Temperature-Dependent Reactions of Phthalic Acid on Ag(100)

Abstract

We have investigated the adsorption and temperature-dependent reactions of phthalic acid on Ag(100), in the temperature range 110-700 K, by synchrotron radiation X-ray photoelectron spectrocopy (SR-XPS), temperature-programmed desorption (TPD) and near-edge X-ray absorption fine structure (NEXAFS). Phthalic acid adsorbs intact at 110 K, but decomposes to phthalic anhydride and polyanhdride at 150 K. When heated further, phthalic anhydride desorbs at 250 K, leaving only polyanhydride on the surface, which at 350 K decomposes into a carboxylate, through desorption of phthalic anhydride and water. The carboxylate is stable until 500 K, after which it decomposes, through desorption of CO2 and benzene, into carbon; the latter diffuses into the bulk, leaving only a little carbon on the Ag(100) surface at 600 K.