Kinetics of light-driven oxygen evolution at α-Fe2O3 electrodes

5 The kinetics of light-driven oxygen evolution at polycrystalline α-Fe2O3 layers prepared by aerosolassisted chemical vapour deposition has been studied using intensity modulated photocurrent spectroscopy (IMPS). Analysis of the frequency-dependent IMPS response gives information about the competition between the 4-electron oxidation of water by photogenerated holes and losses due to electron-hole recombination via surface states. The very slow kinetics of oxygen evolution indicates the 10 presence of a kinetic bottleneck in the overall process. Surface treatment of the α-Fe2O3 with dilute cobalt nitrate solution leads to a remarkable improvement in the photocurrent response, but contrary to expectation, the results of this study show that this is not due to catalysis of hole transfer but is instead the consequence of almost complete suppression of surface recombination.