Photoelectrochemical properties of hematite thin film photoelectrodes prepared by reactive magnetron sputtering

Hematite with a band gap of 2.2eV is a potential candidate for photoelectrochemical hydrogen production utilizing solar energy. In this study, high-quality iron oxide(α-Fe ₂O ₃) films prepared by reactive-sputtering process are reported along with their structural characterization and application to water splitting. Pure iron target and argon carrier gas were used in the process. Hematite thin films were deposited on ITO glasses under various oxygen partial pressure ratios from 9%∼36% and substrate temperatures from 150 °C to 450 °C. The bulk properties of α-Fe ₂O ₃ were analysed by XRD, SEM, and UV/VIS spectrometer. The SEM images showed that the average grain sizes of the films decrease with oxygen partial pressure. Furthermore, the XRD results revealed that oxygen partial pressure and substrate temperature play an important role in preferred orientation of the crystallites. The hematite thin films prepared under lower temperature (150) and low oxygen partial pressure (P _O29%) exhibited dominant (300) peaks. On the other hand, (104) orientation was enhanced at higher temperature (450) in all oxygen partial ratios. The photocurrents and stability were measured in sodium hydroxide under the illumination of Xe light. A maximum photocurrent density of 4.9 mA/cm ² was observed in samples prepared at 450 substrate temperature and 18% oxygen partial pressure ratio, under 0.7V/SCE bias and 100 mW/cm ² illumination intensity.