Effects of co-adsorbed water on different bond cleavages involved in acetic acid decomposition on Pt (111)

• Co-adsorbed water can affect the selectivity and reactivity of heterogeneous catalysts. • The presence of co-adsorbed water generally favors OCO - H bond cleavage over OC - OH bond cleavage. • The presence of co-adsorbed water generally inhibits C - C bond cleavage, except for C - C bond cleavage of deep dehydrogenation intermediates. • For complex reactions, networks with many parallel reaction paths with similar energetic, exceptions to this general trend can have important implications. Acetic acid decomposition on Pt (111) in the presence of co-adsorbed water is a good model system for oxygenate decomposition on Pt (111) in aqueous phase, with application in hydrogen production and biomass conversion. Here we present a density functional theory (DFT) theory calculation of how co-adsorbed water affects different bond cleavages of acetic acid decomposition on Pt (111). The presence of co-adsorbed water generally enhances O H bond cleavage while inhibiting OC O and OC OH bond cleavage. The influence of co-adsorbed water on C H bond cleavage varies the most and depends on the nature of the transition state and how co-adsorbed water stabilizes the initial and final state. Although these trends are useful as general guidance, they are not sufficient to predict the effect on a complex reaction network such as acetic acid decomposition on Pt (111) which has several parallel reaction paths with similar energies. In the absence of co-adsorbed water, the two lowest energy pathways are decarboxylation (DCX) and decarbonylation (DCN) pathways through a common CH 2 COO intermediate, in which the DCX pathway (C H bond cleavage of CH 2 COO) is more favorable than DCN pathway (OC O bond cleavage of CH 2 COO). In the presence of co-adsorbed water, the energy difference between C H bond cleavage and OC O bond cleavage of CH 2 COO increases, suggesting an increase in the favorability of acetic acid decarboxylation (formation of carbon dioxide) over acetic acid decarbonylation (formation of carbon monoxide) on Pt (111).