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

AbstractWith the precursor solution prepared by ZnSO4·7H2O and MOH (M = Li, Na or K), ZnO nanocrystals single doped with Li, Na, K and codoped with Na and K were prepared via a simple hydrothermal method. Their morphologies and structures were characterized by SEM, XRD, ICP, XPS and ultraviolet-visible spectrophotometer methods. It is found that the crystal morphology changes from the short bar shape to the long strip shape; Li+ is likely easier than Na+ and K+ to enter into the lattice to replace Zn2+ and inhibits the growth of positive polar plane while promotes the growth of negative one of ZnO in hydrothermal environment, leading to the morphology of short bars; K+ is easier than Li+ and Na+ to promote the two-dimensional nucleation and accelerate the axial growth of ZnO, leading to the morphology of long strips; Na+ and K+ have the obvious synergistic effect to facilitate the access to the lattice of ZnO. Experimental result of photocatalytic degradation of methylene blue shows that the ratio I of in...