(558f) Superior Active Oxygen Transfer Ability of CuO/CeO2 catalyst with Enhanced Activity for Preferential CO Oxidation

Superior Active
Oxygen Transfer Ability of CuO/CeO₂ Catalyst with Enhanced Activity
for Preferential CO Oxidation

Yang Xia, Jiazheng Lao,
Dang-guo Cheng,* Fengqiu Chen and Xiaoli Zhan

College of
Chemical and Biological Engineering, Zhejiang University,
38 Zheda Road, Hangzhou 310027, China

Abstract: Preferential
CO oxidation (PROX) in a H₂-rich gas stream is commonly accepted to
remove CO to a trace level below 10 ppm. CuO/CeO₂ is one of the efficient
catalysts for this reaction since the peculiar synergistic properties caused by
the metal - support interaction. In this work, the two-electron defects amount
on CeO₂ surface is found to be crucial for such interaction, it can
be modulated and greatly enriched using ultrasound-assisted co-precipitation
method. Thus, by controlling ultrasound time (0, 5, 15, 30, 35, 45, and 60 min),
a series of CuO/CeO₂ catalysts with different interaction (CuO/CeO₂-US0,
CuO/CeO₂-US5, CuO/CeO₂-US15,
CuO/CeO₂-US30, CuO/CeO₂-US35, CuO/CeO₂-US45,
and CuO/CeO₂-US60) is formed and the sample
with the strongest interaction (CuO/CeO₂-US35) had a striking
improvement in activity, as showed in Fig. 1a. We explored the structure
using characterization techniques and DFT calculation. It clearly shows that Cu
ions incorporate into the two-electron defects site and compensate the charge
discrepancy (simultaneously generate Cu⁺ and Ce³⁺),
forming the Cu-O-Ce structure. Electronic redistribution is then related to
this structure, resulting in unsaturated CuO species which has strong
interaction with CeO₂. And the catalyst with a
stronger interaction has more unsaturated CuO species with less coordinated
oxygen number, this induces
better spillover of active oxygen. In Fig. 1b, a direct relationship between active oxygen
replenishment and TOF can be seen. During the reaction, the improvement of active oxygen transfer
though redox cycle is identified to be crucial for activity enhancement. The schematic
illustration was showed in Fig. 1c.

Fig.1 (a) Conversion of CO as a function
of temperature for PROX, (b) O₂
replenishment of CuO/CeO₂ as a function of TOF₁ at 60 ¡ãC, (c) Schematic illustration
of CO oxidation mechanism on CuO/CeO₂ with strong interaction.

* Corresponding author. Tel.: +86 571 87953382; Fax: +86
571 87951227

E-mail address: dgcheng@zju.edu.cn (D.G.
Cheng) fqchen@zju.edu.cn (F.Q. Chen)

             
xlzhan@zju.edu.cn (X.L. Zhan)
yangxia.koo@qq.com (Y. Xia)