中文摘要：

采用密度泛函理论方法在M06-2X/6-311G＊水平上模拟了不同反应条件下,Ti O2对苯甲醛的光催化还原和氧化的反应.计算结果表明,苯甲醛的光催化还原和氧化反应均可在常温下发生;在缺氧但有乙醇存在的条件下,乙醇分子可与氧化性物质发生反应,生成醇自由基,苯甲醛主要发生光催化还原反应生成苯甲醇;在有氧气但无乙醇存在条件下,还原性的光生电子被氧气捕获,避免了苯甲醛被还原,主要发生光催化氧化反应生成苯甲酸.

英文摘要：

The photoelectron and photohole could be generated on the surface of TiO2 under the UV irradiation. Some reactive species could be produced indirectly. The photoelectron could be trapped by oxygen leading to yield the superoxide anion radicals, while the photohole can react with the solvent molecules to generate the hydroxyl radical and alcohol radical. The substrate may be reduced by the photoelectron directly, or by alcohol radicals. And it may be oxidized by the photohole directly, or by the reactive species of hydroxyl radicals and superoxide anion radicals. The M06-2X/6-311G＊ method was employed to investigate the selective redox mechanism of benzaldehyde in solution, which was reduced or oxidized by the reactive species generated during the photo-catalyzed process in different reaction conditions. According to the computation results, the photo-redox reaction of benzaldehyde would be happened in room temperature. In oxygen-free ethanol solvent, the ethanol molecules could react with the oxidizing species to yield the alcohol radicals, while benzaldehyde could be mainly reduced to benzyl alcohol. In oxygen-rich without ethanol condition, the reductive photoelectron is trapped by oxygen to prohibit the reduction of benzaldehyde, so benzaldehyde is mainly oxidized to benzoic acid.