n V m O k + Revealed by Gas Phase Thermal Desorption Spectrometry]]>

摘要

Abstract 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 O~(2)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.