The role of iron oxide in the highly effective Fe-modified Co3O4catalyst for low-temperature CO oxidation

Abstract

A series of iron modified cobalt oxide catalysts (Fe_aCo_bO_x (b : a = M_Co : M_Fe, 10 < x < 15)) were prepared by a co-precipitation method, characterized by nitrogen adsorption–desorption, XRD, Raman spectroscopy, XPS, H₂-temperature programmed reduction, CO-temperature-programmed desorption, O₂-temperature-programmed desorption and time-resolved CO titration, and their catalytic activities for CO oxidation were evaluated. When Co : Fe is 8 : 2 (mol), the Fe₂Co₈O_x catalyst exhibits a very high catalytic activity, in which CO can be completely converted to CO₂ at −80 °C. The results show that the addition of Fe to Co₃O₄ can increase its surface area and inhibit the agglomeration of iron oxide, improve the reduction behaviour of Co₃O₄, optimize the ratio of Co³⁺ : Co²⁺ on the catalyst surface, and promote CO adsorption and CO₂ desorption on the catalyst surface. The oxygen species on Fe₂Co₈O_x are more active than those on Co₃O₄, and when the feed gas is lacking in oxygen the lattice oxygen of Fe₂Co₈O_x can easily overflow to the surface to participate in the oxidation of CO.