Hydrogen production from photocatalytic water splitting over mesoporous-assembled SrTiO 3 nanocrystal-based photocatalysts

Abstract

Mesoporous-assembled SrTiO 3 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 SrTiO 3 nanocrystal-based photocatalysts with various hole scavengers: methanol, ethanol, 2-propanol, d-glucose, and Na 2SO 3, was investigated. The pristine mesoporous-assembled SrTiO 3 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 SrTiO 3 and commercial TiO 2 (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 SrTiO 3 photocatalysts. The Pt co-catalyst enhances the visible light harvesting ability of the mesoporous-assembled SrTiO 3 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 SrTiO 3 photocatalyst provided the highest photocatalytic activity, with hydrogen production rates (from 50 vol.% methanol aqueous solution systems) of 276 and 188 μmol h −1 g cat −1 and quantum efficiencies of 1.9 and 0.9% under UV and visible light irradiation, respectively.