Abstract: A method of synthesizing TiO2/Co3O4 core-shell photocatalysts is provided. The method includes preparing SiO2 hollow nanospheres via sol-gel synthesis in the presence of a triblock copolymer surfactant and a cationic surfactant; adding titanium sec-butoxide to a solution containing the SiO2 hollow nanospheres to provide a first combined sample; calcinating the first combined sample to provide hollow mesoporous TiO2 nanospheres; adding cobalt nitrate to a solution comprising the hollow mesoporous TiO2 nanospheres to provide a second combined sample; and calcinating the second combined sample to provide TiO2/Co3O4 core-shell photocatalysts. Methods of producing hydrogen by water-splitting using TiO2/Co3O4 core-shell photocatalysts are also provided. Such methods include photodepositing platinum onto the photocatalysts during the reaction.