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

Abstract

Photocatalytic oxygen evolution on α-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 α-Fe₂O₃ bandgap of ca. 600 nm (2.1 eV).