Photocatalysis offers a new approach for polyol conversion to value-added products. However, the lack of a comprehensive mechanistic understanding limits or even misleads the development of highly selective and efficient photocatalysts for this process. The photochemistry of ethylene glycol (EG) on a reduced rutile-TiO₂(110) surface has been studied using the temperature-programmed desorption (TPD) method. The thermal chemistry of EG on the surface produces ethylene (C₂H₄) and acetaldehyde (CH₃CHO) at high temperature (>500 K); however, in the photoreaction process, formaldehyde (CH₂O) and CH₃CHO products are identified at low temperature (<300 K). The C–C bond cleavage channel to produce CH₂O on the five-coordinated Ti⁴⁺ sites (Ti_5c) and H atoms on the bridging oxygen sites (H_b) dominates at very low EG coverage. The C–O bond cleavage channel to produce CH₃CHO and water on the Ti_5c sites dominates at high EG coverage, which may be affected by the HO_bs and steric hindrance of EG at high EG coverage. The results further demonstrate that photocatalysis may alter the reaction channels of EG decomposition significantly, making it possible for selective photocatalytic polyol conversion in the future.

中文翻译：

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金红石型TiO ₂（110）上与覆盖率有关的乙二醇光化学

光催化为将多元醇转化为增值产品提供了一种新方法。然而，缺乏全面的机理理解限制或什至误导了用于该过程的高度选择性和高效的光催化剂的开发。已使用程序升温脱附（TPD）方法研究了还原的金红石型TiO ₂（110）表面上的乙二醇（EG）的光化学。EG在表面的热化学作用在高温（> 500 K）下产生乙烯（C ₂ H ₄）和乙醛（CH ₃ CHO）；但是，在光反应过程中，甲醛（CH ₂ O）和CH ₃在低温（<300 K）下鉴定出CHO产品。在非常低的EG覆盖率下，CC键断裂通道在五个配位的Ti ⁴⁺位点（Ti _5c）上生成CH ₂ O ，在桥接氧位点（H _b）上生成H原子。在高EG覆盖率下，在Ti _5c位点产生CH ₃ CHO和水的C–O键裂解通道占主导地位，这可能受到高EG覆盖率下EG的HO _b s和空间位阻的影响。结果进一步表明，光催化可以显着改变EG分解的反应通道，从而有可能在将来进行选择性的光催化多元醇转化。