Novel Mn–Cu-Containing CeO2 Nanopolyhedra for the Oxidation of CO and Diesel Soot (Part II): Effect of Oxygen Concentration on the Catalytic Activity

Abstract

In this work, ceria-based nanocatalysts mixed with copper and manganese were studied. All the catalysts were synthesized via the hydrothermal procedure. Four samples were prepared here denoted through the atomic ratios of the metals in the mixed oxide: Ce0.95Mn0.05, Ce0.95Cu0.05, Ce0.95Mn0.025Cu0.025 and CeO2. The samples were tested for the CO and soot oxidation reactions with different gas-phase oxygen concentrations (10, 1.0, 0.5 and 0.02 vol% O2). As a whole, the most promising catalysts for the CO oxidation reaction are the Ce0.95Cu0.05 and Ce0.95Mn0.025Cu0.025 samples. Indeed, the presence of Cu species in the solid enhances the surface redox mechanism for the CO oxidation. High vol% O2 values lead to competitive CO and O2 adsorption on the catalyst surface thus reducing the catalytic performances for binary and ternary oxides. On the other hand, the CO oxidation reaction over the CeO2 catalyst appears favored with 10 vol% O2. For the soot oxidation reaction, the most active catalyst (in terms of soot conversion %) is the CeO2 sample likely due to the unique feature of presenting well-defined and highly reactive nanocubic structures. Moreover, the presence of 10 vol% O2 in the mixture appears to be the best condition to oxidize the soot particles.