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A novel heterojunction photocatalyst of TiO 2 -SrIn 2 O 4 is found to be active for hydrogen generation from water as well as for the degradation of methylene blue under sunlight type radiation. Photocatalytic activity for hydrogen generation increases with increase in SrIn 2 O 4 concentration and the optimum concentration is found to be 40% (by weight). The presence of a Pd co-catalyst enhances the photocatalytic activity and the catalyst is found to be stable after repeated cycles of photocatalysis experiments. A higher rate of degradation of methylene blue is observed when the composite is used as photocatalyst compared to pure TiO 2 and SrIn 2 O 4 . Detailed characterization of the composite revealed that TiO 2 exists as a dispersed phase on SrIn 2 O 4 and the particle size of TiO 2 and TiO 2 -SrIn 2 O 4 is around 20 nm and 15 nm, respectively. Photocurrent experiments show a relatively higher current output for the composite compared to pure TiO 2 . The enhanced photocatalytic activity of the composite is attributed to a synergistic effect of the increased lifetime of the charge carriers in the composite and increased surface area of the sample. The dispersion of TiO 2 nanoparticles on SrIn 2 O 4 results in the formation of heterojunctions between TiO 2 and SrIn 2 O 4 leading to efficient interfacial transfer of photogenerated electrons from TiO 2 to SrIn 2 O 4 and enhancing the lifetime of the charge carriers. The Pd co-catalyst enhances the activity of the composite further by increasing the availability of electrons in it and providing active sites for hydrogen evolution. Scheme 1 Schematic of the synthesis process of TiO 2 -SrIn 2 O 4 composite. 55540 | RSC Adv., 2014, 4, 55539-55547 This journal is

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