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 10mM FeCl2–0.15M 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 −0.57V vs. Ag/AgCl and the carrier density of 1.35×1018cm−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 490nm. The HPLC analysis indicated the occurrence of oxidation of citric acid to acetonedicarboxylic acid with the current efficiency of 100% in this photoanodic process. •The hematite film was prepared by current pulse method in aqueous NaCl solution containing Fe(Cl)2 under O2 bubbling and heat treatment in air.•The hematite photoelectrode showed a marked increase in photocurrent in the presence of citric acid.•The photoanodic oxidation of citric acid to acetonedicarboxylic acid with the current efficiency of 100 % proceeded in the visible light irradiation.