Adsorption and dissociation of dimethyl ether on clean and oxygen-dosed Rh(111)

The interaction of dimethyl ether (DME) with clean and oxygen-covered Rh(111) surfaces has been investigated by TDS and HREELS. The adsorption of DME on the clean Rh(111) surface was reversible at 100 K; all the adsorbed DME was released to the gas phase after annealing without any sign of decomposition. On increasing the adsorption temperature to 250-300 K, the appearance of an intense HREELS feature at 1230 cm(-1) indicated that a reaction channel opened up for the thermally activated decomposition of DME. The reaction intermediate of this process was tentatively identified as CHO or CHxOCHx(a) species, the decomposition of which resulted in adsorbed CO and hydrogen. On the O-precovered Rh(111) surface, a fraction of DME was stabilised in a state characterized by T-p = 245 K. On the other hand, the interaction of DME with adsorbed O led to the formation of CH3O(a) species at 100-195 K. Above 250 K, this species is decomposed and oxidized, leading to the evolution of H2O and CO2. (C) 1997 Elsevier Science B.V.