Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (2): 543-550.doi: 10.3866/PKU.WHXB201511194

• ARTICLE • Previous Articles     Next Articles

Controllable Modulation of Morphology and Photocatalytic Performance of ZnO Nanomaterials via pH Adjustment

Hai-Feng HU1,2,Tao HE1,*()   

  1. 1 CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, P. R. China
    2 University of Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2015-10-14 Published:2016-01-30
  • Contact: Tao HE E-mail:het@nanoctr.cn
  • Supported by:
    the International Cooperation Department of Ministry of Science and Technology of China(2015DFG62610)

Abstract:

ZnO microstructures and nanostructures with controlled-morphology were synthesized by the hydrothermal method. All samples were prepared using precursors at different pH values and then annealed at 500 ℃ for 2 h. The samples were characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), and BET specific surface area measurement. All samples were confirmed by XRD to be wurtzite ZnO. As the pH value of the precursor increased, sheet-like ZnO disappeared and rod-like ZnO was produced. The major surfaces of sheet-like and rod-like ZnO were polar and nonpolar crystal faces, respectively. At pH 6.5, Cl- was adsorbed onto the (002) polar face and inhibited the growth along the polar crystal face ({Zn2+}crystal surface). A microporous sheet ZnO was formed by annealing the obtained sheet-like Zn5(OH)8Cl2·H2O. When OH- was added into the precursor, Zn(OH)42- was generated via coordination with Zn2+, which was adsorbed onto the (002) polar face and promoted growth along the polar crystal face. Rod-like ZnO was thus produced. The obtained ZnO could photocatalytically reduce CO2 under illumination. Sheet-like ZnO exhibited better photocatalytic performance than rod-like ZnO. This may be because the polar crystal face shows better photocatalytic activity than the unpolar crystal face.

Key words: ZnO, pH value, Hydrothermal process, Morphology, Photoreduction of CO2

MSC2000: 

  • O649