Ethylene versus ethane: A DFT-based selectivity descriptor for efficient catalyst screening

The production of ethylene without its hydrogenation to ethane is a challenge for several catalytic processes. Here, we present a catalyst screening scheme, where the Gibbs free energy difference between the ethylene hydrogenation barrier and ethylene desorption energy is defined as a descriptor for ethylene selectivity. Using plane-wave, dispersion-corrected DFT calculations, we evaluated the descriptor values over the (111) facets of Pt, Pd, and Cu as well as a series of Pt- and Pd-based bimetallic alloys. Our predicted descriptor values indicate that the addition of a Group IB metal (Cu, Ag, or Au) to Pt or Pd improves ethylene selectivity. Ag induces the most significant improvement at 50% while Au has the strongest effect at 75% atomic composition. Pd-based alloys exhibit superior ethylene selectivity over their Pt-based counterparts. Our descriptor model offers an efficient method for the initial screening of catalysts with improved ethylene selectivity.