ reached 0.3 mA/cm², which is 7.5 times that of TiO₂. After applying a small bias (0.5 V), the photocurrent density further increased to 2.1 mA/cm², 5.2 times that under unbiased conditions, indicating that the introduction of electricity effectively accelerated the separation efficiency of photo-generated carriers. The Cu₂O-TiO₂ heterojunction exhibited significantly higher photocurrent density (measured by LSV) and charge transfer efficiency (evaluated by EIS) than pure TiO₂. This research provides new insights for PEC water splitting technology and serves as a reference for designing high-performance photocatalysts.