The interaction of methanol with Ru(001)

Abstract

The adsorption, desorption, and decomposition of methanol on a clean Ru(001) surface at 85 K has been examined with electron energy loss spectroscopy, multiple mass thermal desorption spectroscopy, low energy electron diffraction, and a work function probe. Methanol adsorbs readily on Ru(001) and is found to decompose at submonolayer coverages even at low temperature (85 K). Two decomposition pathways are observed: oxygen–hydrogen bond breaking (CH3OH→CH3O–M+H–M) and carbon–oxygen bond breaking (CH3OH→H2O+C–M+2H–M). The methoxy species either recombines with hydrogen and desorbs as methanol between 220 and 250 K via second order reaction kinetics (n=1.85; E*D≂14 kcal/mol; ν(2)=10−2 cm−2 s−1); or further decomposes to form carbon monoxide and hydrogen. The conversion of the methoxy species into carbon monoxide begins at 220 K and is completed at 300 K. The methoxy conversion is accompanied by the gradual formation of a p(2×2) LEED pattern which disappears after CO desorption. The second reaction channel, i.e., C–O bond breaking, results in the formation of water, which desorbs at 210 K, and in surface carbon, which was detected with oxygen titration. The results are discussed and compared to methanol decomposition on palladium and nickel and demonstrate the unique ability of Ruthenium for both C–O bond cleavage and formation of hydrogenatable methoxy species.