Effects of gamma-irradiation and Li₂O-doping on surface and catalytic properties of unloaded Co₃O₄ solid

Abstract

The effects of γ-irradiation (20–160 Mrad) and lithium oxide doping (0.75–6 mol%) on the surface and catalytic properties of unloaded Co₃O₄ solid have been investigated. The surface characteristics of various solids were determined from nitrogen adsorption isothems taken at −196 °C and their catalytic activities were measured by following the kinetics of CO-oxidation by O₂ at 100–150 °C using a static method. The results showed that γ-rays brough about a decrease of 21% inS _BET of Co₃O₄ due to widening of its pores and led also to a considerable increase in its catalytic activity. A maximum increase of 91% was observed upon exposure to a dose of 80 Mrad. Lithium oxide-doping at at 500 °C resulted in an increase of 150% inS _BET of treated solid without changing its mean pore radius. This treatment was also accompanied by an increase of about 50% in its catalytic activity measured at 150 °C. Gamma-irradiation and Li₂O-doping of unloaded Co₃O₄ did not change the magnitude of apparent activation energy of catalysis of CO-oxidation by O₂ but increased the concentration of catalytically active sites contributing in the catalytic process. In other words, γ-rays and lithium oxide doping did not alter the mechanism of catalytic oxidation of CO by O₂ over unloaded cobaltic oxide solid.