A Periodic Density Functional Theory Study of the Dehydrogenation of Methanol over Pt(111)

Abstract

Nonlocal gradient-corrected periodic density functional theory calculations were used to examine the dehydrogenation of methanol to CO over the Pt(111) surface. Two decomposition routes were examinedone involving the activation of the O−H bond of methanol to form the methoxide intermediate and the other involving C−H bond activation to form the hydroxymethyl intermediate. These intermediates can subsequently react to form formaldehyde, formyl, and finally CO on the surface. Although these pathways are interesting because of their potential relevance for methanol fuel cells, under UHV conditions, we find that methanol will more likely desorb than react on Pt(111). The barriers for C−H and O−H bond activation were found to be much higher than the measured heat of desorption. This is consistent with experimental evidence. Our results indicate that methanol adsorbs weakly at the atop site on Pt. At 25% surface coverage, the hydroxymethyl (CH2OH), methoxide (CH3O), formaldehyde (HCHO), and formyl (HCO) species...