Methanol oxidation on the Au(310) surface: A theoretical study

This work establishes a comprehensive analysis of the role of steps and kinks of the Au(3 1 0) surface in the generation of active oxygen species and elucidates the reaction pathway for methanol oxidation to formaldehyde. We have considered two possibilities for the O-O bond splitting in molecular O-2: via a dissociative O-2 adsorption or a direct reaction of O-2 with methanol. Both reaction pathways more favorably take place on the step edges of Au(3 1 0) than on flat Au(1 1 1). Depending on the adsorption positions of O-2, different dissociation pathways are possible, where the most favored path shows a substantially lower activation barrier compared to the flat gold surface. Atomic oxygen generated on the surface, prefers to build O-Au-O fragments with stronger binding to the surface than individually adsorbed O. The reaction pathways for methanol reaction with O and O-2 have been analyzed and compared. The direct reaction of methanol with molecular oxygen (an associative mechanism) proceeds via a formation of the OOH intermediate and its further dissociation to O and OH. This reaction sequence has low activation barriers of 0.3-0.4 eV and therefore should be preferred over O-2 dissociation to atomic O and the following reaction of O with methanol. By analogy, O-2 can react with water generating OOH with similarly low activation barriers. We have supported the proposed associative mechanism by microkinetic modeling. (C) 2018 Elsevier Inc. All rights reserved.