Investigation of\nEthane Dehydrogenation and Hydrogenolysis\non Pt(111), Pt(211), and Pt(100): Bayesian Quantification and Correction\nof DFT-Based Enthalpic and Entropic Uncertainties

Computational investigations of heterogeneously catalyzed\nreactions\nusing density functional theory (DFT) are often inaccurate, largely\ndue to uncertainties in the choice of DFT functional (enthalpic uncertainty)\nand approximations for modeling adsorbate movement along the catalyst\nsurface (entropic uncertainty). This work illustrates that both uncertainties\nare significant in the investigation of ethane dehydrogenation (EDH)\nand hydrogenolysis on Pt catalysts by considering the complete deconstruction\nof ethane on Pt(111), Pt(211), and Pt(100) using microkinetic modeling\n(MKM). Hence, this work uses both noncalibrated and Bayesian-calibrated\nMKMs to quantify and correct inaccuracies in macroscopic properties\ndue to both uncertainties. A Bayesian approach to the correction of\nentropic errors was introduced using a “Modified Fermi Function\n(MFF)” to calibrate between the two bounds of entropy represented\nby the harmonic oscillator (HO) and free translator (FT) approximations.\nRegardless of enthalpic and entropic uncertainties, all three surfaces\nare capable of ethane activation; however, Pt(211) was found to be\nthe most active and is largely responsible for methane production.\nNext, Pt(111) is largely responsible for acetylene production, and\nPt(100) has the highest ethylene selectivity but is most susceptible\nto coking. By comparison of different calibrated models, the FT entropy\napproximation was found to better describe EDH under typical experimental\nconditions. Statistical evidence was found to support Pt(111) as the\n active site for EDH, assuming that one single site is responsible\nfor the chemistry. On the three surfaces, competing second dehydrogenations\nto CH<sub>2</sub>CH<sub>2</sub> and CH<sub>3</sub>CH were observed\nas well as isomerization of CH<sub>3</sub>CH back to CH<sub>2</sub>CH<sub>2</sub> and deeper dehydrogenation of CH<sub>3</sub>CH. C–C\ncleavage was found to largely proceed via the CH<sub>3</sub>C intermediate\non Pt(100) and Pt(111), while on Pt(211), it was via both CHC and\nCH<sub>3</sub>C.