Density functional theoretical studies on the methanol adsorption and decomposition on Ru(0001) surfaces

Abstract

Periodic density functional theory(DFT) calculations are presented to describe the adsorption and decomposition of CH 3 OH on Ru(0001) surfaces with different coverages, including p(3×2), p(2×2), and p(2×1) unit cells, corresponding to monolayer(ML) coverages of 1/6, 1/4, and 1/2, respectively. The geometries and energies of all species involved in methanol dissociation were analyzed, and the initial decomposition reactions of methanol and the subsequent dehydrogenations reactions of CH 3 O and CH 2 OH were all computed at 1/2, 1/4, and 1/6 ML coverage on the Ru(0001) surface. The results show that coverage exerts some effects on the stable adsorption of CH 3 O, CH 2 OH, and CH 3 , that is, the lower the coverage, the stronger the adsorption. Coverage also exerts effects on the initial decomposition of methanol. C-H bond breakage is favored at 1/2 ML, whereas C-H and O-H bond cleavages are preferred at 1/4 and 1/6 ML on the Ru(0001) surface, respectively. At 1/4 ML coverage on the Ru(0001) surface, the overall reaction mechanism can be written as 9CH 3 OH→3CH 3 O+6CH 2 OH+9H→6CH 2 O+3CHOH+18H→ 7CHO+COH+CH+OH+26H→8CO+C+O+36H.