Solar water splitting with nanostructured hematite: the role of oxygen vacancy

Surface defect engineering has shown to be an effective way to prepare cheap and efficient photoanode. In this study, oxygen vacancies are introduced to the hematite photoanode by a stepped atmosphere calcination with varied duration. The property of oxygen vacancies is verified by XRD, TEM, XPS and EPR analysis. With this facile treatment, the solar water splitting performance has been investigated. The enhanced photocurrent is about 1.96 mA cm −2 at 1.23 V RHE for the photoanode after 1.5 h calcination, which can keep constant even after 10 h illumination. Further study reveals that the maximum IPCE value of the photoanode reaches 56.5%. The creation of oxygen vacancies can lower the corresponding band gap for about 0.1 eV, which enhances the light absorption performance at the wavelength range from 750 to 620 nm. This photoanode displays the shortest charge transfer duration about 0.919 ms and the highest DC photocurrent about 597.13 × 10 –8 mA cm −2 based on IMPS measurement. The electronic property and interfacial resistance of the photoanode are also characterized by Mott–Schottky and EIS measurement. The corresponding detailed mechanism is discussed in this paper. Graphical abstract Schematic diagram and summary of the mechanism of oxygen vacancies introduced to the surface of α-Fe 2 O 3 photoanode during solar water splitting.