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

Fe2O3-SnO2 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(NO3)(3) center dot 9H(2)O, SnCl4 center dot 5H(2)O, H2O, CH3COCH2COCH3, and CH3OC2H4OH. The photoanodic properties were studied in a three-electrode cell with an aqueous buffer solution of pH = 7 as the supporting electrolyte. The Fe2O3-SnO2 films of r(sn) = 0-0.25 comprised hematite phase and exhibited photoresponse under the UV and visible light. The photoanodic response of the alpha-Fe2O3 film was enhanced by doping with Sn4+; 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 Fe2O3-TiO2 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.