Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
Phys Chem Chem Phys. 2012 Mar 28;14(12):4188-95. doi: 10.1039/c2cp24036j. Epub 2012 Feb 21.
Gas phase catalytic reactions involving the reduction of N(2)O and oxidation of CO were observed at the molecular level on isolated neutral rhodium clusters, Rh(n) (n = 10-28), using mass spectrometry. Sequential oxygen transfer reactions, Rh(n)O(m-1) + N(2)O → Rh(n)O(m) + N(2) (m = 1, 2, 3,…), were monitored and the rate constant for each reaction step was determined as a function of the cluster size. Oxygen extraction reactions by a CO molecule, Rh(n)O(m) + CO → Rh(n)O(m-1) + CO(2) (m = 1, 2, 3,…), were also observed when a small amount of CO was mixed with the reactant N(2)O gas. The rate constants of the oxygen extraction reactions by CO for m ≥ 4 were found to be two or three orders of magnitude higher than the rate constants for m ≤ 3, which indicates that the catalytic reaction proceeds more efficiently when the reaction cycles turn over around Rh(n)O(m) (m ≥ 4) than around bare Rh(n). Rhodium clusters operate as more efficient catalysts when they are oxidized than non- or less-oxidized rhodium clusters, which is consistent with theoretical and experimental studies on the catalytic CO oxidation reaction on a rhodium surface.
使用质谱法在孤立的中性铑簇 Rh(n)（n = 10-28）上观察到涉及 N(2)O 还原和 CO 氧化的气相催化反应。监测了顺序氧转移反应，Rh(n)O(m-1) + N(2)O → Rh(n)O(m) + N(2)（m = 1, 2, 3，...），并确定了每个反应步骤的速率常数作为簇大小的函数。当少量 CO 与反应物 N(2)O 气体混合时，也观察到 CO 通过 Rh(n)O(m)（m = 1, 2, 3，...）的氧提取反应，对于 m ≥ 4 的氧提取反应的速率常数比 m ≤ 3 的速率常数高两个或三个数量级，这表明当反应循环在 Rh(n)O(m)（m ≥ 4）周围而不是在裸露的 Rh(n)周围进行时，催化反应更有效。氧化态的铑簇比非氧化态或较少氧化态的铑簇作为更有效的催化剂发挥作用，这与在铑表面上进行的催化 CO 氧化反应的理论和实验研究一致。
