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CuO/VO x /Ti 0.5 Sn 0.5 O 2 catalysts were prepared by an impregnation method and were tested on a NO þ CO model reaction. Both copper oxide and vanadium oxide can be highly dispersed on Ti 0.5 Sn 0.5 O 2 (denoted as TS, hereafter) support. The dispersed oxides form VÀOÀCu species when coexisting in the catalyst system. The formation of VÀOÀCu species renders the dispersed vanadium oxide aggregated and easier to be reduced; in contrast, the reduction temperature of dispersed copper oxide species is evidently higher than that without vanadium oxide (CuO/TS samples). The surface dispersed VÀOÀCu species are mainly the active component for the NO þ CO reaction. The activities of CuO/VO x /TS catalysts are highly dependent on the operating temperature and the amount of VÀOÀCu species. In the reaction atmosphere, NO molecules are adsorbed onto Cu 2þ sites, reduced V xþ (V 4þ or V 3þ ) sites, and even TS support, forming ÀNO and NO 3 À species. Adsorption of CO molecules proceeds only on Cu þ sites. The active species change with varying reaction temperature; hence, the NO þ CO reaction goes through different mechanisms at low and high temperatures over these catalysts.

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