Photoanodic response of hematite electrode to citric acid in aqueous solution

The iron oxide film was prepared by the current pulse deposition on a titanium substrate in aqueous solution of 10 mM FeCl2-0.15 M NaCl under O2 bubbling. The hematite structure of the deposited film after heat treatment under air was confirmed by the measurement of XRD and Raman spectrum. The Mott-Schottky plots of the hematite electrode/aqueous Na2SO4 solution showed the flat-band potential of − 0.57 V vs. Ag/AgCl and the carrier density of 1.35 × 1018 cm− 3 for the hematite electrode. A marked increase in photocurrent was observed on the hematite electrode in the presence of citric acid under irradiation of visible light with wavelength of 490 nm. The HPLC analysis indicated the occurrence of oxidation of citric acid to acetonedicarboxylic acid with the current efficiency of 100% in this photoanodic process.