Influence of the surface structure of a nickel oxide catalyst on the mechanism of the room-temperature oxidation of carbon monoxide

Abstract

The oxidation of carbon monoxide has been studied at 30 °C on a nickel oxide prepared by dehydration at 200 °C and 10 −6 torr of a pure nickel hydroxide [NiO(200)], on a nickel oxide prepared at 250 °C [NiO(250)], and on nickel oxides with lithium or gallium additions [NiO(Li)(250) and NiO(Ga)(250)]. The slowest step of the overall reaction, in the case of NiO(250) and NiO(Ga) (250), is the interaction between adsorbed oxygen and carbon monoxide, whereas, in the case of NiO(200) and NiO(Li)(250), the slowest step is the interaction between CO 3 post−(ads) ions and carbon monoxide. It is concluded that the catalytic activity in the oxidation of carbon monoxide, which follows the sequence NiO(200) < NiO(Li)(250) < NiO(Ga)(250) ⩽ NiO(250), is related rather to the surface defect structure and to the energy distribution of the surface adsorption sites than to the electronic structure of the catalysts.