Microkinetic models serve as a potent tool for characterizing and quantifying the kinetics of a catalytic reaction on a surface. Model parameters are commonly derived from density functional theory calculations on finite-sized supercells of a single coverage [1]. The coverage implicit in a supercell model is often not representative of the coverages predicted from the corresponding microkinetic model. Lateral interactions between adsorbates that emerge at finite coverages have been shown to affect reaction activation energies,rates and rate orders [2][3][4][5] and to impact relative performance of different materials for a particular reaction [6][7].<br/><br/>In this work, we probe the consequences of adsorbate-adsorbate interactions within a simplified two-step reaction network inspired by ammonia synthesis and NO oxidation, as shown in Fig. 1. We examine how rates, rate orders, apparent activation energies, and Sabatier plots respond to increasing inclusion of explicit lateral adsorbate interactions using a lattice-based kinetic Monte Carlo (kMC) framework. We subsequently formulate and solve the same kinetic system within a coverage-explicit mean field model. We highlight the performance of conventional parameterization schemes relative to the kMC results and identify ensuing opportunities for improving upon those mean-field parameterizations to yield rates and rate sensitivities more faithful to the underlying adsorbate interactions.

Performance assessment of explicit and implicit representations of coverage dependence on the microkinetics of catalytic reactions

ACS Spring Meeting 2021

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