Mechanism of Photooxidation of Alcohol over Nb2O5
Mechanism of Photooxidation of Alcohol over Nb2O5
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DOI：
10.1021/jp901603p
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发表时间：
2009-10
影响因子：
3.7
通讯作者：
T. Shishido;Toshiaki Miyatake;K. Teramura;Y. Hitomi;H. Yamashita;Tsunehiro Tanaka
中科院分区：
文献类型：
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作者：
T. Shishido;Toshiaki Miyatake;K. Teramura;Y. Hitomi;H. Yamashita;Tsunehiro Tanaka
在没有有机溶剂的情况下，在氧化铌（Nb2O5）上，在低温下选择性地光氧化醇生成羰基化合物。虽然Nb2O5不能吸收bb0 ~ 390 nm波长的光，但1-戊醇在约480 nm的辐照下仍能进行光氧化。这一观察结果表明，乙醇在Nb2O5上的光活化机制不同于半导体光催化中的经典电子转移机制（在导带形成激发态电子，在价带形成正空穴）。基于FT-IR和ESR测试，提出了以下机理：在黑暗中，乙醇作为醇类物质吸附在Nb2O5上。吸附在Nb2O5上的醇酯通过将一个电子转移到导带将Nb5+还原为Nb4+而被激活，并在醇酯上留下一个空穴。形成的烯基自由基转化为羰基化合物。产物被解吸，然后被还原的Nb4+位点被t…
Photooxidations of alcohols to carbonyl compounds proceed selectively at a low temperature over niobium oxide (Nb2O5) without organic solvents. Although Nb2O5 is not able to absorb light at >390 nm wavelengths, the photooixdation of 1-pentanol proceeded under irradiation up to ca. 480 nm. This observation indicates that the photoactivation mechanism of alcohol over Nb2O5 is different from the classical electron transfer mechanism found in semiconductor photocatalysis (the formation of an excited electron in the conduction band and the positive hole in the valence band). On the basis of FT-IR and ESR measurements, the following mechanism is proposed: Alcohol is adsorbed onto Nb2O5 as an alcoholate species in the dark. Alcoholate adsorbed on Nb2O5 is activated by transferring an electron to the conduction band reducing Nb5+ to Nb4+, and leaving a hole on the alcoholate. The formed alkenyl radical is converted to a carbonyl compound. The product is desorbed and then the reduced Nb4+ sites are reoxidized by t...