Influence of particle size and shape on the rate of hydrogen produced by Al‐doped SrTiO3 photocatalysts

Abstract Photocatalytic hydrogen production rates have been measured from Al‐doped SrTiO 3 with a range of controlled shapes and sizes using a high‐throughput parallelized and automated photochemical reactor. It is found that the photocatalytic reactivity is influenced by crystal shape and that crystals with a {1 1 0} to {1 0 0} surface area ratio between 1.3 and 1.8 yield more H 2 than crystals with other ratios. Crystals with a {1 1 0}/{1 0 0} surface area ratio of 1.8 generate hydrogen at 550 μmol h −1 g −1 at pH 7, whereas crystals with only {1 0 0} facets exposed generate hydrogen at 300 μmol h −1 g −1 under the same condition. It is likely that the surface area ratio provides the appropriate balance between the photoanodic reaction on the {1 1 0} surface and the photocathodic reaction on the {1 0 0} surface. In the size range of 250–450 nm, larger crystals produce hydrogen at a rate of 400 μmol h −1 g −1 at pH 7, whereas smaller crystals only produce 200 μmol h −1 g −1 , suggesting that the larger crystals reduce the rate of electron–hole recombination or back reaction and that the widths of the space charges within the crystal are comparable to the particle radius.