Morphology-controlled synthesis of SrTiO3/TiO2 heterostructures and their photocatalytic performance for water splitting

Abstract

Different morphologies of SrTiO₃/TiO₂ heterostructures like nanocubes, nanoparticles, nanospheres, and nanofibers were synthesized via a facile hydrothermal process using TiO₂ as both a template and precursor in Sr(OH)₂ solution. Their structure, interface and composition can be rationally tailored by simply adjusting the Sr(OH)₂/TiO₂ (Sr/Ti) mole ratios and the morphology of SrTiO₃/TiO₂ heterostructures can be controlled easily using TiO₂ with different morphologies. A SrTiO₃ crystal thin layer was grown on an anatase TiO₂ substrate to fabricate a heterostructure interface contact between SrTiO₃ and TiO₂ and the lattice mismatch had an effect on the electrical transport properties. The SrTiO₃/TiO₂ heterostructures are beneficial for the fast separation of photogenerated electrons and holes so as to suppress the recombination of photogenerated electrons and holes at the interface of SrTiO₃ and TiO₂. Besides this, the different morphologies of the SrTiO₃/TiO₂ heterostructures allowing facile electron transfer, the hierarchical structure promoting mass transfer and allowing more light reflection and absorption, and the large specific surface area providing more reaction sites to facilitate the reactants to the desired oxidation places all together create a synergistic effect to improve the photocatalytic activity of the hierarchical SrTiO₃/TiO₂ heterostructures. Under the irradiation of UV light, in a water/methanol sacrificial reagent system, the SrTiO₃/TiO₂ NP heterostructures at a Sr/Ti mole ratio of 40% with the highest BET and smallest crystallite size achieve the highest photocatalytic activity generating 0.731 mmol of H₂. The SrTiO₃/TiO₂ heterostructures exhibit better photocatalytic activity by generating three times more H₂ than bare TiO₂ and pure SrTiO₃.