Dai Wenxin, Chen Xun, Wang Xuxu, Liu Ping, Li Danzhen, Li Guanshe, Fu Xianzhi
Research Institute of Photocatalysis, State Key Laboratory Breeding Base of Photocatalysis, Fuzhou University, Fuzhou, 350002, China.
Phys Chem Chem Phys. 2008 Jun 14;10(22):3256-62. doi: 10.1039/b718541c. Epub 2008 Mar 20.
The catalytic oxidation of CO was performed over Au/TiO(2) under UV irradiation in the presence of H(2) in different reaction systems. It was found that the introduction of H(2) enhanced the CO thermocatalytic oxidation in a CO pre-introduced system (CO/O(2)vs. CO/H(2)/O(2)), but suppressed that in an O(2) pre-introduced (O(2)/CO vs. O(2)/H(2)/CO) system. Although the CO oxidation in both CO/H(2)/O(2) and O(2)/H(2)/CO systems could be remarkably enhanced under UV irradiation, the oxidation of H(2) was suppressed under UV irradiation. It was proposed that the dissociative chemisorption H ([triple bond]Ti-H) at surface oxygen vacancy sites of TiO(2) could act as both the electron-acceptors for the photogeneration electrons and the electron-donors for the chemisorbed O(2) at TiO(2), and thus enhance the CO oxidation during the coinstantaneous process of thermocatalysis and photocatalysis. The suppression of H(2) thermocatalytic oxidation under UV irradiation might be ascribed to the electron transfer effect, i.e., the dissociative chemisorption H on Au (Au-H) could be desorbed at the H(2) molecule via accepting the photogenerated electrons from TiO(2).
在不同反应体系中，于紫外线照射及氢气存在的条件下，在Au/TiO₂上进行了一氧化碳的催化氧化反应。研究发现，在预先引入一氧化碳的体系（CO/O₂与CO/H₂/O₂对比）中，氢气的引入增强了一氧化碳的热催化氧化，但在预先引入氧气的体系（O₂/CO与O₂/H₂/CO对比）中却抑制了该氧化反应。尽管在紫外线照射下，CO/H₂/O₂和O₂/H₂/CO体系中的一氧化碳氧化反应均可显著增强，但氢气的氧化在紫外线照射下受到抑制。研究表明，TiO₂表面氧空位处的解离化学吸附氢（[三键]Ti-H）既可以作为光生电子的电子受体，又可以作为TiO₂上化学吸附氧的电子供体，从而在热催化和光催化的同时过程中增强一氧化碳的氧化。紫外线照射下氢气热催化氧化受到抑制可能归因于电子转移效应，即Au上的解离化学吸附氢（Au-H）可通过接受来自TiO₂的光生电子在氢气分子处解吸。
