Effect of gamma-irradiation on surface and catalytic properties of Co3O4 and NiO catalysts

Abstract

The effects of g-irradiation (0.2-1.6 MGy) on the particle size, specific surface area and catalytic activity of Co3O4 and NiO solids were investigated. The investigated solids were prepared by heat treatment of cobalt carbonate at 500 and 700 °C and basic nickel carbonate at 400 °C. The techniques employed were XRD, nitrogen adsorption at -196 °C and decomposition of H2O2 at 30-50 °C. The results showed that g-irradiation resulted in a small decrease in the particle size of the investigated solids and effected a progressive increase in their specific surface areas. On the other hand, the exposure of Co3O4 and NiO catalysts to a dose of 0.2 MGy resulted in a significant decrease in their catalytic activities, which suffered further progressive decrease upon increasing the doses up to 1.6 MGy. Gamma-irradiation did not modify the activation energy of the catalyzed reaction but decreased the concentration of catalytically active sites without changing their energetic nature. These results were discussed in terms of splitting of the particles of the treated solids and removal of chemisorbed species present in nonstoichiometric cobalt and nickel oxides.