Our present study indicates that solvent effect can alter CH3OH decomposition pathways and identifies for the first time the presence of a dual reaction mechanism for CH3OH heterolytic decomposition that proceeds through formation of CH2OH and CH3O intermediates, whereas only initial C-H bond dissociation mechanism is identified in homolytic pathways. Furthermore, the homolytic and heterolytic pathways may be able to occur simultaneously on Pt(111) based on our DFT calculations. The present study can provide a new insight into modeling dehydrogenation reactions in aqueous-phase and help to achieve the ultimate goal of the design of Pt-based alloy electrocatalysts for CH3OH decomposition. (C) 2017 Elsevier B.V. All rights reserved.