Different distributions of the active composition Pd and Cu in the systems of Pd (N)–Cu (N)/Al₂O₃ and Pd(C)–Cu(C)/Al₂O₃.

Researchers of the State Key Laboratory for Oxo Synthesis and Selective Oxidation of the Lanzhou Institute of Chemical Physics (LICP) of the CAS have studied the anion ion effects of copper precursor on the catalytic activities of the Pd–Cu catalysts. They synthesized bimetallic Pd–Cu catalysts from different copper precursors and investigated their catalytic properties for CO oxidation.

The characterization results indicate that chloride and sulfate precursors lead to formation of the high dispersed Cu metallic particle, while acetate and nitrate precursors lead to formation of the large aggregated Cu particles. The highly dispersed catalysts exhibit better catalytic activities for CO oxidation. In the Pd–Cu catalyst prepared from chloride and sulfate precursors, the Pd and Cu exist in alloy state and can be reduced easily, which might be the reason for the excellent properties for CO oxidation. The increase of Cu content can promote the catalytic activities of catalyst prepared from nitrate precursor. Pd species dispersed as the Cu-rich alloy on catalysts prepared with nitrate precursor, while the Pd species segregated on catalyst surface prepared with chloride precursor.

Catalytic oxidation of carbon monoxide is an important process for many applications. Although Au or Pt, Ru, Rh or Ir catalysts exhibit good activity for CO oxidation, precious metal loading is still disadvantageous with regards to its high cost. The use of Pd as the only noble component has received considerable attention from point of economical view. Although Pd exhibits remarkable activity in many oxidation reactions, comparatively less publication has been focused on CO oxidation reaction. Moreover, although the modification of Pd phase with addition of Cu, or tuning chemical environment of Cu with the CuCl2–PdCl2 or Cu (NO3)2–Pd (NO3)2 precusors have been extensively studied, the detailed studies focused on effect of anion ions on the dispersion and reducibility of noble metals and their interaction with support are relatively scarce.

The work has received support from the National Program on Key Basic Research Project of China and National High-tech R&D Program of China and Solar Energy Project of Chinese Academy of Sciences.

The detailed report of the work has been published in International Journal of Hydrogen Energy (International Journal of Hydrogen Energy 35(2010)7253-7260).

International Journal of Hydrogen Energy Paper