Defect-enhanced Photocatalytic Activity of ZnO Micro/nanostructures

ZnO micro/nanocrystals with controlled oxygen defects are successfully prepared through annealing precursors obtained via a simple solvothermal method. The size and surface defects of the as-synthesized ZnO micro/nanocrystals increase with the solvent volume ratio of water/ethanol increasing; the BET surface areas of the corresponding samples decrease during these processes; photoluminescence reveals that the type and concentration of surface defects (oxygen vacancy and interstitial oxygen) are quite different for the samples prepared via different solvent volume ratio of water/ethanol. In addition, it is found that the photocatalytic activity of the synthesized ZnO nanocrystals is mainly dependent on the concentration of surface defects. The sample with more surface defects exhibits higher photocatalytic activity toward the degradation of methylene blue (MB). The possible photocatalytic mechanism is discussed in detail.