A series of Co3O4 catalysts was prepared by ammonia (Co-AP) and oxalate (Co-OP) precipitation,solgel (Co-SG),and urea hydrothermal (Co-UH) methods,and their physicochemical properties were characterised by numerous techniques including X-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscopy (TEM),nitrogen sorption,X-ray photoelectron spectroscopy (XPS),temperature-programmed reduction of H2 (H2-TPR),temperature-programmed desorption of O2 (O2-TPD),and temperature-programmed desorption of NH3 (NH3-TPD).The catalytic activity of each catalyst was estimated for the catalytic combustion of vinyl chloride (VC) emissions.The crystallite size of the Co3O4 catalyst was found to be well correlated with the amounts of surface-adsorbed oxygen species and number of acid sites on the catalyst surface,and consequently,determined several physicochemical properties of the catalyst.Of the catalysts studied here,the Co-AP catalyst exhibits the smallest crystallite size,which increases the specific surface area and the concentration of Co2+ on the catalyst surface.This,in turn,enhances the redox property,oxygen mobility,and the number of acid sites associated with the Co-AP catalyst.In fact,the Co-AP catalyst exhibits the best catalytic activity for VC combustion at 360 ℃ and does not produce any chlorinated by-products.