H2 evolution from an aqueous methanol solution on SrTiO3 photocatalysts codoped with chromium and tantalum ions under visible light irradiation

SrTiO3 photocatalysts doped with chromium ions showed photocatalytic activities for H2 evolution from an aqueous methanol solution under visible light irradiation. However, it had a long induction period. Codoping of niobium or tantalum ions with chromium ions shortened the induction period, and increased the photocatalytic activities in respect of the H2 evolution. The photocatalytic activities of chromium- and chromium/tantalum-doped SrTiO3 were improved when they were pretreated at 773 K in the hydrogen reduction atmosphere. Codoping of tantalum ions suppressed the formation of Cr6+ ions and oxygen defects which would work as nonradiative recombination centers between photogenerated electrons and holes, resulting in the shortening of induction periods and the improvement of photocatalytic activities.