Adsorption, polymerization and decomposition of acetaldehyde on clean and carbon-covered Rh(111) surfaces

The adsorption and dissociation of acetaldehyde were investigated on clean and carbon-covered Rh(111) single crystal surfaces by electron energy loss spectroscopy (EELS), temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS) and work function (Delta phi) measurements. Acetaldehyde is a starting material for the catalytic production of many important chemicals and investigation of its reactions motivated by environmental purposes too. The adsorption of acetaldehyde on clean Rh(111) surface produced various types of adsorption forms. eta(1)-(O)-CH3CHOa and eta(2)-(O,C)-CH3CHOa are developing and characterized by HREELS. eta(1)-CH3CHOa partly desorbed at T-p = 150 K, another part of these species are incorporated in trimer and linear 2D polimer species. The desorption of timers (at amu 132) were observed in TPD with a peak maximum at; = 225 K. Above this temperature acetaldehyde either desorbed or bonded as a stable surface intermediate (eta(2)-CH3CHOa) on the rhodium surface. The molecules decomposed to adsorbed products, and only hydrogen and carbon monoxide were analyzed in TPD. Surface carbon decreased the uptake of adsorbed acetaldehyde, inhibited the formation of polymers, nevertheless,, it induced the C O bond scission and CO formation with 40-50 K lower temperature after higher acetaldehyde exposure. (C) 2017 Elsevier B.V. All rights reserved.