Reduction Site in Ce n V m O k + Revealed by Gas Phase Thermal Desorption Spectrometry
Vanadia supported on ceria shows particularly high catalytic reactivity. To elucidate its reduction site, cationic cerium-vanadium oxide clusters, Ce n V m O x + (n = 1–6, m = 0–5), were generated in the gas phase and their thermal response, such as reduction by oxygen release, was investigated by gas phase thermal desorption spectrometry. Stoichiometric and near-stoichiometric Ce n V m O x + clusters were dominantly formed, suggesting that Ce and V atoms in thermally stable clusters at 310 K have the oxidation states of + 4 and + 5, respectively. An oxygen molecule O2 was found to desorb from the clusters, resulting in formation of Ce n V m O x−2 +, upon heating. Presence of more than two Ce atoms in the clusters for odd values of m, or more than three Ce atoms for even values of m lowered the desorption temperature, indicating that not V atoms (+ 5 to + 4) but Ce atoms (+ 4 to + 3) in Ce n V m O x + tend to be reduced.
KeywordsCluster Reduction Thermal desorption spectrometry Metal oxide Oxidation state
This work was supported by Grant-in-Aid for Challenging Exploratory Research (No. 26620002), for Young Scientists (B) (No. 17K14433), and for JSPS Fellows (No. 17J02017) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT). The computations were partially performed using Research Center for Computational Science in Okazaki, Japan. T.N. is grateful for a JSPS Research Fellowship. The authors thank Dr. Ryuzo Nakanishi, Dr. Satoshi Takahashi and Dr. Ken Miyajima for helpful discussion.
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