STABILITY AND PHOTORESPONSE OF NANOCRYSTELLINE N-TIO2 AND N-TIO2 MN2O3 THIN-FILM ELECTRODES DURING WATER-SPLITTING REACTIONS/

The bare n-TiO2 film electrode was found to be unstable during water s plitting reactions under illumination of light. Significant improvemen t of stability was observed for Mn2O3 covered n-TiO2, i.e., n-TiO2/Mn2 O3, thin film electrodes. The Mn2O3, layer also enhanced the rate of o xygen evolution instead of H2O2 formation, due to its catalytic effect . The highest photoresponse was found with an n-TiO2 film prepared at 850 degrees C for 13 min by thermal oxidation. The bandgap energy of b oth n-TiO2 and n-TiO2/Mn2O3 films was found to be 2.85 eV. X-ray diffr action results indicate rutile structure for the n-TiO2 film. The flat band potential of the n-TiO2 film was found to be -1.13 V/saturated ca lomel electrode from the intercept of the Mott-Schottky plot. The high est potential-assisted photoconversion efficiencies, 5.1 and 4.1%, and the corresponding practical photoconversion efficiencies, 2.0 and 1.6 %, were obtained for water splitting by the n-TiO2 and n-TiO2/Mn2O3 fi lm electrodes, respectively.