Morphology-Dependent Properties of MnO_<i>x</i>/ZrO₂–CeO₂ Nanostructures for the Selective Catalytic Reduction of NO with NH₃

Abstract

The morphology effect of ZrO2–CeO2 on the performance of MnOx/ZrO2–CeO2 catalyst for the selective catalytic reduction of NO with ammonia was investigated. The catalytic tests showed that the MnOx/ZrO2–CeO2 nanorods achieved significantly higher NO conversions than the nanocubes and nanopolyhedra. The catalytic tests also showed that the MnOx/ZrO2–CeO2 nanorods achieved a significantly higher rate constant with respect to NO conversion than that of the nanocubes and nanopolyhedra. On the nanorods, the apparent activation energy is 25 kJ mol–1, which was much lower than the values of nanocubes and nanopolyhedra (42 and 43 kJ mol–1). The high resolution transmission electron microscopy showed that the nanorods predominately exposed {110} and {100} planes. It was demonstrated that the ZrO2–CeO2 nanorods had a strong interaction with MnOx species, which resulted in great superiority for the selective catalytic reduction of NO. The excellent catalytic activity of the MnOx/ZrO2–CeO2 nanorods should be attributed to the Mn4+ species, adsorbed surface oxygen and oxygen vacancies which are associated with their exposed {110} and {100} planes.