Doping effect of precious metal on the activity of CuO-CeO₂ catalyst for selective oxidation of CO

Precious metals (Pt, Pd and Ru)-doped copper oxide-ceria (CuO-CeO₂) catalysts were prepared by a combination of conventional co-precipitation and impregnation methods and evaluated for the selective oxidation of carbon monoxide in a hydrogen-rich gas stream. It was found that the doping with the precious metal did not change the crystal structure of the catalyst. The binding energy of copper in the precious metal-doped CuO-CeO₂ catalyst shifted to a higher value. This indicates that a part of the copper in the CuO-CeO₂ catalyst is phase-separated and there is some possibility of the formation of copper chloride on the surface of the catalyst. The added precious metal inhibited the phase separation of copper. The degree of phase separation depended on the type of precious metal and the amount of precious metal loading. The catalytic activity for selective oxidation of carbon monoxide (CO) was the highest in the case of Pt-doped catalyst due to the strong interaction between doped Pt and CuO-CeO₂ catalyst. However, the activity of Pd- or Ru-doped catalyst for selective oxidation of CO was much less because doped Pd and Ru have good activity for hydrogen oxidation.