Photoelectrochemical Properties of Fe2O3−SnO2 Films Prepared by Sol−Gel Method

Fe 2 O 3 −SnO 2 coating films of various Sn/(Fe + Sn) mole ratios, r Sn, were prepared by dip-coating on Nesa silica glass substrates from the solutions consisting of Fe(NO 3 ) 3 ·9H 2 O, SnCl 4 ·5H 2 O, H 2 O, CH 3 COCH 2 COCH 3, and CH 3 OC 2 H 4 OH. The photoanodic properties were studied in a three-electrode cell with an aqueous buffer solution of pH = 7 as the supporting electrolyte. The Fe 2 O 3 −SnO 2 films of r Sn = 0−0.25 comprised hematite phase and exhibited photoresponse under the UV and visible light. The photoanodic response of the α-Fe 2 O 3 film was enhanced by doping with Sn 4+; the film of r Sn = 0.1 exhibited the maximum IPCE (incident photon-to-current efficiency) of 26.9% and 8.6% at the wavelengths of 350 and 425 nm, respectively, which were higher than those of the Fe 2 O 3 −TiO 2 film of Ti/(Fe + Ti) = 0.1 prepared by similar process. IPCE decreased with increasing r Sn from 0.1 to 0.25. The films of r Sn ≥ 0.5 comprised rutile phase without hematite phase, showing very low IPCE.