The adsorption and photochemistry of phenol on Ag(1 1 1)

The adsorption and photochemistry of phenol on Ag(1 1 1) was investigated by temperature programmed desorption (TPD). Three distinct adsorption states were identified, each involving a weakly chemisorbed monolayer, a multilayer, and an intermediate layer in between. The activation energy of desorption was 15.5 kcal/mol for the chemisorbed monolayer, and 16.9 kcal/mol for the multilayer. The sticking probability was highest for the multilayer. Upon irradiation of ultraviolet (UV) light, new peaks were observed in the TPD spectra, suggesting formation of photoproducts. Only the chemisorbed monolayer in direct contact with the metal surface was affected by the UV irradiation. It was proposed that photoinduced generation of energetic electrons lead to the charge transfer photodissociation of the O–H bond of phenol, and the resulting surface phenoxide undergoes recombinative desorption at elevated temperatures.