Chakarova, K.; Drenchev, N.; Mihaylov, M.; Hadjiivanov, K. Interaction of O2 with Reduced Ceria Nanoparticles at 100–400 K: Fast Oxidation of Ce3+ Ions and Dissolved H2. Catalysts2024, 14, 45.
Chakarova, K.; Drenchev, N.; Mihaylov, M.; Hadjiivanov, K. Interaction of O2 with Reduced Ceria Nanoparticles at 100–400 K: Fast Oxidation of Ce3+ Ions and Dissolved H2. Catalysts 2024, 14, 45.
Chakarova, K.; Drenchev, N.; Mihaylov, M.; Hadjiivanov, K. Interaction of O2 with Reduced Ceria Nanoparticles at 100–400 K: Fast Oxidation of Ce3+ Ions and Dissolved H2. Catalysts2024, 14, 45.
Chakarova, K.; Drenchev, N.; Mihaylov, M.; Hadjiivanov, K. Interaction of O2 with Reduced Ceria Nanoparticles at 100–400 K: Fast Oxidation of Ce3+ Ions and Dissolved H2. Catalysts 2024, 14, 45.
Abstract
The interaction between O2 and reduced ceria nanocubes was mainly investigated by FTIR spectroscopy. Nanorods and nanoparticles were also studied for comparison. Adsorption of O2 at 100 K on unreduced ceria produces only O2 molecularly adsorbed on Ce4+ sites. The Ce3+ cations in H2-reduced ceria were monitored by the 2F5/2 → 2F7/2 electronic transition band at 2133-2095 cm-1. This band possesses a fine structure well resolved at 100 K. The positions of the individual components depend on the Ce3+ environment, including the presence of nearby species such as OH groups. Even at 100 K, the interaction of O2 with reduced ceria leads to fast oxidation of about half of the Ce3+ cations, including all Ce3+ sites bound to OH groups and carbonates, and the simultaneous formation of superoxo (O2) and peroxo (O22) species. The remaining fraction of Ce3+ sites disappears upon heating up to 348 K. At higher temperatures, the peroxo species decompose directly, yielding lattice oxygen. Superoxides are converted to hydroperoxides, which then decompose to terminal OH groups. Reduced samples evacuated at T < 773 K contain sorbed H2. Part of this hydrogen is also fast oxidized to H2O even at 100 K.
Chemistry and Materials Science, Surfaces, Coatings and Films
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