The Impact of Ceria Loading on the CuOx−CeO2 Interaction and Performance of AuCu/CeO2−SiO2 Catalysts in CO‐PROX Reaction

• Published in: European journal of inorganic chemistry 2021-10, Vol.2021 (40), p.4222-4229
• Main Authors: Rodrigues Fiuza, Tanna Elyn, Santos Gonçalves, Danielle, Zanchet, Daniela
• Format: Article
• Language: English
• Subjects: Atom Mobility; Bimetals; Carbon monoxide; Catalysts; Catalytic activity; Ceria; Cerium oxides; CO-PROX; Copper; Crystal lattices; Gold; Inorganic chemistry; Intermetallic compounds; Nanoparticles; Oxidation; Silicon dioxide; Stabilization
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202100561

The use of CeO2 as a promoter for non‐reducible supports, such as SiO2, enhances the catalytic activity by facilitating the activation of species such as O2 and H2O. However, in the case of the bimetallic nanoparticles (NPs), the presence of promoters may also influence the migration of the metallic species, dramatically impacting the stabilization of catalytic sites and as consequence, the overall catalytic performance. In the case of AuCu alloy supported catalysts, the reduced form, i. e., AuCu alloy, or the oxidized form, i. e., Au−CuOx species, present different activities/selectivities. Moreover, several parameters, such as reactional conditions, AuCu particle size, support nature, and pretreatments dictate which species are stabilized on the catalyst surface. The preferential oxidation of CO (CO‐PROX) reaction, that takes place under the H2‐rich stream, favors the stabilization of the reduced form of the AuCu catalysts. However, the Cu distribution in the crystal lattice and the final composition of the AuCu NPs are dependent on the mobility of the Cu species on the support. In this work, we show that the loading of the CeO2 as a promotor in AuCu/SiO2 catalysts impacts the CeOx species and the Cu reincorporation into the Au lattice and consequently, the activity and stability of the catalysts under CO‐PROX reaction. By ex situ and in situ techniques we found a direct relation between the Ce3+ fraction (related to highly dispersed species) in the support with the lower Cu reincorporation in the Au1–xCux alloy after reduction. The catalyst with the lower CeO2 loading presented the higher CO2 production rate, but faster deactivation. The higher Cu reincorporation was related to the higher stability under preferential oxidation of CO (CO‐PROX) reaction.