Abstract:

The reaction pathway of methanol decomposition (CH3OH(s)→CH3O(s)+H(s)→CH2O(s)+2H(s)→CHO(s)+3H(s)→CO(s)+4H(s)) on Pd(111) surfaces was studied using density functional theory (DFT). Geometries of reactants, intermediates, transition states and products were calculated. Adsorption energies of possible species and activation energy barriers of possible elementary reactions involved in the mechanism were obtained in this work. In addition, we studied the reaction mechanism for C—O bond scission in methanol decomposition, which led to the formation of CH3(s) and OH(s). Results show that O—H bond scission (with an activation energy barrier of 103.1 kJ·mol-1) requires less energy than C—O bond scission (with an activation energy barrier of 249.3 kJ·mol-1). The major reaction pathway on Pd(111) surfaces involves O—H bond scission in CH3OH and then a further decomposition of the resultant methoxy intermediate to CO(s) and H(s) via sequential hydrogen abstraction from CH3O(s). O—H bond scission in methanol and hydrogen abstraction from the methoxy group are possible rate-determining steps for this decomposition with activation energy barriers of 103.1 and 106.7 kJ·mol-1, respectively.

Key words: Methanol decomposition, Reaction mechanism, Density functional theory, Transition state