Preparation of nano-ZnO supported on porous carbon and the growth mechanism

A novel kind of porous carbon embedding ZnO nano-particles has been prepared by pyrolysis of poly vinyl alcohol (PVA) and ZnCl2 mixture coated on glass fiber mats. The structure of the composite was investigated through scanning electron microscopy, X-ray powder diffraction, X-ray energy spectrum analysis, N2 adsorption at 77 K and thermogravimetry analysis. The results indicate that the pyrolysis time is the key factor that controls the morphology and size of ZnO particles growing in carbonous materials. Various nanostructures, including zinc hydroxide chloride (ZHC) lamellae-packed ellipsoid particles, hexagonal pencil-like ZnO nanorods, oriented ZnO nanorods array, and ZnO microrods sized range of 30 nm–3 μm could be prepared by controlling the pyrolysis time from 30 to 180 min. Specific surface areas of carbon supports were in range of 380–630 m2/g. The growth process of nano-crystal of ZnO is believed to undergo the conversion of ZnCl2 to ZHC, and then the decomposition of ZHC to ZnO while they were heated at 450 °C.