A Novel Post‐Synthesis Modification of CuO‐CeO₂ Catalysts: Effect on Their Activity for Selective CO Oxidation

Abstract

Copper oxide nanoparticles were dispersed onto the surface of ceria nanorods, while a post‐synthesis modification was applied to the reference sample using ammonia solutions. The modified catalysts were characterized with a variety of analytical techniques, providing useful information on the effect of the Cu:NH3 ratio, employed in the modification step, on the physicochemical properties. Re‐dispersion of the active copper species under extremely basic conditions promoted the reducibility and the oxygen mobility of the catalyst, thus resulting in a more active and selective catalyst for preferential CO oxidation.

The Influence of Preparation Method on the Physicochemical Characteristics and Catalytic Activity of Co/TiO2 Catalysts

“…The first peak is assigned to Co-O-Ti, while the second peak is due to Co-O-Co polymerization in accordance with previous works for Co deposition on an Al2O3 surface [21,24]. Generally, this peak has been observed in many cases where a transition metal ion (either as oxyanion, MO x z-, or hydrated cation, M(H 2 O) x z+ ) deposited on the TiO 2 surface and was attributed to the charge transfer between Ti-O-M bonds [18][19][20]22,23]. The intensity of the peaks denotes that the interactions were higher in the case of the EDF sample, while the shift observed in lower energy supports this finding.…”

Influence of the Hydrothermal Parameters on the Physicochemical Characteristics of Cu−Ce Oxide Nanostructures

“…[49,55] The O 1s spectra is illustrated in Figure 4b. [35,45,75] In our case, the lower binding energy of Cu 2p 3/2 confirms the presence of Cu + species over the CuCeO x catalysts. The other peaks at 530.0-530.7 eV (O'') are assigned to the absorbed oxygen or oxygen in hydroxyl groups.…”

“…[71,73,74] According to the literature, the binding energy of Cu 2p 3/2 ranges at 943-935 eV, while the lower binding energy indicates the presence of Cu + species. [35,45,75] In our case, the lower binding energy of Cu 2p 3/2 confirms the presence of Cu + species over the CuCeO x catalysts. This can be due to the strong interaction of copper clusters with ceria and the substitutions at the interface of two oxides because of the similar ionic radius of Ce 4 + and Cu + ions.…”

“…[10][11][12][13] An ideal catalyst for CO-PROX reaction should be highly active and selective in order to avoid the undesired parallel H 2 oxidation in a wide temperature range, tolerant to CO 2 and H 2 O present at the reformate stream, and stable for a long time. [33][34][35] The enhanced catalytic performance of CuÀ Ce oxide catalysts can be attributed to a synergistic effect between copper oxide and ceria, since the copper oxide-ceria interfacial sites are mainly related with CO oxidation activity. However, the application of the above catalytic systems is prohibited by low selectivity for the desired reaction (i. e. CO oxidation), poor resistance towards the presence of CO 2 and H 2 O in the reaction mixture and dramatically high cost of precious metals.…”

“…[28][29][30][31][32] More specifically, CuÀ Ce oxide catalysts are more active and selective than the noble metal-based catalysts, while they are less active but more selective and more stable as compared to gold-based catalysts. [33][34][35] The enhanced catalytic performance of CuÀ Ce oxide catalysts can be attributed to a synergistic effect between copper oxide and ceria, since the copper oxide-ceria interfacial sites are mainly related with CO oxidation activity. [36][37][38][39] In addition, the activity of this class of materials depends on welldispersed copper oxide entities and their strong interaction with CeO 2 support, the facile interplay between Cu 2 + /Cu + and Ce 3 + /Ce 4 + , the generation of abundant oxygen vacancies and the highest concentration of active lattice oxygen.…”