Decomposition of Furan on Pd(111)

Periodic density functional theory calculations (GGA-PBE) have been performed to investigate the mechanism for the decomposition of furan up to CO formation on the Pd(111) surface. At 1/9 ML coverage, furan adsorbs with its molecular plane parallel to the surface in several states with nearly identical adsorption energies of ?1.0?eV. The decomposition of furan begins with the opening of the ring at the C?CO position with an activation barrier of E _a ?=?0.82?eV, which yields a C₄H₄O aldehyde species that rapidly loses the ?? H to form C₄H₃O (E _a ?=?0.40?eV). C₄H₃O further dehydrogenates at the ?? position to form C₄H₂O (E _a ?=?0.83?eV), before the ???C?? C?CC bond dissociates (E _a ?=?1.08?eV) to form CO. Each step is the lowest-barrier dissociation step in the respective species. A simple kinetic analysis suggests that furan decomposition begins at 240?C270?K and is mostly complete by 320?K, in close agreement with previous experiments. It is suggested that the C₄H₂O intermediate delays the decarbonylation step up to 350?K.