Effects of different alkali metal ions on morphology and photocatalysis properties of ZnO crystals via hydrothermal method

摘要

With the precursor solution prepared by ZnSO_4·7H_2O and MOH (M = Li, Na or K), ZnO nanocrystalssingle doped with Li, Na, K and codoped with Na and K were prepared via a simple hydrothermalmethod. Their morphologies and structures were characterized by SEM, XRD, ICP, XPS and ultravioletvisiblespectrophotometer methods. It is found that the crystal morphology changes from the shortbar shape to the long strip shape; Li~+ is likely easier than Na~+ and K~+ to enter into the lattice to replaceZn~(2+) and inhibits the growth of positive polar plane while promotes the growth of negative one ofZnO in hydrothermal environment, leading to the morphology of short bars; K+ is easier than Li+ andNa~+ to promote the two-dimensional nucleation and accelerate the axial growth of ZnO, leading tothe morphology of long strips; Na~+ and K~+ have the obvious synergistic effect to facilitate the access tothe lattice of ZnO. Experimental result of photocatalytic degradation of methylene blue shows that theratio I of intensitiy of X-ray diffraction peak for (002) plane to that of (100) plane can reflect the relativearea proportion of plane (002) with strong photocatalytic activity, and the photocatalytic effect maybe better if the value of I is larger.