Effect of Aldehyde and Carboxyl Functionalities on the Surface Chemistry of Biomass-Derived Molecules

The adsorption and decomposition of acetaldehyde and acetic acid were studied on Rh(100) to gain insight into the interaction of aldehyde and carboxyl groups of biomass-derived molecules with the surface. Temperature programmed reaction spectroscopy (TPRS) was used to monitor gaseous reaction products, whereas Reflection absorption infrared spectroscopy (RAIRS) was used to determine the nature of surface intermediates and reaction paths. The role of adsorbate interactions in oxygenate decomposition chemistry by varying the surface coverage. Acetaldehyde adsorbs in an η2 (C,O)-configuration for all coverages, where the carbonyl group binds to the surface via the C and O atoms. Decomposition occurs below room temperature (180-280 K) via C-H and C-C bond breaking which releases CO, H and CHx species on the surface. At low coverage CHx dehydrogenation dominates and surface carbon is produced alongside H2 and CO. Instead, at high coverage about 60% of the CHx hydrogenates to form methane, whereas only 40% of t...