(234g) Mapping the Degree of Rate Control Using Automated Construction of Microkinetic Models with Rmg-Cat

Kinetic parameters for surface reactions can be predicted using a combination of DFT calculations, scaling relations, and machine learning algorithms; however, construction of microkinetic models still requires a knowledge of all the possible, or at least reasonable, reaction pathways. Our recently developed Reaction Mechanism Generator for Heterogeneous Catalysis (RMG-Cat) [1], built upon the well-established open-source RMG software [2], can provide the complete reaction network from user-supplied initial conditions. It can: propose both elementary reactions and new species by applying reaction templates and recipes; estimate thermodynamic and kinetic parameters using databases of DFT calculations, functional-group decision trees, and heuristics; solve governing rate equations; and decide which reaction pathways should be explored further.

Using linear scaling relations RMG-Cat can now estimate adsorbate thermochemistry on a range of hypothetical metal surfaces and construct detailed microkinetic models for any metal surface, with no prior assumption of a rate limiting step. By running simulations with sensitivity analysis, we can now determine the rate limiting step on each surface and can plot a “volcano surface” of the degree of rate control of each reaction as a function of elemental binding energies. We demonstrate this new tool on the catalytic combustion of methane.

[1] Goldsmith, C. F., West, R. H. “Automatic Generation of Microkinetic Mechanisms for Heterogeneous Catalysis” J. Phys. Chem. C. 21 (18), 9970–9981 (2017) https://doi.org/10.1021/acs.jpcc.7b02133
[2] Gao, C. W., Allen, J. W., Green, W. H., West, R. H. "Reaction Mechanism Generator: Automatic construction of chemical kinetic mechanisms". Comput. Phys. Commun., 203, 212-225, (2016) https://doi.org/10.1016/j.cpc.2016.02.013