表面羟基辅助甲醛分子在金红石型TiO2（110）表面迁移动力学研究

Diffusion of Formaldehyde on Rutile TIO2（110） Assisted by Surface Hydroxyl Groups

甲醛分子作为甲醇分子的重要光解离产物，其迁移和脱附作用在光催化反应过程中是至关重要的．结合扫描隧道显微镜技术和理论计算发现，由甲醇光解离直接得到的甲醛分子会吸附在两个桥氧羟基之间，并且光照后会有一部分甲醛分子发生迁移和脱附作用．随着甲醛分子周围桥氧羟基数目的减少，其发生光致迁移和脱附的比例也随之降低．当吸附在金红石型TiO2（110）表面的甲醛分子周围没有桥氧羟基存在时，它表现出了非常好的稳定性．结合理论计算表明，桥氧羟基的存在对甲醛分子的迁移和脱附起到了辅助效果．

As the photo-dissociation product of methanol on the TIO2（110） surface, the diffusion and desorption processes of formaldehyde （HCHO） were investigated by using scanning tunneling microscope （STM） and density functional theory （DFT）. The molecular-level images revealed the HCHO molecules could diffuse and desorb on the surface at 80 K under UV laser irra- diation. The diffusion was found to be mediated by hydrogen adatoms nearby, which were produced from photodissociation of methanol. Diffusion of HCHO was significantly decreased when there was only one H alatom near the HCHO molecule. Furthermore, single HCHO molecule adsorbed on the bare Ti02（l10） surface was quite stable, little photo-desorption was observed during laser irradiation. The mechanism of hydroxyl groups assisted diffusion of formaldehyde was also investigated using theoretical calculations.