XPS characterization and photoelectrochemical behaviour of p-type 3C-SiC films on p-Si substrates for solar water splitting

The electrochemical (EC) properties of single-crystalline p-type 3C-SiC films on p-Si substrates were investigated as electrodes in H2SO4 aqueous solutions in dark and under white light illumination. Before EC tests, the SiC films were etched by HF solution and aqua-regia–HF solution, respectively, and then investigated by x-ray photoelectron spectroscopy (XPS) including one untreated SiC sample. After EC tests, XPS was also applied to investigate the surface chemical state changes. The EC measurements indicate that the p-type 3C-SiC films on p-Si substrates can generate a cathodic photocurrent as the photocathode, which corresponds to hydrogen production, and generate an anodic photocurrent as the photoanode, which corresponds to oxygen evolution. XPS shows the surface of all the SiC films was oxidized due to anodic oxidation applied by a positive bias during the EC test, which indicates the formation of silicon oxides, CO2 or CO and carbonates.