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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Identification of a Surface Alkylperoxy Radical in the Photocatalytic Oxidation of Acetone/ O_2 over TiO_2
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Identification of a Surface Alkylperoxy Radical in the Photocatalytic Oxidation of Acetone/ O_2 over TiO_2

机译：TiO_2上丙酮/ O_2光催化氧化中表面烷基过氧自由基的鉴定。

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摘要

The interaction of a coadsorbed mixture of acetone and oxygen with a clean oxidized polycrystalline sample of TiO_2 (P25) was investigated using electron paramagnetic resonance (EPR) spectroscopy. UV illumination of the sample at low temperature (100 K) generated an unstable radical intermediate at the dehydrated (and hydrated) TiO_2 surface. The radical decayed irreversibly at temperatures greater than 150 K but was regenerated by subsequent irradiation at low temperatures. Using a series of isotopically labeled gases (CH_3COCH_3, CD_3-COCD_3, ~(16)O_2, and ~(17)O_2) to aid in the interpretation of the EPR spectrum, the radical was identified as an alkylperoxy species RCH_2OO~· with the spin Hamiltonian parameters of g_1 = 2.0345, g_2 = 2.0070, g_3 = 2.0010, ~HA_1 = 0.34 mT, ~HA_2 = 0.10 mT, ~HA_3 = 0.29 mT, ~(17O)A_(||)(i) = 9.45 mT (for RO~(17)~·), and ~(17O)A_(||) (ii) = 5.52 mT (for R~(17)OO~·). By consideration of the different mechanistic pathways involved in the oxidation of acetone, it was concluded that the observed radical is generated initially by hole transfer to the adsorbed acetone and the identity of the unstable peroxy intermediate must be CH_3COCH_2OO~·.
机译：使用电子顺磁共振（EPR）光谱研究了丙酮和氧气的共吸附混合物与纯净氧化的TiO_2多晶样品（P25）的相互作用。样品在低温（100 K）下的紫外线照射在脱水（和水合）的TiO_2表面产生了不稳定的自由基中间体。自由基在大于150 K的温度下不可逆地分解，但随后在低温下辐照则得以再生。使用一系列同位素标记的气体（CH_3COCH_3，CD_3-COCD_3，〜（16）O_2和〜（17）O_2）来帮助解释EPR光谱，该基团被鉴定为烷基过氧物种RCH_2OO〜·自旋哈密顿参数g_1 = 2.0345，g_2 = 2.0070，g_3 = 2.0010，〜HA_1 = 0.34 mT，〜HA_2 = 0.10 mT，〜HA_3 = 0.29 mT，〜（17O）A_（||）（i）= 9.45 mT（对于RO〜（17）〜·），〜（17O）A_（||）（ii）= 5.52 mT（对于R〜（17）OO〜·）。考虑到丙酮氧化所涉及的不同机理，得出的结论是，观察到的自由基最初是通过空穴转移到吸附的丙酮中而产生的，不稳定的过氧中间体的身份必须是CH_3COCH_2OO〜·。

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