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WIREs Comput Mol Sci
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Concepts, models, and methods in computational heterogeneous catalysis illustrated through CO2 conversion

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Abstract Theoretical investigations and computational studies have notoriously contributed to the development of our understanding of heterogeneous catalysis during the last decades, when powerful computers have become generally available and efficient codes have been written that can make use of the new highly parallel architectures. The outcomes of these studies have shown not only a predictive character of theory but also provide inputs to experimentalists to rationalize their experimental observations and even to design new and improved catalysts. In this review, we critically describe the advances in computational heterogeneous catalysis from different viewpoints. We firstly focus on modeling because it constitutes the first key step in heterogenous catalysis where the systems involved are tremendously complex. A realistic description of the active sites needs to be accurately achieved to produce trustable results. Secondly, we review the techniques used to explore the potential energy landscape and how the information thus obtained can be used to bridge the gap between atomistic insight and macroscale experimental observations. This leads to the description of methods that can describe the kinetic aspects of catalysis, which essentially encompass microkinetic modeling and kinetic Monte Carlo simulations. The puissance of computer simulations in heterogeneous catalysis is further illustrated by choosing CO2 conversion catalyzed by different materials for most of which a comparison between computational information and experimental data is available. Finally, remaining challenges and a near future outlook of computational heterogeneous catalysis are provided. This article is categorized under: Structure and Mechanism > Computational Materials Science Structure and Mechanism > Reaction Mechanisms and Catalysis
Different pathways to activate CO2 over catalytic surfaces upon substrate → CO2 electron transfer to form an active bent moiety. Reprinted with permission from Ref. 191
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(a) Scheme of a solid surface in contact with the surrounding CO2 gas phase characterized by defined T and p. Generic free energy plot for a surface in equilibrium with a surrounding CO2 gas phase. (b) Schematic representation of the bottom‐up computational strategy that aims to propagate the predictive power of first‐principles techniques up to increasing length and time scales providing insights into the ongoing surface chemistry over a wide range of temperature and pressure conditions. (c) Brønsted–Evans–Polanyi (BEP) relationships between the activation energy for CO2 dissociation into chemisorbed CO and O species on several low‐index transition metal surfaces and the reaction energy (left panel) or the sum of the adsorption energies of the products of the dissociation reaction (right panel). Graphs made with data from Ref. 200
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(a) Schematic view of metal NP (gray spheres) supported on a rock‐salt oxide surface (light and blue spheres). Notice how the substrate surface features terraces and steps, with defects. Nearby images represent different models used to represent different parts of the whole system, including cluster models (brown spheres), nanocrystallites (green spheres), cluster models showing substrate defects (orange and dark blue spheres), regular surface slab models (yellow and cyan spheres), and vicinal surfaces (pink and violet spheres). (b) Schematic representation of a given property evolution with size, here denoted as metal cluster and NP models of increasing size, revealing the oscillation of the property value with size in the non‐scalable region, and the linear evolution toward the bulk from the scalable region onward
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Schematic view of time and size scales, and typical regions of applicability of different computational chemistry methods. Images nearby regions show atomic model examples
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Gibbs free energy profile of the dry reforming of CH4 catalyzed by the (0001) surface of partially oxidized Mo2C MXene at 1073 K, with CH4 and CO2 partial pressures of 1 bar. Insets show top views of critical reaction steps, where pink, red, black, and white spheres denote Mo, O, C, and H atoms, respectively
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Kinetic phase diagram (top) for Hfn + 1Cn MXene (0001) surfaces with results for HfC(001) and HfC(111) surfaces included for comparison. White dashed dot lines stand for the atmospheric of 40 Pa, at the exhaust gases of 15 × 103, and at the pure CO2 stream generation of 105 Pa. Atomic top and sides views of CO2 adsorbed on sites of MXene (0001) surfaces and TMC(111) surfaces, where top and inner layer M atoms are shown as dark and light blue spheres, respectively, whereas inner carbon layer is represented by dark yellow spheres. The CO2 molecule oxygen and carbon atoms are represented by red and brown spheres, respectively. Adapted from data of Ref. 266
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Gibbs free energy barriers, in eV, and side atomic views for different reaction steps through the COOH formation or the direct CO2 dissociation and posterior CO successive hydrogenations toward CH3OH, as computed on the Cu4@δ‐MoC(001) (left) and δ‐MoC(001) (right) surface models. Based on the data from Ref. 245. Mo, C, Cu, O, and H atoms are shown as violet, green, orange, red, and white spheres, respectively
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(a)Top (top) and side (bottom) views of activated, bent CO2, adsorbed on a six‐layered, 3 relaxed +3 fixed, (2√2 × 2√2)R45° TiC(001) slab model, either on a TopC (left) or an MMC (right) conformation. Carbon, oxygen, and titanium atoms are shown as brown, red, and blue spheres, respectively. Notice that fixed layers are shown in light colors. (b) Gibbs free energy surfaces of the CO2 dissociation to CO + O from most stable sites on different α‐Mo2C surfaces at the working conditions of T = 600 K, = = 0.2 bar, pCO= = 1 mbar. Based on the data from Ref. 89
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Structure and Mechanism > Reaction Mechanisms and Catalysis
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