Predicting and Comparing C–M and O–M Bond Strengths for Adsorption on Transition Metal Surfaces

Understanding which surface properties control adsorption on metal surfaces has long been a primary goal in surface science and catalysis, for both fundamental and technological reasons. Moreover, for the purposes of designing catalysts for enhanced selectivity, it can be desirable to understand surface properties that lead to significant differences in adsorption energies of hydrocarbons and oxygenates. In this work, expressions for predicting adsorption energies of CH 3 and OH are developed, based in part on screening a large number of possible predictors. These expressions include the d-band center, d-band filling, and matrix coupling element, which are well-known in the literature, as well as the relatively unstudied p-band center. These expressions are also applied to other adsorbates, including alkyls, alkoxides, C, O, and H, allowing elucidation of how the adsorbate structure affects the adsorption energy. While all alkyls behave similarly and all alkoxides behave similarly, there are significant differences between alkyls and alkoxides. In particular, adsorbate–surface coupling is net attractive for hydrocarbons but net repulsive for oxygenates, likely due to the deeper valence states on O atoms. As demonstrated within the context of the partial oxidation of ethylene, this difference can potentially be used to rapidly screen catalysts for improved selectivity based on the values of simple electronic structure parameters.