Synthesis and characterization of silica-supported cobalt nanocatalysts using electrostatic adsorption

Strong electrostatic adsorption (SEA), a simple yet logical method, was employed to synthesize cobalt catalysts supported on silica. Mono-dispersed non-porous silica sphere was synthesized as a model support using modified Stöber method. Point of zero charge (PZC) of silica synthesized in-house was determined using equilibrium pH at high oxide loading (EpHL) method. Cobalt uptake versus pH was studied to determine the optimum pH. High cobalt uptake at basic pH and low cobalt uptake at acidic pH indicates electrostatic interaction between the cobalt complexes in the precursor solution and the hydroxyl group on the support’s surface. Catalysts prepared at optimum pH were characterized using TPR, XPS and TEM. TPR shows reduction peak at high temperature (702°C) indicating strong interaction between cobalt and silica support. XPS shows presence of Co2+ species on the surface, but no cobalt-ammine complex was detected. TEM images show fairly well dispersed cobalt particles on the support. SEA was deemed a suitable method to prepare supported cobalt catalysts.