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Open accessJournal ArticleDOI: 10.1021/ACS.ACCOUNTS.0C00857

The Genesis of Molecular Volcano Plots.

02 Mar 2021-Accounts of Chemical Research (American Chemical Society)-Vol. 54, Iss: 5, pp 1107-1117
Abstract: ConspectusFor the past two decades, linear free energy scaling relationships and volcano plots have seen frequent use as computational tools that aid in understanding and predicting the catalytic behavior of heterogeneous and electrocatalysts Based on Sabatier's principle, which states that a catalyst should bind a substrate neither too strongly nor too weakly, volcano plots provide an estimate of catalytic performance (eg, overpotential, catalytic cycle thermodynamics/kinetics, etc) through knowledge of a descriptor variable By the use of linear free energy scaling relationships, the value of this descriptor is employed to estimate the relative energies of other catalytic cycle intermediates/transition states Postprocessing of these relationships leads to a volcano curve that reveals the anticipated performance of each catalyst, with the best species appearing on or near the peak or plateau While the origin of volcanoes is undoubtedly rooted in examining heterogeneously catalyzed reactions, only recently has this concept been transferred to the realm of homogeneous catalysis This Account summarizes the work done by our group in implementing and refining "molecular volcano plots" for use in analyzing and predicting the behavior of homogeneous catalystsWe begin by taking the reader through the initial proof-of-principle study that transferred the model from heterogeneous to homogeneous catalysis by examining thermodynamic aspects of a Suzuki-Miyaura cross-coupling reaction By establishing linear free energy scaling relationships and reproducing the volcano shape, we definitively showed that volcano plots are also valid for homogeneous systems On the basis of this key finding, we further illustrate how unified pictures of C-C cross-coupling thermodynamics were created using three-dimensional molecular volcanoesThe second section highlights an important transformation from "thermodynamic" to "kinetic" volcanoes by using the descriptor variable to directly estimate transition state barriers Taking this idea further, we demonstrate how volcanoes can be used to directly predict an experimental observable, the turnover frequency Discussion is also provided on how different flavors of molecular volcanoes can be used to analyze aspects of homogeneous catalysis of interest to experimentalists, such as determining the product selectivity and probing the substrate scopeThe third section focuses on incorporating machine learning approaches into molecular volcanoes and invoking big-data-type approaches in the analysis of catalytic behavior Specifically, we illustrate how machine learning can be used to predict the value of the descriptor variable, which facilitates nearly instantaneous screening of thousands of catalysts With the large amount of data created from the machine learning/volcano plot tandem, we show how the resulting database can be mined to garner an enhanced understanding of catalytic processes Emphasis is also placed on the latest generation of augmented volcano plots, which differ fundamentally from earlier volcanoes by elimination of the use of linear free energy scaling relationships and by assessment of the similarity of the complete catalytic cycle energy profile to that for an ideal reference species that is used to discriminate catalytic performanceWe conclude by examining a handful of applications of molecular volcano plots to interesting problems in homogeneous catalysis and offering thoughts on the future prospects and uses of this new set of tools

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Topics: Volcano plot (55%)
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9 results found


Journal ArticleDOI: 10.1016/J.JCAT.2021.09.014
Abstract: Combining spectroscopic and transient kinetic techniques provides access to the identification and quantification of active sites and corresponding turnover frequencies of catalyzed reactions [1] . Ab initio calculated rate coefficients combined with network generation codes allow so-called microkinetic models accounting for all relevant elementary steps of complex reaction networks. Computational Fluid Dynamics (CFD) account for the scale-dependent transport of mass, energy and momentum and, hence, renders the design of an industrial process based on the intrinsic chemical kinetics possible. These theoretical and experimental achievements cannot be a substitute for the insights provided by the analysis of a catalytic cycle in terms of a limited number of kinetically significant steps [2] . We analyse the kinetics of a single-path reaction represented as a closed sequence of two steps [3] . We discuss some examples of chemical looping processes providing, in contrast to catalytic technology, the possibility to perform the steps of a closed sequence at different conditions.

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Topics: Chemical process (52%)

2 Citations


Open accessJournal ArticleDOI: 10.1021/ACS.JPCLETT.1C02852
Abstract: We demonstrate an alternative, data-driven approach to uncovering structure-property relationships for the rational design of heterobimetallic transition-metal complexes that exhibit metal-metal bonding. We tailor graph-based representations of the metal-local environment for these complexes for use in multiple linear regression and kernel ridge regression (KRR) models. We curate a set of 28 experimentally characterized complexes to develop a multiple linear regression model for oxidation potentials. We achieve good accuracy (mean absolute error of 0.25 V) and preserve transferability to unseen experimental data with a new ligand structure. We also train a KRR model on a subset of 330 structurally characterized heterobimetallics to predict the degree of metal-metal bonding. This KRR model predicts relative metal-metal bond lengths in the test set to within 5%, and analysis of key features reveals the fundamental atomic contributions (e.g., the valence electron configuration) that most strongly influence the behavior of these complexes. Our work provides guidance for rational bimetallic design, suggesting that properties, including the formal shortness ratio, should be transferable from one period to another.

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1 Citations


Open accessJournal ArticleDOI: 10.1007/S11244-021-01480-7
Abstract: Recent advances in alkaline earth (Ae) metal hydrogenation catalysis have broadened the spectrum of potential catalysts to include candidates from the main group, providing a sustainable alternative to the commonly used transition metals. Although Ae-amides have already been demonstrated to catalyze hydrogenation of imines and alkenes, a lucid understanding of how different metal/ligand combinations influence the catalytic activity is yet to be established. In this article, we use linear scaling relationships and molecular volcano plots to assess the potential of the Ae metal-based catalysts for the hydrogenation of alkenes. By analyzing combinations of eight metals (mono-, bi-, tri-, and tetravalent) and seven ligands, we delineate the impact of metal-ligand interplay on the hydrogenation activity. Our findings highlight that the catalytic activity is majorly determined by the charge and the size of the metal ions. While bivalent Ae metal cations delicately regulate the binding and the release of the reactants and the products, respectively, providing the right balance for this reaction, ligands play only a minor role in determining their catalytic activity. We show how volcano plots can be utilized for the rapid screening of prospective Ae catalysts to establish a guideline to achieve maximum activity in facilitating the hydrogenation process.

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Topics: Catalysis (54%), Transition metal (51%)


Open accessJournal ArticleDOI: 10.1021/ACSCENTSCI.1C00535
Wendy L. Williams1, Wendy L. Williams2, Lingyu Zeng3, Tobias Gensch4  +4 moreInstitutions (5)
Abstract: Organic chemistry is replete with complex relationships: for example, how a reactant's structure relates to the resulting product formed; how reaction conditions relate to yield; how a catalyst's structure relates to enantioselectivity. Questions like these are at the foundation of understanding reactivity and developing novel and improved reactions. An approach to probing these questions that is both longstanding and contemporary is data-driven modeling. Here, we provide a synopsis of the history of data-driven modeling in organic chemistry and the terms used to describe these endeavors. We include a timeline of the steps that led to its current state. The case studies included highlight how, as a community, we have advanced physical organic chemistry tools with the aid of computers and data to augment the intuition of expert chemists and to facilitate the prediction of structure-activity and structure-property relationships.

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References
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54 results found


Journal ArticleDOI: 10.1021/JP047349J
Abstract: We present a method for calculating the stability of reaction intermediates of electrochemical processes on the basis of electronic structure calculations. We used that method in combination with detailed density functional calculations to develop a detailed description of the free-energy landscape of the electrochemical oxygen reduction reaction over Pt(111) as a function of applied bias. This allowed us to identify the origin of the overpotential found for this reaction. Adsorbed oxygen and hydroxyl are found to be very stable intermediates at potentials close to equilibrium, and the calculated rate constant for the activated proton/electron transfer to adsorbed oxygen or hydroxyl can account quantitatively for the observed kinetics. On the basis of a database of calculated oxygen and hydroxyl adsorption energies, the trends in the oxygen reduction rate for a large number of different transition and noble metals can be accounted for. Alternative reaction mechanisms involving proton/electron transfer to ...

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Topics: Overpotential (59%), Reaction rate constant (57%), Oxygen (53%) ... read more

5,473 Citations


Journal ArticleDOI: 10.1149/1.1856988
Abstract: Department of Physics, Technical University Munich, D-85748 Garching, GermanyA density functional theory database of hydrogen chemisorption energies on close packed surfaces of a number of transition andnoble metals is presented. The bond energies are used to understand the trends in the exchange current for hydrogen evolution. Avolcano curve is obtained when measured exchange currents are plotted as a function of the calculated hydrogen adsorptionenergies and a simple kinetic model is developed to understand the origin of the volcano. The volcano curve is also consistent withPt being the most efficient electrocatalyst for hydrogen evolution.© 2005 The Electrochemical Society. @DOI: 10.1149/1.1856988# All rights reserved.Manuscript submitted May 10, 2004; revised manuscript received August 12, 2004. Available electronically January 24, 2005.

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Topics: Hydrogen (51%)

2,623 Citations


Journal ArticleDOI: 10.1002/CCTC.201000397
11 Jul 2011-Chemcatchem
Abstract: Trends in electrocatalytic activity of the oxygen evolution reaction (OER) are investigated on the basis of a large database of HO* and HOO* adsorption energies on oxide surfaces. The theoretical overpotential was calculated by applying standard density functional theory in combination with the computational standard hydrogen electrode (SHE) model. We showed that by the discovery of a universal scaling relation between the adsorption energies of HOO* vs HO*, it is possible to analyze the reaction free energy diagrams of all the oxides in a general way. This gave rise to an activity volcano that was the same for a wide variety of oxide catalyst materials and a universal descriptor for the oxygen evolution activity, which suggests a fundamental limitation on the maximum oxygen evolution activity of planar oxide catalysts.

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Topics: Oxygen evolution (57%), Oxide (57%), Overpotential (53%) ... read more

2,154 Citations


Journal ArticleDOI: 10.1016/J.JELECHEM.2006.11.008
Jan Rossmeisl1, Z.-W. Qu2, H. Zhu2, Geert-Jan Kroes2  +1 moreInstitutions (2)
Abstract: In this paper, density functional theory (DFT) calculations are performed to analyze the electrochemical water-splitting process producing molecular oxygen (O 2 ) and hydrogen (H 2 ). We investigate the trends in the electro-catalytic properties of (1 1 0) surfaces of three rutile-type oxides (RuO 2 , IrO 2 , and TiO 2 ). The two first of these oxide anodes show lower O 2 -evolving over-potentials than metal anodes, due to weak O binding but strong hydroxyl (HO ∗ ) binding on the surface. Furthermore, the binding energies of O, HO, and HOO on the (1 1 0) surfaces fulfill universal linear relations similar to those found on metal surfaces.

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Topics: Oxide (54%), Binding energy (51%), Hydrogen (51%) ... read more

1,600 Citations


Journal ArticleDOI: 10.1016/S0022-0728(72)80485-6
Abstract: Summary The dependence of the exchange current for the electrolytic evolution of hydrogen on metals ( i 0,H ) on the work function () is analyzed on the basic of a new list offor polycrystalline surfaces. It is shown that log i 0,H is linearly related toirrespective of the detailed nature of the mechanism involved in the rate determining step (rds). i 0,H on sp metals depends on the sign of the surface charge. Results confirm previous suggestions that the main difference in double layer structure between sp and transition metals arises as a result of hindered rotation of water molecules on the latter. If the strength of the M−H bond is taken into consideration, then metals divide into two groups: (a) sp metals, with slow discharge at usual overvoltages, and probably slow hydrogen removal close to equilibrium, and (b) transition metals, with slow hydrogen removal as the rate determining step. Mn is anomalous and cannot be assigned to either class in correlations. Dependence of M−H bond strength onis also shown and discussed.

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Topics: Electronegativity (53%), Hydrogen (52%), Rate-determining step (51%)

1,230 Citations


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