Adsorption and reactions of dimethyl and diethyl ethers on Mo2C/Mo(1 0 0)

The adsorption, desorption and dissociation of dimethyl ether and diethyl ether on Mo2C/Mo(1 0 0) have been investigated by work function, thermal desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). The adsorption of both molecules at 100 K caused a significant decrease in the work function of the Mo2C/Mo(1 0 0) surface. In the case of dimethyl ether almost 90% of the adsorbed monolayer desorbed intact with a Tp = 286 K. Another part decomposed to CO (Tp = 330 and 960 K) and H2 (Tp = 330 and 400 K). The desorption of diethyl ether at monolayer occurred with Tp = 256 and 340 K. Another fraction underwent decomposition as indicated by the release of CO (Tp = 336 and 436 K) and H2 (Tp = 400 K). In addition, the formation of ethylene (Tp = 342 K) and a very small amount of methane (Tp = 380 K) was also observed. HREEL spectra of both ethers confirmed their molecular adsorption at 100 K. From the spectral changes occurred upon increasing the exposures and in off-specular direction some conclusions were drawn on the bonding of the adsorbed molecules. Analysis of the HREEL spectra of the annealed layers suggested that in the primary steps the adsorbed ethers dissociate to methyl and methoxy (dimethyl ether), and to ethyl and ethoxy (diethyl ether) species, which react further to yield the desorption products.