Effect of the Composition of Ni x Co3–xO4 (x = 0–0.9) Oxides on Their Catalytic Activity in the Low-Temperature Reaction of N2O Decomposition

Abstract

The Ni x Co3–xO4 (x = 0–0.9) mixed oxides with a spinel structure modified with 2% Cs according to the Pechini method were prepared by coprecipitation from the solutions of nitrates with the use of (NH4)2CO3 as a precipitating agent. It was found that the catalytic activity of the samples in the reaction of nitrous oxide decomposition at temperatures of 150–400°C increased upon the partial replacement of cobalt cations by nickel cations. The most active samples were 2%Cs/Ni0.1Co2.9O4 and 2%Cs/Ni0.7Co2.3O4. With the use of X-ray diffraction analysis, it was found that an increase in the nickel content of the mixed oxide leads to the appearance of an impurity phase of nickel oxide and to an increase in its concentration in the samples. The results of temperature-programmed reduction and temperature-programmed desorption indicated that the introduction of nickel cations was accompanied by the appearance of weakly bound oxygen species in Ni–Co spinel; this can be the reason for an increase in their activity in the reaction of N2O decomposition.