Photocatalytic hydrogen evolution from water over Pt/N-doped titania under visible light irradiation

Abstract

To date, there have been a multitude of studies on the production of hydrogen from direct water splitting using the most investigated semiconductor photocatalyst, titania (TiO2), because hydrogen has been considered as a cleanburning fuel. Moreover, this process takes advantage of the utilization of available and abundant resources, water and sunlight, which is believed to be a sustainable source of future energy supply. However, TiO2-composed systems require some modifications in order to improve the photocatalytic activity under visible light, which is the main portion of sunlight exposing the earth surface, such as anion doping of TiO2. In this study, the preparation of N-doped mesoporous TiO2 and N-doped non-mesoporous commercial TiO2, Degussa P-25, prepared at different N-doping content and calcination temperatures, as well as the effect of Pt loading, were investigated for photocatalyic H2 evolution under visible light irradiation. It was experimentally found that N-doped mesoporous TiO2, prepared at a urea:TiO2 molar ratio of 1:1 and a calcination temperature of 250C exhibited the highest efficiency. For the N-doped Degussa P-25, the preparation condition of the molar ratio of 0.5:1 and the temperature of 250C was the best for H2 evolution, but still less photocatalytically active than such the N-doped mesoporous TiO2 prepared at the optimum condition. Pt loading onto the N-doped mesoporous TiO2 via incipient wetness impregnation method was performed to improve the photocatalytic activity, exhibiting the optimum Pt loading content of 1.3 wt%