Photocatalytic oxygen evolution on alpha-Fe2O3 films using Fe3+ ion as a sacrificial oxidizing agent

Photocatalytic oxygen evolution on alpha-Fe2O3 films was studied using the Fe3+ ion as a sacrificial oxidizing agent. The reaction conditions affecting the oxygen evolution rate, i.e. anion, Fe3+ concentration, pH, Fe3+/Fe2+ equilibrium concentration and dependence of irradiation wavelength, were investigated. The reaction rate increased with increase of both the Fe3+ ion concentration and the solution pH. Oxygen evolution ceased at an Fe3+:Fe2+ ion concentration ratio of 3:7-4:6. The reaction rate decreased rapidly for longer-wavelength irradiation (above around 400 nm), which is considerably shorter than the alpha-Fe2O3 bandgap of ca. 600 nm (2.1 eV).