CO oxidation over Mn-Ce mixed oxides prepared by a simple redox method

In this study, Mn_xCe_(1−x) mixed oxides (x = 0, 0.25, 0.50, 0.75, and 1.00) were synthesized using a straightforward redox method, and the effect of the Mn-Ce composition on the total oxidation of carbon monoxide (CO) was examined. Under standard reaction conditions of 1% CO and 4% O₂, the light-off temperatures (T_50%), which indicate the temperature at which 50% of the CO conversion occurs, of Mn-Ce mixed oxide increased in the sequence: 0.25 < 0.50 < 0.75 < 1.00 (MnO₂) < 0 (CeO₂). Although Mn_0.25Ce_0.75 stands out for its superior catalytic performance, this efficiency notably diminishes when CO₂ and H₂O vapors are introduced into the reactants. This decline is attributed to the competitive adsorption of CO₂ and H₂O on the active sites, which impedes the oxidation of CO. Various techniques have been employed to understand the physicochemical properties of Mn-Ce mixed oxides. The analysis revealed that incorporating an appropriate amount of Mn into Ce yielded a substantial quantity of labile oxygen species, enhancing the reducibility of the system, thereby improving its catalytic performance. Although improving H₂O resistance is essential, Mn-Ce mixed oxides present a promising alternative to noble-metal-based oxidation catalysts.