ChemCatChem - Dec. 2020

Towards the Effect of Pt0/Ptδ+ and Ce3+ Species at the Surface of CeO2 Crystals: Understanding the Nature of the Interactions under CO Oxidation Conditions

Dr. Laís Reis Borges, Dr. Anderson Gabriel Marques da Silva, Dr. Adriano Henrique Braga, Dr. Liane Marcia Rossi, Dr. Marco Aurélio Suller Garcia, Dr. Pedro Vidinha


https://doi.org/10.1002/cctc.202001621





Abstract

We synthesized CeO2 nanowires and nanocubes showing {110}+{100} and {100} surfaces predominantly, respectively, once the different surface energies play a crucial role in the behavior of Ce4+/Ce3+ reversibility. We found out that Pt/CeO2 nanowires presented more Ce3+ content, oxygen vacancies, and atomically dispersed Pt, indicating a stronger Pt−Ce interaction. In contrast, the Pt/CeO2 nanocubes presented a higher contribution of Ptδ+ species, suggesting a well‐controlled Pt particle size (∼1 nm) and significant interaction with ceria, with oxygen species more available at the surface. Thus, we suggest that the ceria‘s different surface energies may lead to different Pt distributions of species over the supports. H2‐reduction treatment led to changes in Pt structure that showed a better catalysis performance for the Pt/CeO2 nanowires essentially, supported by XPS and CO‐DRIFTS. Nevertheless, this step did not cause improved activity to the point of overcoming the nanocubes‐based catalyst, and the reasons were fully discussed. Herein, we propose that catalysts′ performance depends on a complex combination of several materials′ characteristics. These features may lead to different reaction pathways depending on the pre‐treatment of the samples.



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