Quantifying the Impact of Parametric Uncertainty on Automatic Mechanism Generation for CO₂ Hydrogenation on Ni(111)

Abstract

Automatic mechanism generation is used to determine mechanisms for the CO 2 hydrogenation on Ni(111) in a two-stage process while considering the correlated uncertainty in DFT-based energetic parameters systematically. In a coarse stage, all the possible chemistry is explored with gas-phase products down to the ppb level, while a refined stage discovers the core methanation submechanism. Five thousand unique mechanisms were generated, which contain minor perturbations in all parameters. Global uncertainty assessment, global sensitivity analysis, and degree of rate control analysis are performed to study the effect of this parametric uncertainty on the microkinetic model predictions. Comparison of the model predictions with experimental data on a Ni/SiO 2 catalyst find a feasible set of microkinetic mechanisms within the correlated uncertainty space that are in quantitative agreement with the measured data, without relying on explicit parameter optimization. Global uncertainty and sensitivity analyses provide tools to determine the pathways and key factors that control the methanation activity within the parameter space. Together, these methods reveal that the degree of rate control approach can be misleading if parametric uncertainty is not considered. The procedure of considering uncertainties in the automated mechanism generation is not unique to CO 2 methanation and can be easily extended to other challenging heterogeneously catalyzed reactions.

Detailed microkinetics for the oxidation of exhaust gas emissions through automated mechanism generation

“…BEP relations have been proven to be universal for surface reaction mechanisms in a variety of studies and predictions are suitably accurate. 6,[59][60][61] Therefore, the usage of training reactions was turned off, and we relied exclusively on BEP relations for the reaction families to estimate the reaction kinetics of all elementary steps, similar to the procedure reported by Kreitz et al 32 Parameters for the BEP relations are based on values reported in the literature 32,[62][63][64][65][66][67] and are summarized in Table S2. In the generated mechanisms, we provide only the Arrhenius parameters for the forward rate constant; the reverse rate constant is computed from the equilibrium constant, which is determined from the thermochemistry of the adsorbates.…”

“…[24][25][26][27][28] However, RMG has only recently been used for heterogeneously catalyzed reactions. [29][30][31][32] The publications on the heterogeneous catalysis branch of RMG are focused on demonstrating new features rather than developing a microkinetic model suitable to describe experimental results. Blöndal et al 30 developed a thermochemistry database for adsorbates on the Pt(111) surface and showed that RMG could be used to generate mechanisms for coupled homogeneous/heterogeneous reactions for methane oxidation.…”

“…In order to estimate the thermochemistry on all other metals, Mazeau et al 31 have implemented linear scaling relations 33 in RMG. Recently, some of the authors demonstrated the capability of RMG to generate mechanisms for the CO 2 methanation on Ni(111) 32,34 while considering the correlated uncertainties in the energetic parameters. 32 In the study of Kreitz et al, 32 the generated mechanism for the methanation on Ni(111) was in good agreement with temperature-scanning experiments from a Ni/SiO 2 catalyst.…”

Adsorbate Partition Functions via Phase Space Integration: Quantifying the Effect of Translational Anharmonicity on Thermodynamic Properties

“…The results of these calculations will be incorporated into the Active Thermochemical Tables (ATcT) of Argonne National Laboratory as it expands to include thermophysical properties for adsorbates. Finally, the improved thermodynamic properties will be included both in the database and in the group rules used by the automatic microkinetics software for heterogeneous catalysis, RMG. ,− …”

Trendbericht Technische Chemie 2022

“…RMG haben Mazeau und Kollegen:innen genutzt, um Katalysatoren für die partielle CH 4 -Oxidation zu screenen 56). Kreitz und Co-Autoren:innen57) haben mit RMG Mechanismen für die Die Nachrichten online weiter blättern mit der neuen GDCh-App! www.gdch.app 70.…”