New Insight into CO Formation during HCOOH Oxidation on Pt(111): Intermolecular Dehydration of HCOOH Dimers

Density functional theory simulations were performed to investigate CO formation during HCOOH oxidation on the Pt(111) surface in aqueous phase, through the intermolecular dehydrations of various HCOOH dimer models. The formation of CO that is found to poison Pt catalysts proceeds via four major intermolecular dehydration pathways as determined by varying initial HCOOH dimer structures. The computed rate-determining energy barriers of those four pathways are low, suggesting the kinetically and thermodynamically facile formation of intermediates and CO. This work demonstrates that the presence of HCOOH dimers accounts for the easy CO poisoning of Pt-based catalysts, and clarifies the controversy on the intermediates and mechanisms of CO formation found in different HCOOH oxidation experiments.