Effects of potassium on the adsorption and dissociation pathways of methanol and ethanol on Mo 2C/Mo(1 0 0)

Abstract

The adsorption, desorption and dissociation of methanol and ethanol on K-dosed Mo 2C/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 Mo 2C/Mo(1 0 0) surface suggesting an electron donation from the O lone pair to carbide surface. Potassium additive stabilized the adsorbed alcohols, and converted a fraction of them to an irreversibly bonded surface species, which decomposed only at higher temperatures, 450–500 K, to yield H 2, CO and CH 4(CH 3OH) and H 2, CO, acetaldehyde and ethylene (C 2H 5OH). From the coincident desorption of major products, H 2, CO and K, we inferred the existence of surface compounds between alcohols and potassium on Mo 2C/Mo(1 0 0) surface. Analysis of the HREEL spectra of the adsorbed layers suggested that the scission of O–H bond is the primary step in the decompositions of alcohols and we can count with the formation of very stable CH 3O–K and C 2H 5O–K surface species at high potassium coverage. In addition, we can also reckon with the rupture of C–O bonds producing adsorbed CH 3 and C 2H 5 species.