First-Principles Study of Structure Sensitivity of Ethylene Glycol Conversion on Platinum

Periodic density functional theory (DFT) calculations are used to investigate the structure sensitivity of ethylene glycol (EG) decomposition on terraced and stepped platinum surfaces, including Pt(111) and Pt(211). On both surfaces, the binding energies of lightly dehydrogenated intermediates resulting from C-H bond scission in EG are typically stronger than the binding energies of intermediates associated with O-H bond breaking, and the corresponding kinetic trends generally track the thermochemical results. C-C and C-O bond cleavage have significantly higher barriers than dehydrogenation until relatively late in the dehydrogenation reaction network, and the transition state energies associated with C-C bond scission decrease almost monotonically with increasing levels of EG dehydrogenation, whereas the transition state energies of C-O bond breaking first decrease and then increase slightly. The most favorable reaction pathways for EG decomposition on Pt(111) and Pt(211) are very similar, with CO and H-2 as the main predicted products. However, Pt(211) shows substantially stronger binding of intermediates than does Pt(111). These results imply that platinum catalysts for EG conversion are likely to be relatively structure-sensitive in terms of activity but less sensitive in terms of selectivity. The results also demonstrate that linear relationships for prediction of both binding energies of dehydrogenated intermediates and barriers of elementary steps, which have been previously derived on close-packed terraces, are also found on steps, providing an important extension of these scaling and correlation principles to defected geometries. These relationships could, in turn, be used to accelerate the computational analysis of related complex reaction networks on undercoordinated surface features.