One-step preparation of hollow ZnO core/ZnS shell structures with enhanced photocatalytic properties

We report here a facile one-step strategy to prepare hollow ZnO core/ZnS shell structures by microwave irradiation. The growth mechanism of the hollow core/shell structures was investigated in detail. ZnO truncated hexagonal pyramids first form on as-grown precursor flakes and then evolve into ZnO hexagonal twin crystals, which subsequently grow up and dissolve internally. The hollowing progress is firstly controlled by the Kirkendall effect and then undergoes an Ostwald ripening process. Hollow structures and the formation of ZnO/ZnS heterostructure bring enhanced photocatalytic activities to ZnO core/ZnS shell structures. The formed ZnO/ZnS heterostructures also fill the surface defects of ZnO crystals and improve the stability of the photocatalysts by overcoming the photocorrosion effect of a single ZnO photocatalyst under UV light irradiation. Superoxide radicals (O-2(center dot-)) are the key active species in the photocatalytic system of degradation of p-chlorophenol over hollow ZnO core/ZnS shell structures. The photocatalysis process has been discussed and a possible mechanism also has been proposed. This work is helpful to controllably construct other hollow core/shell structures, develop ZnO-based photocatalysts without photocorrosion effect and further study the photocatalytic mechanism of similar systems.