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

Abstract

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.

CO oxidation on mesoporous SBA-15 supported CuO–CeO2catalyst prepared by a surfactant-assisted impregnation method

“…The weak peak at about 600 cm À1 can be attributed to the presence of oxygen vacancies in the CeO 2 lattice. 26,39,40 The presence of oxygen vacancies on all catalysts is due to the incorporation of Cu 2+ into the CeO 2 lattice, 14 in accordance with the decrease of lattice parameters as shown in Table 1. The ratios of the peak area of oxygen vacancies to that of main peak (A 600 /A 455 ) for these catalysts are presented in Table 2.…”

Solvothermal synthesis in ethylene glycol and catalytic activity for CO oxidation of CuO/CeO2 catalysts

“…The Cu species of samples prepared by deposition-precipitation method are uniformly dispersed, but the preparation process is complex and it is easy for the impurities such as precipitants to get into the catalysts [20]. As a result, various methods have been developed to obtain highly active CuO/CeO 2 catalyst such as template method [21], modified sol-gel method [22], and flame spray pyrolysis [23]. However, these methods generally suffer from some harsh conditions, such as the use of templates [21], and hyperthermal treatment [22,23].…”

Probing Surface Properties and Reaction Intermediates During Heterogeneous Catalytic Oxidation of Acetaldehyde

“…Bare and Cu-loaded CeO 2 , TiO 2 , ZrO 2 , Al 2 O 3 , [11][12][13][14] and SiO 2 catalysts were prepared by one-step flame spray pyrolysis (FSP). [43,44] Metalorganic-based precursors, consisting of 0.5 m cerium 2-ethylhexanoate (Strem, 49 % in 2-ethylhexanoic acid), titanium tetraisopropoxide (Aldrich, 97 % in propanol), zirconium propoxide (Aldrich, 70 % in propanol), aluminum sec-butoxide (Strem, 98 %) or tetraethyl orthosilicate (98 %) and a predetermined amount of Cu 2-ethylhexanoate (Aldrich, > 99.9 %) in xylene (Riedel de Haen, 96 %) were delivered at 5 mL min À1 using a syringe pump (Inotech R232).…”

“…These catalysts were synthesized by one-step flame spray pyrolysis and were thoroughly characterized by us [11,12] as well as by others. [13,14] Previous reports suggest that catalytic ACA oxidation is likely to occur via a succession of adsorption, dissociation and oxidation reactions, [15] however, the energetics, kinetics and active sites for these processes are yet to be established.…”