Abstract
Under ambient conditions, almost all metals are coated by an oxide. These coatings, the result of a chemical reaction, are not passive. Many of them bind, activate and modify adsorbed molecules, processes that are exploited, for example, in heterogeneous catalysis and photochemistry. Here we report an effect of general importance that governs the bonding, structure formation and dissociation of molecules on oxidic substrates. For a specific example, methanol adsorbed on the rutile TiO2(110) single crystal surface, we demonstrate by using a combination of experimental and theoretical techniques that strongly bonding adsorbates can lift surface relaxations beyond their adsorption site, which leads to a significant substrate-mediated interaction between adsorbates. The result is a complex superstructure consisting of pairs of methanol molecules and unoccupied adsorption sites. Infrared spectroscopy reveals that the paired methanol molecules remain intact and do not deprotonate on the defect-free terraces of the rutile TiO2(110) surface.
Highlights
IntroductionAlmost all metals are coated by an oxide. These coatings, the result of a chemical reaction, are not passive
Under ambient conditions, almost all metals are coated by an oxide
Using density-functional theory (DFT) calculations, we show that strongly interacting adsorbates can locally lift the relaxation present on the pristine surface beyond their immediate adsorption site
Summary
Almost all metals are coated by an oxide. These coatings, the result of a chemical reaction, are not passive. Among the many different oxides of technological relevance, titania takes a special role since presently the [110] surface of rutile, the most common modification of titania, is generally considered to be the oxide substrate which is understood best, both experimentally and theoretically1 Despite this progress, the available experimental information on how molecules bind to this important surface is incomplete and discussed controversially, even for small adsorbates like water, and simple alcohols like methanol. Using density-functional theory (DFT) calculations, we show that strongly interacting adsorbates can locally lift the relaxation present on the pristine surface beyond their immediate adsorption site This adsorbate-induced substrate relaxation leads to a substantial reduction of binding energies for further molecules. The second method is infrared (IR) reflection-absorption spectroscopy (IRRAS), which is applied to this adsorbate system for the first time, to the best of our knowledge
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
