Ultraviolet photoemission and thermal desorption studies of the chemisorption and decomposition of methanol on potassium‐dosed Rh(111) Available to Purchase

The interaction of methanol with potassium‐dosed (up to monolayer) Rh(111) surface has been studied by means of thermal desorption, ultraviolet photoemission (He ii) spectroscopy and work function measurements. Preadsorbed potassium significantly influenced the adsorption, desorption, and stability of CH₃OH on this Rh surface, but the pathway of the dissociation of CH₃OH and its surface decomposition were not altered. An increase (6–10 kJ/mol) in the binding energy of chemisorbed CH₃OH was found even in the low potassium coverage range, θ_K=0.05–0.26. At higher potassium coverages (θ_K=0.36, monolayer), where K exhibits mainly metallic character, the relative amount of irreversibly adsorbed methanol was greatly increased. In this case methoxy species was detected by He ii photoemission studies: its complete decomposition occurred at around 492–505 K. The stabilization of the methoxy species was reflected in the high temperature for the evolution of H₂(T_P=515 K), too. In the interpretation of the data a direct chemical interaction between methanol and potassium and the formation of a stable potassium methoxide is proposed.