Photocatalytic Reduction of CO 2 by ZnO Micro/nanomaterials with Different Morphologies and Ratios of {0001} Facets.

ZnO microspheres, ZnO microflowers and ZnO nanorods are successfully synthesized via a convenient solvothermal method in distilled water-ethanol mixed medium. The as-prepared ZnO micro/nanomaterials are characterized by XRD, SEM, TEM, HRTEM, XPS, BET, and UV-Vis. The morphologies and exposed facets of the ZnO micro/nanomaterials can be controlled by simply changing the volume ratio of distilled water to ethanol, and their formation mechanisms are also proposed. In addition, the photocatalytic activities of the ZnO samples are investigated towards the photoreduction of CO2 to CO. It is found that ZnO nanorods with high ratio of {0001} facets and large surface areas possess higher CO formation rate (3.814 μmol g-1 h-1 ) in comparison with ZnO microspheres and ZnO microflowers (3.357 and 1.627 μmol g-1 h-1 , respectively). The results can not only provide an important indication about the influence of the {0001} facets on the activity of CO2 photoreduction over ZnO, but also demonstrate a strategy for tuning the CO2 photoreduction performance by tailoring the surface structures of ZnO micro/nanomaterials.