Abstract
The adsorption and reaction of formaldehyde (CH2O) on the oxidized rutile TiO2(110) surface were studied by temperature-programmed desorption (TPD), scanning tunneling microscopy (STM), infrared reflection–absorption spectroscopy (IRRAS), and density functional theory (DFT) calculations. The experimental and theoretical data reveal the presence of various species depending on the temperature and coverage. Exposure to formaldehyde at 65 K leads to the formation of CH2O multilayers, which desorb completely upon heating to 120 K. After smaller exposures at low temperatures (45–65 K), STM allowed us to identify individual, isolated CH2O monomers. The theoretical results indicate that these monomers are bound to the surface Ti5c sites via σ-donation and adopt a tilted geometry. Upon heating, the CH2O monomers polymerize to form paraformaldehyde (polyoxymethylene, POM) chains, oriented primarily along the Ti5c rows ([001] direction). Upon further heating, POM is found to decompose around 250 K, releasing CH2O i...
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