Influence of synthesis conditions on the photocatalytic activity of mesoporous Ni doped SrTiO3/TiO2 heterostructure for H2 production under solar light irradiation

Ni doped SrTiO3/TiO2 (NSTO-2) nanocomposites synthesized by ultrasonic assisted hydrothermal method showed 2.3 times higher rate of H2 production than the same material synthesized by simple hydrothermal method (NSTO-1) under solar light irradiation. In ultrasonic assisted hydrothermal method, sonication played a significant role in the formation of well dispersed nanoparticles with decreased particle size for NSTO-2. On the attempt of the removal of SrCO3, the assynthesized NSTO-2 washed with acid first and then calcined at 400 °C leached out all the Sr2+ ions and resulted only Ni3+ doped anatase TiO2 (NSTO-2(BC)). Whereas NSTO-2 calcined first at 400 °C and then washed with acid was found to be stable and resulted Ni doped SrTiO3/TiO2 heterostructure (NSTO-2(AC)), this results supported the Ostwald ripening mechanism for the formation of SrTiO3/TiO2 heterojunction on calcination. XRD results revealed the formation of both anatase TiO2 and SrTiO3 for all the synthesized materials except for NSTO-2(BC). TEM images also showed the heterostructured SrTiO3/TiO2 interface, which played an important role in the suppression of electron-hole recombination and also the mesopores of about 10 nm built by the nanoscale porewalls composed of TiO2 and SrTiO3 lattice. Ni loading on SrTiO3/TiO2 extended the light absorption edge to visible light region, which was revealed by UV–vis diffuse reflectance spectra. N2 adsorption-desorption study showed the mesoporosity for all the materials with the pore diameter of about 10 nm. The charge transfer efficiency of NSTO-2(AC) was significantly improved by the presence of the SrTiO3/TiO2 heterojunction, mesorporous structure and also by the elimination of e−/h+ recombination centers by acid wash, hence NSTO-2(AC) showed the enhanced H2 production of about 3750 μmol h−1gcat−1 than other reported SrTiO3/TiO2 based catalysts under direct solar light irradiation.