Density functional theory (DFT) method was employed to investigate the adsorption and decomposition mechanisms of CH3OH on Pd (100) surface. Different kinds of possible adsorption modes of relevant intermediates on the surface were identified. It was found that CH3OH and CH2OH prefers to adsorb on the top site, CH3O, CHOH and CO occupy preferentially on the bridge site, while CH2O, CHO, COH and H species adsorb on the hollow site. The adsorption energies of all species exhibit the following trend: CH3OH < CH2O < CH3O < CO < CH2OH < H < CHO < CHOH < COH. Subsequently, four possible dissociation pathways of CH3OH via initial O-H and C-H bond scissions were proposed and studied systematically. The transition states, energy barriers and reaction energies were calculated to explore the dehydrogenation mechanisms of CH3OH on Pd (100) surface. It was indicated that the scission of C H bond is more favorable for CH3OH and CH2OH and the H-O bond cleavage is easier for CHOH. The path 2 (CH3OH-CH2OH-CHOH-CHO-CO) is the most possible dehydrogenation pathway, where the highest energy barrier of CH3OH dissociation makes it to be the rate-determining step of the whole dehydrogenation reaction. (C) 2015 Elsevier B.V. All rights reserved.