Density functional study of methoxide decomposition on PdZn(100)

Reactants, products and transition state species involved in the decomposition of methoxide, CH₃O to CH₂O + H and CH ₃ + O fragments on the PdZn(100) surface have been studied theoretically. We used periodic slab models and a density functional method and compared our results to those for the corresponding complexes on the more compact PdZn(111) surface investigated earlier. On PdZn(100), both C-H and C-O bond scission reactions of CH₃O were found to be somewhat more endothermic than on the (111) surface. Transition state structures for both cleavage reactions are similar to their PdZn(111) analogues. Similarly to PdZn(111), C-H bond scission of methoxide is kinetically favored on PdZn(100) over C-O bond breaking. However, even the activation barrier for C-H bond breaking on PdZn(100) surface is rather high. Thus, defects most probably are responsible for methoxide decomposition on PdZn catalysts.