A review of multiscale modeling of metal-catalyzed reactions: Mechanism development for complexity and emergent behavior

Abstract

We review and provide a perspective on multiscale modeling of catalytic reactions with emphasis on mechanism development and application to complex and emergent systems. We start with an overview of length and time scales, objectives, and challenges in first-principles modeling of reactive systems. Subsequently, we review various methods that ensure thermodynamic consistency of mean-field microkinetic models. Next, we describe estimation of reaction rate constants via quantum mechanical and statistical-mechanical methods as well as semi-empirical methods. Among the latter, we discuss the bond-order conservation method for thermochemistry and activation energy estimation. In addition, we review the newly developed group-additivity method on adsorbate/metal systems and linear free energy or Brønsted-Evans-Polanyi (BEP) relations, and their parameterization using DFT calculations to generate databases of activation energies and reaction free energies. Linear scaling relations, which can enable transfer of reaction energetics among metals, are discussed. Computation-driven catalyst design is reviewed and a new platform for discovery of materials with emergent behavior is introduced. The effect of parameter uncertainty on catalyst design is discussed; it is shown that adsorbateadsorbate interactions can profoundly impact materials design. Spatiotemporal averaging of microscopic events via the kinetic Monte Carlo method for realistic reaction mechanisms is discussed as an alternative to mean-field modeling. A hierarchical multiscale modeling strategy is proposed as a means of addressing (some of) the complexity of catalytic reactions. Structurebased microkinetic modeling is next reviewed to account for nanoparticle size and shape effects and structure sensitivity of catalytic reactions. It is hypothesized that catalysts with multiple sites of comparable activity can exhibit structure sensitivity that depends strongly on operating conditions. It is shown that two descriptor models are necessary to describe the thermochemistry of adsorbates on nanoparticles. Multiscale and accelerated methods for computing free energies in solution, while accounting explicitly for solvent effects in catalytic reactions, are briefly touched upon with the acid catalyzed dehydration of fructose in water as an example. The above methods are illustrated with several reactions, such as the CO oxidation on Au; the hydrogenation of ethylene and hydrogenolysis of ethane on Pt; the glycerol decomposition to syngas on Pt-based materials; the NH 3 decomposition on single metals and bimetallics; and the dehydration of fructose in water. Finally, we provide a summary and outlook.

A nature-inspired approach to reactor and catalysis engineering

“…[36]. Simulation relies on a range of modeling approaches [37], which are increasingly multiscale [38,39]. Recent possibilities to control pore network properties at multiple length scales via new synthesis methods [40,41,42 ] should be accompanied by theoretical optimization.…”

Microkinetic modeling and analysis of ethanol partial oxidation and reforming reaction pathways on platinum at short contact times

“…A mean-field approximation is used in this model but a kinetic Monte Carlo approach to modeling the metal surface as individual sites and is updated in real time would make the model more realistic [92]. This approach would allow for the proximity of adsorbates to be considered as well as different facets of the metal and their corresponding differences in binding energies.…”

kmos: A lattice kinetic Monte Carlo framework

“…[1][2][3][4][5][6][7][8] Such models have to span a range of scales in length and time, starting with the making and breaking of the individual chemical bonds at the electronic structure level, over the mesoscopic interplay of the various elementary reactions in the reaction network, to the heat and mass transport at the macroscopic (reactor) scale. [9][10][11][12][13][14][15] To achieve this, state-of-the-art multi-scale models resort to a hierarchical combination of different methodology. The current framework for the mesoscopic level are microkinetic approaches evaluating a (Markovian) master equation (vide infra).…”