Theoretical investigations on decomposition of HCOOH catalyzed by Pd ₇ cluster

Density functional theory based calculations have been performed to investigate decomposition of HCOOH on a Pd₇ cluster in vacuum and solution. The adsorption of HCOOH on Pd₇ cluster occurs on a layer-by-layer quasi-planar conformation of Pd₇ with 4 atoms on top and 3 atoms below. Possible reaction pathways for the decomposition of HCOOH adsorbed on Pd₇ cluster in vacuum and solution are located and compared in terms of the reaction enengies and barriers. Formic acid prefers to decompose through dehydrogenation rather than dehydrate under the significant effect of solvent. The toxic species, CO generated on Pt surface, could not possibly appear in the catalytic decomposition of formic acid on Pd₇ cluster due to high reaction barrier, thus no poisoning of catalyst would occur on Pd surface. The Pd₇ cluster model rationalizes experimental observation, and the predictions are in good agreement with the ones based on the surface model.