Intelligent Hydrated-Sulfate Template Assisted Preparation of Nanoporous TiO₂ Spheres and Their Visible-Light Application

Hydrated metal sulfates (MSO(4)·xH(2)O, M = Zn, Fe, Co, Mg, etc.) were proposed to be intelligent templates to solvothermally synthesize nanoporous TiO(2) spheres with tunable chamber structures from hollow to solid and hybrid compositions. During the reaction, hydrated sulfate serves simultaneously as spherical template, water supplier, and composition controller, and it can be easily removed by washing. The as-prepared anatase TiO(2) spheres were evidenced to contain highly crystallized TiO(2) nanocrystals hybridized with a small amount of metal oxide from the hydrated sulfate. The formation mechanism of the hollow spheres involves the self-conglobation of hydrated sulfate, the hydrolysis of tetrabutyl titanate on the spherical templates, and the subsequent process of solvothermal crystallization. The proposed hydrated-sulfate assisted solvothermal (HAS) strategy was demonstrated to be widely applicable to various systems. When applied to visible-light photocatalysis, the hybrid TiO(2) spheres exhibit excellent photocatalytic performance, benefiting from the reduced charge recombination rate contributed by the heterojunctions of TiO(2) and the hybridized metal oxides.