Growth and Photocatalytic Activities of Porous ZnO/TiO2 Composite Microspheres with Crystalline–Amorphous Phase Boundary

Abstract

Mesoporous ZnO/TiO2 composites with the morphology of yolk-shell microspheres were synthesized via one-step solvothermal method. Modifying crystalline TiO2 microspheres with amorphous ZnO led to the enhancement of photocatalytic activity for both H2 evolution and degradation of organic dyes. Such improvement was mainly attributed to the heterostructure constructed between amorphous ZnO and crystalline TiO2. The mechanism of the growth for such heterostructural microspheres was discussed. The modulation of electronic structure and tuning of the atomic packing mode, along with its yolk-shell structure, would generate large quantities of unsaturated sites, leading to the much accessible adsorption of reactants and accelerating the surface reactions on the mixed phases. Besides, the efficient separation of photogenerated charges was facilitated by their appropriate interfacial band structures between ZnO and TiO2. Such synergetic effect resulted in the improvement of photocatalytic activities, and it provided new routes to better utilize amorphous materials in solar energy conversion. Favorable photocatalytic activity is achieved on ZnO/TiO2 composite microspheres by constructing amorphous/crystalline phase boundary with the optimal component percentage and porosity.