Design and fabrication of an α-Fe2O3/TiO2/Si 3D hierarchical photoanode for improved photoelectrochemical water splitting

Ordered hierarchical structured films are considered promising photoanodes for high-performance water-splitting because of their large surface area for light absorption and excellent charge transfer process. In this paper, a novel hierarchical structured photoanode based on growing TiO2 on a Si nanowire substrate and coupling with Fe2O3 nanothorns was designed and fabricated via a simple method to obtain photoelectrochemical (PEC) properties. The Fe2O3/TiO2/Si nanowire arrays (NWs) were characterized in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis spectra. The 3D Fe2O3/TiO2/Si hierarchical photoanode exhibited a photocurrent density of 3.5 mA cm−2 at a bias potential of 1.23 V (vs. RHE), which is approximately 87.5 times higher than that of the Si nanowire array (NW) photoanode. The measurement results showed that the improved PEC performance could be attributed to the synergistic effect of the large surface area, low charge transfer resistance, and high charge separation in the hierarchical structure.