Density Functional Investigation of Methanol Dehydrogenation on Pd(111)

Methanol dehydrogenation to CO and H on Pd(111) is systematically investigated using self-consistent periodic density functional theory (DFT). All possible intermediates involved are calculated. Methanol and formaldehyde adsorb weakly on the Pd(111) surface because they are saturated molecules. CO and H prefer 3-fold sites with the adsorption energies of 41.6 and 64.4 kcal/mol. CH 3 O binds stably at 3-fold and bridge sites. Most of the other intermediates are inclined to adsorb to the surface with the sp 3 configuration of the carbon atom and a hydroxyl-like configuration for O, i.e., top (η 1 -C) for CH 2 OH, bridge (η 2 -C) for CHOH, 3-fold (η 3 -C) for COH, bridge (η 1 -C−η 1 -O) for CH 2 O, and 3-fold (η 2 -C−η 1 -O) for CHO. All possible dehydrogenation pathways are calculated and four different routes via initial O−H and C−H bond scissions are found. The theoretical calculations indicate the initial C−H bond scission is more favorable for methanol decomposition, while O−H bond scission is preferable to C−H bond scission for CH 2 OH and CHOH, and the most possible dehydrogenation pathway on Pd(111) thus takes place via CH 3 OH → CH 2 OH → CH 2 O → CHO → CO.