Effect of Pr doping on catalytic properties of oxide ion conductor, Zr-Nd-O, for soot oxidation

Effects of incorporation of Pr into Zr-Nd oxides possessing high oxide ion conductivity on catalytic soot oxidation have been investigated. In carbon oxidation under isotopic oxygen flow, Pr doping facilitates desorption of active lattice oxygen via oxygen exchange reaction, and this improves the carbon oxidation rate. Redox reaction of incorporated Pr (Pr⁴⁺ to Pr³⁺) hardly occurs under both reductive and oxidative conditions. Pr doping presents mixed hole and oxide-ion conductivity, and the hole conduction becomes more dominant with increasing Pr content. Therefore, the generation of electron hole in the oxygen incorporation step and its recombining with electron in the oxygen desorption step seems to enhance the participation of active lattice oxygen in carbon oxidation and improve the catalytic oxidation performance.