Ir/CeO2 Catalysts: Characterization and Performance for CO Oxidation

A series of Ir/CeO2 catalysts were prepared by an impregnation method, and were tested for CO oxidation. It was found that the activity of Ir/CeO2 catalysts for CO catalytic oxidation rose first and then declined with Ir loading. The catalysts showed the highest activity when Ir content was 1%. Ir existed in the form of IrO2 in the Ir/CeO2 catalysts. IrO2 was highly dispersed with low Ir loading (<= 1%), and existed as crystalline phase with high Ir loading (>1%). Ir particle size increased gradually with Ir loading, but specific rate and turnover frequency (TOE) declined gradually. It indicated that the catalyst with small particle size had a higher CO reactivity. It was also found that for CO oxidation, the activity of Ir catalyst with metal state was higher than that with oxidation state.