CHEMISORPTION AND TRANSFORMATION OF CHX FRAGMENTS (X = 0-3) ON A PD(111) SURFACE - A PERIODIC DENSITY-FUNCTIONAL STUDY

The chemisorption of CHx (x = 0-3) fragments on a Pd(111) surface has been studied with density functional periodic calculations. The bindin g energy decreases strongly as the number of PI atoms increases, and t he fragment tends to restore its tetravalency on the surface: carbon p refers a hollow site, the CH fragment is also in a hollow site, the CH 2 is preferentially in a bridge, and the CH3 is on top of a Pd atom. O n the surface the C-H bond cleavages are weakly endothermic, and the m ost stable surface species is CH3. Dehydrogenation to carbon is howeve r possible through bimolecular reactions with simultaneous formation o f CH4.