Flame‐Synthesized Ceria‐Supported Copper Dimers for Preferential Oxidation of CO

• Published in: Advanced functional materials 2009-02, Vol.19 (3), p.369-377
• Main Authors: Kydd, Richard, Teoh, Wey Yang, Wong, Kenneth, Wang, Yong, Scott, Jason, Zeng, Qing‐Hua, Yu, Ai‐Bing, Zou, Jin, Amal, Rose
• Format: Article
• Language: English
• Subjects: ceria; copper; dimerization; flame spray pyrolysis; nanoparticles; structure–property relationship
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200801211

Rapid synthesis of CuCeO2 catalysts by flame spray pyrolysis produces highly active Cu dimer morphologies without the need for additional catalyst pretreatment. The active Cu component is enriched onto the CeO2 surface at concentrations higher than the nominal loading with no evidence of amorphous or crystalline CuO phase. Increasing the Cu content results in a morphological transition from isolated Cu monomers to oxygen‐bridged dimers and an associated increase in oxygen vacancy concentration. Dimer‐containing CuCeO2 catalysts display high levels of activity and selectivity in the low‐temperature preferential oxidation of CO. Experimental measurements and simulations suggest that the geometry of the dimer presents a comparatively ionic CuO bond at the catalyst surface. Further studies indicate that these ionic dimer species promote preferential CO oxidation at lower temperatures than observed for monomeric Cu species. This is the first report to explicitly propose and demonstrate that the structural distortion associated with the formation of Cu dimers directly induces increased bond ionicity at the catalyst surface and that these changes are responsible for improved catalytic activity. Flame spray pyrolysis (FSP) produces highly dispersed Cu–CeO2 catalysts. Transformation of the Cu species from monomer to dimer takes place as Cu content increases. As‐prepared catalysts display high and stable activity for the preferential oxidation of CO (PROX). This work demonstrates how structural and electronic changes lead to heightened levels of reducibility and catalytic activity and shows that FSP is an effective and simple strategy for producing highly active PROX catalysts.