(453c) A Systematic Method for Including Diffusion between Catalytic Surface Facets in a Mean-Field Microkinetic Model in Cantera

Heterogeneous catalysts are intricate systems with a complex structural morphology that is challenging to model on a first-principles basis [1]. The metal crystals on the support consist of a composition of exposed facets such as terrace and step sites, which depends on the metal and size of the crystal. In mean-field microkinetic models, this morphology is usually neglected due to its complexity. Instead, the microkinetic model is only constructed for a single facet and compared with the experiments [2]. Although a good agreement between experiment and simulation is often achieved after tuning energetic parameters, the actual shape of the crystal needs to be considered for a truly fair comparison. When accounting for the multifaceted nature of the crystal, it is necessary to also include surface diffusion between the different sites. Surface diffusion is an elementary step that follows the typical Arrhenius approach. In this study, we implement surface diffusion into the open-source Cantera [3] toolkit to extend its functionalities for mean-field microkinetic modeling of heterogeneously catalyzed reactions. The software is then used to simulate the temperature-programmed desorption (TPD) of CO₂ from supported Ni catalysts and compared with experimental results. Including surface diffusion in the microkinetic model significantly affects the predicted desorption profiles. This newly implemented capability enables the computational modeling of molecular diffusion across multiple surfaces or catalyst facets for various chemical processes.

References:

1. Wehinger, G.D., Ambrosetti, M., Kreitz, B., et al. Eng. Res. Des. 184 (2022)
2. Kreitz, B., Lott, P., Bae, J., et al. ACS Catal. 12, (2022)
3. Goodwin D.G., Moffat, H.K., Schoegl I., Speth R.L. and Weber B.W. V2.6.0 (2022)