Role of ZnO morphology in its reduction and photocatalysis

Hydrogen-treated ZnO, which is a promising photocatalyst with enhanced visible light absorption, has recently attracted much attention. As an important property, morphology of a nanocrystal can significantly influence its reactivity and catalytic performance, but limited effort has been made to evaluate the morphological effect of ZnO on its reduction. Herein, typical one-dimensional scale-like ZnO (1D ZnO) and three-dimensional flower-like ZnO (3D ZnO) were successfully synthesized and exploited to demonstrate the important role of ZnO morphology in its reduction and photocatalytic dye-degradation. It was found that the hydrogen-treatment of 1D ZnO and 3D ZnO resulted in different changes of color, chemical states, and photocatalytic performance. Hydrogen treated 1D ZnO and 3D ZnO exhibited 120 and 400% increase of photocurrent under visible light irradiation, respectively, indicating that the enhancement is 4 times higher for 3D H-ZnO than for 1D H-ZnO. Furthermore, the hydrogen treatment enhanced the degradation of methylene blue by 500% for 3D ZnO and 130% for 1D ZnO, namely, 3D ZnO achieved 3 times larger enhancement in degradation efficiency than 1D ZnO after H-2-treatment.