Structure-Dependent Microkinetic Modeling of the CO2 Desorption with Surface Diffusion

The interaction of CO2 with Ni catalysts is important for many industrial processes like methanation, which is known to be structure sensitive. Consequently, structure-dependent multiscale modeling is required to accurately capture the interaction of CO2 with the various Ni facets and to provide accurate atomistic insights. While mean-field multiscale models can be constructed that account for multiple active facets, almost all of these studies neglect the diffusion of adsorbates between the facets. In this study, we close the gap by extending the open-source Cantera toolkit with capabilities for surface diffusion in mean-field microkinetic models, making it the first widely adopted software tool that includes these features. We developed a thermodynamically consistent microkinetic model for a Ni nanoparticle consisting of Ni(111), Ni(100), Ni(211), and Ni(110) using data from DFT calculations and single-crystal experiments to unravel the interaction of CO2 with these facets through the simulation of temperature-programmed desorption profiles. Including surface diffusion and coverage effects into the mean-field microkinetic model leads to a significantly improved agreement between experiments from a Ni/SiO2 catalyst and the simulations. Using a rigorous correlated uncertainty quantification of all structural and energetic parameters, we found a detailed chemical model within the uncertainty space that is in excellent agreement with the recorded CO2 desorption profile. This model highlights that Ni(110), which contributes only to a small extent to the overall Ni surface area, dominates the desorption pattern and that surface diffusion reactions play a crucial role. The implemented surface diffusion into Cantera is generic and can be applied to other (mixed) metal nanoparticles and metal/metal oxide interfaces, providing a step towards closing the material gap.