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NiFe2O4 nanoparticles with a high concentration of oxygen vacancies were synthesized via a solvothermal route. The morphology and oxygen vacancies of the catalyst was changed by adjusting the ratio of ethylene glycol (EG) in the mixture solvent. Water was used as a hydrogen source, the thermal catalytic performance of NiFe2O4 was up to 357.6 μmol g−1 of CH4 evolution under low temperature conditions. These findings may further broaden the horizon for CO2 reduction using the oxygen nonstoichiometry strategy.

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.