Exchange between Physisorbed and Chemisorbed Formic Acid on Titania.

NMR spin labelling and isotopic labelling have been used to characterize exchange between physisorbed and chemisorbed formic acid and within chemisorbed formic acid adsorbed on Ti0(2). Contrary to behavior assumed in earlier studies, the exchange between physisorbed and chemisorbed formic acid has a relatively slow time constant between 2 and 400 s at 298K. Reorientation occurs within the chemisorbed adlayer with a broad distribution of time constants centered at ~ 20 ms. The application of NMR spin-labelling to characterization dynamics at interfaces is discussed.