Finite Bias Calculations to Model Interface Dipoles in Electrochemical Cells at the Atomic Scale

The structure of an electrochemical interface is not determined by any external electrostatic field, but rather by external chemical potentials. This paper demonstrates that the electric double layer should be understood fundamentally as an internal electric field set up by the atomic structure to satisfy the thermodynamic constraints imposed by the environment. This is captured by the generalized computational hydrogen electrode model, which enables us to make efficient first-principles calculations of atomic scale properties of the electrochemical interface

First Principles Micro-kinetic Model of Catalytic Non-oxidative Dehydrogenation of Ethane over Close-packed Metallic Facets

Catalytic dehydrogenation of light alkanes may other more efficient routes to selectively producing light olefins, which are some of the most important chemical building blocks in the industry, in terms of scale. We present a descriptor based micro-kinetic model of the trends in selectivity and activity of non-oxidative dehydrogenation of ethane over close-packed metal facets and through varied reaction conditions. Our model predicts and explains the experimentally observed promotion effect on turnover rate from co-feeding hydrogen as an effect of the shifting equilibria in steady state. At low conversion reaction conditions over Pt, the path to ethene goes through ethane dehydrogenation to ethyl, CH 3 CH 2 *, then to ethene while the non-selective pathway to methane and deeply dehydrogenated species is predicted to go through dehydrogenation via CH 3 CH*. This implies that the desorption step of ethene is not the limiting step for selectivity and that geometric effects that stabilize CH 2 CH 2 * compared to CH 3 CH* are desirable properties of a better catalyst. Removing reactive bridge and 3-fold sites facilitates this, which may be achievable by sufficient concentrations of tin in platinum. The included model code furthermore provides a base for easy tuning and for expanding the study to other thermodynamic conditions, other facets, alloys or the reaction network to longer hydrocarbons or to oxidative pathways. </div

First principles micro-kinetic model of catalytic non-oxidative dehydrogenation of ethane over close-packed metallic facets

Catalytic dehydrogenation of light alkanes may other more efficient routes to selectively producing light olefins, which are some of the most important chemical building blocks in the industry, in terms of scale. We present a descriptor based micro-kinetic model of the trends in selectivity and activity of non-oxidative dehydrogenation of ethane over close-packed metal facets and through varied reaction conditions. Our model predicts and explains the experimentally observed promotion effect on turnover rate from co-feeding hydrogen as an effect of the shifting equilibria in steady state. At low conversion reaction conditions over Pt, the path to ethene goes through ethane dehydrogenation to ethyl, CH 3 CH 2 *, then to ethene while the non-selective pathway to methane and deeply dehydrogenated species is predicted to go through dehydrogenation via CH 3 CH*. This implies that the desorption step of ethene is not the limiting step for selectivity and that geometric effects that stabilize CH 2 CH 2 * compared to CH 3 CH* are desirable properties of a better catalyst. Removing reactive bridge and 3-fold sites facilitates this, which may be achievable by sufficient concentrations of tin in platinum. The included model code furthermore provides a base for easy tuning and for expanding the study to other thermodynamic conditions, other facets, alloys or the reaction network to longer hydrocarbons or to oxidative pathways. </div