Reactivity Theory of Transition-Metal Surfaces: A Brønsted−Evans−Polanyi Linear Activation Energy−Free-Energy Analysis

Santen, Rutger A. van; Neurock, Matthew; Shetty, SG Sharankumar

doi:10.1021/cr9001808

Cited by 537 publications

(514 citation statements)

References 129 publications

(293 reference statements)

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“…The next step in the analysis is to estimate values for the activation barriers for all steps in the reaction scheme. For example, the activation barrier for a step could be estimated from an experimental value for the reaction of interest or a similar reaction, estimated from results of DFT calculations (37), or estimated using Brønsted-Evans-Polanyi (BEP) scaling relations (38)(39)(40). These BEP relations provide estimates for the thermodynamic properties of transition states in terms of stable adsorbed species, thereby allowing the estimation of activation energies in terms of the binding energies used above to determine the surface coverages by adsorbed species.…”

Section: Analytical Strategy For Analysis Of Reaction Schemesmentioning

confidence: 99%

Analysis of reaction schemes using maximum rates of constituent steps

Motagamwala

Dumesic

2016

Proc. Natl. Acad. Sci. U.S.A.

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We show that the steady-state kinetics of a chemical reaction can be analyzed analytically in terms of proposed reaction schemes composed of series of steps with stoichiometric numbers equal to unity by calculating the maximum rates of the constituent steps, r max,i , assuming that all of the remaining steps are quasi-equilibrated. Analytical expressions can be derived in terms of r max,i to calculate degrees of rate control for each step to determine the extent to which each step controls the rate of the overall stoichiometric reaction. The values of r max,i can be used to predict the rate of the overall stoichiometric reaction, making it possible to estimate the observed reaction kinetics. This approach can be used for catalytic reactions to identify transition states and adsorbed species that are important in controlling catalyst performance, such that detailed calculations using electronic structure calculations (e.g., density functional theory) can be carried out for these species, whereas more approximate methods (e.g., scaling relations) are used for the remaining species. This approach to assess the feasibility of proposed reaction schemes is exact for reaction schemes where the stoichiometric coefficients of the constituent steps are equal to unity and the most abundant adsorbed species are in quasi-equilibrium with the gas phase and can be used in an approximate manner to probe the performance of more general reaction schemes, followed by more detailed analyses using full microkinetic models to determine the surface coverages by adsorbed species and the degrees of rate control of the elementary steps.chemical kinetics | catalysis | microkinetics C hemical reactions take place through sequences of elementary steps, and the dynamics of the overall stoichiometric reaction are typically controlled by key steps in this sequence of steps. For example, in the case of a catalytic reaction, the reaction kinetics are controlled by the energetics of the transition states for the rate-controlling steps and by the energetics of species that are abundant on the active sites (i.e., the Gibbs free energies of these transition states and adsorbed species relative to the reactants and products of the overall stoichiometric reaction). However, whereas the observed reaction kinetics are controlled by a limited number of transition states and adsorbed species, it is typically required to carry out detailed microkinetic analyses to identify the nature of these key transition states and adsorbed species. Thus, a general strategy to elucidate how the reaction kinetics are controlled by a proposed reaction mechanism is first to carry out density functional theory (DFT) calculations to determine the thermodynamic properties of all adsorbed species and transition states, and then to build a microkinetic model to determine the surface coverages by all adsorbed species and the forward and reverse rates of all elementary steps for a range of reaction conditions (1-5). Sensitivity analyses are then carried out using this microkineti...

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Section: Analytical Strategy For Analysis Of Reaction Schemesmentioning

confidence: 99%

Analysis of reaction schemes using maximum rates of constituent steps

Motagamwala

Dumesic

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…16,17 Starting from this early proposal, several alternative formulations that end up correlating with a single adsorption energy have been derived. [18][19][20][21][22][23] In particular, the transition state scaling (TSS) relationships correlate the transition state energy with the energy of the initial or the final state of the reaction.…”

Section: Introductionmentioning

confidence: 99%

Descriptor Analysis in Methanol Conversion on Doped CeO₂(111): Guidelines for Selectivity Tuning

Capdevila‐Cortada

López

2015

ACS Catal.

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ABSTRACT:Descriptors are crucial to systematize and optimize activity, selectivity, and stability of catalysts. Adsorption energies have usually been taken as the main representative parameter that can summarize reaction energies and activation barriers for simple reactions on relatively simple reaction sites. However, more chemically sound terms, which can be directly mapped to experiments, would be more desirable.Besides, larger molecules with more than one potentially active position and complex sites, like the acid-base pairs present in oxides, are typically beyond the scope provided by common linear-scaling methods. In the present work, we have analyzed the selectivity of the conversion of a polyfunctional molecule on a complex oxide that presents both acid-base and redox chemistry. The conversion of methanol to formaldehyde or CO on isovalently doped ceria (111) has been taken as an example.The selectivity towards CO is triggered by the competition between formaldehyde desorption and C-H cleavage. Our results show that, by introducing dopant cations, the activation energy of the first H-stripping of formaldehyde can be decreased so that its conversion becomes favorable over desorption for Zr, Hf doped systems and expanded lattice ceria. More importantly, desorption is controlled by geometric and acid-base factors, whereas C-H cleavage is exclusively electronically governed through acid-base and redox factors. Thus, both geometric and electronic structure parameters are needed to optimize the performance of ceria to attain the desired selectivity. Selectivity is then estimated by a collective descriptor of the surface that incorporates the ensemble size, acid-base, and redox contributions that can be directly compared to experimental values. In addition, this scaling relationship reduces the error associated to more traditional energy-based descriptors. We can anticipate that the present scheme can be extended to metal oxides and other polyfunctionalized catalysts.2

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“…The structure sensitive reactions related to the above mentioned reactions viz F-T, TWC and H-B processes are the CO, NO and N 2 activation respectively. These reactions are not only structure-sensitive but are also considered to be the initial steps in the reaction sequences [14]. Hence, an appropriate active site for a low barrier activation of these diatomic molecules on the transition metal (TM) surfaces and nanoparticles is an important issue in the field of heterogeneous catalysis.…”

Section: Introductionmentioning

confidence: 99%

Site Structure Sensitivity Differences for Dissociation of Diatomic Molecules

Shetty

Santen

2010

Top Catal

Self Cite

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A review on the analysis based on our recent theoretical results on the site specific activation of CO, N 2 and NO on corrugated Ru surface is presented. We discuss the issues such as what should be the configuration of the active site for the optimum dissociation of the diatomic molecules?, How is the barrier dependent on the structure of the reaction path?, Whether the further steps involved in the reaction sequence dependent on the activation of the diatomic molecules?

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Reactivity Theory of Transition-Metal Surfaces: A Brønsted−Evans−Polanyi Linear Activation Energy−Free-Energy Analysis

Cited by 537 publications

References 129 publications

Analysis of reaction schemes using maximum rates of constituent steps

Analysis of reaction schemes using maximum rates of constituent steps

Descriptor Analysis in Methanol Conversion on Doped CeO₂(111): Guidelines for Selectivity Tuning

Site Structure Sensitivity Differences for Dissociation of Diatomic Molecules

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Reactivity Theory of Transition-Metal Surfaces: A Brønsted−Evans−Polanyi Linear Activation Energy−Free-Energy Analysis

Cited by 537 publications

References 129 publications

Analysis of reaction schemes using maximum rates of constituent steps

Analysis of reaction schemes using maximum rates of constituent steps

Descriptor Analysis in Methanol Conversion on Doped CeO2(111): Guidelines for Selectivity Tuning

Site Structure Sensitivity Differences for Dissociation of Diatomic Molecules

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Product

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Descriptor Analysis in Methanol Conversion on Doped CeO₂(111): Guidelines for Selectivity Tuning