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 CH3+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.