Mechanism of ozone decomposition on a manganese oxide catalyst. I. In situ Raman spectroscopy and ab initio molecular orbital calculations
Mechanism of ozone decomposition on a manganese oxide catalyst. I. In situ Raman spectroscopy and ab initio molecular orbital calculations
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DOI：
10.1021/ja981441
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发表时间：
1998-09-09
影响因子：
15
通讯作者：
Oyama, ST
中科院分区：
文献类型：
--
作者：
Li, W;Gibbs, GV;Oyama, ST
采用拉曼光谱法对负载型氧化锰催化剂在反应条件下的臭氧分解进行了研究。通过原位拉曼光谱和O-18同位素取代测量，在884 cm（-1）处观察到一种具有拉曼信号的吸附物质，并将其鉴定为过氧化氢物质。观察到该吸附物质的同位素位移nu(O-18)/nu（O-16）值为0.946，与用谐振子模型计算的过氧化氢物质的比值0.943非常吻合。用Mn(OH)(4)(O-2)（+）作为吸附物种的模型化合物，从头算分子轨道计算证实了这一指派。通过精心设计的实验，包括同位素取代，阐明了臭氧分解的反应机理。反应顺序包括臭氧解离吸附形成氧分子和氧原子，氧原子与气态臭氧反应形成吸附的过氧化物和气相氧，以及过氧化物中间体的分解和分子氧的解吸。
Ozone decomposition was investigated under reaction conditions by using Raman Spectroscopy on a supported manganese oxide catalyst. An adsorbed species with a Raman signal at 884 cm(-1) was observed during reaction, and was identified as a:peroxide species by a combination Of in situ Raman spectroscopy and O-18 isotopic substitution measurements. The observed isotope shift nu(O-18)/nu(O-16) value of this adsorbed species was 0.946, in excellent agreement with the ratio calculated for a peroxide species (0.943) by using a harmonic oscillator model. Ab initio molecular orbital calculations confirmed this assignment, using Mn(OH)(4)(O-2)(+) as a model compound for the adsorbed species. The reaction mechanism of ozone decomposition was elucidated with carefully designed experiments, including isotopic substitution. The reaction sequence involved dissociative adsorption of ozone to form an oxygen molecule and an atomic oxygen species, reaction of the atomic species with gaseous ozone to form an adsorbed peroxide species and gas-phase oxygen, and decomposition of the peroxide intermediate and desorption of molecular oxygen.