Abstract
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 irradiation. 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 adatom near the HCHO molecule. Furthermore, single HCHO molecule adsorbed on the bare TiO2(110) 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.
Published Version
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