Hydrogen production from photocatalytic water splitting over mesoporous-assembled SrTiO3 nanocrystal-based photocatalysts

Mesoporous-assembled SrTiO3 nanocrystal-based photocatalysts were synthesized via the sol–gel method with the aid of a structure-directing surfactant. The photocatalytic water splitting activity for hydrogen production over the mesoporous-assembled SrTiO3 nanocrystal-based photocatalysts with various hole scavengers: methanol, ethanol, 2-propanol, d-glucose, and Na2SO3, was investigated. The pristine mesoporous-assembled SrTiO3 photocatalysts exhibited much higher photocatalytic activity in hydrogen production via the photocatalytic water splitting using methanol as the hole scavenger than both non-mesoporous-assembled commercial photocatalysts: commercial SrTiO3 and commercial TiO2 (Degussa P-25), even if their specific surface areas were lower than those of both commercial photocatalysts. These results point out that the mesoporous assembly of nanocrystals with high pore uniformity plays a significant role, affecting the photocatalytic hydrogen production activity of the SrTiO3 photocatalysts. The Pt co-catalyst enhances the visible light harvesting ability of the mesoporous-assembled SrTiO3 photocatalyst and behaves as the active site for proton reduction, leading to photocatalytic activity enhancement under both UV and visible light irradiation. Methanol provided the highest photocatalytic hydrogen production enhancement. An optimum Pt loading of 0.5 wt.% on the mesoporous-assembled SrTiO3 photocatalyst provided the highest photocatalytic activity, with hydrogen production rates (from 50 vol.% methanol aqueous solution systems) of 276 and 188 μmol h−1 gcat−1 and quantum efficiencies of 1.9 and 0.9% under UV and visible light irradiation, respectively.