Universality in Oxygen Reduction Electrocatalysis on Metal Surfaces

Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Rossmeisl, Jan; Nørskov, Jens K.

doi:10.1021/cs300227s

Cited by 491 publications

(552 citation statements)

References 32 publications

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“…Several studies have noted the presence or importance of intermediate species in reactions occurring in metal-oxygen batteries, 51,67 or in other contexts. 59,62,64,65 Finally, it is instructive to compare the present results for an Mg/O2 cell to studies on the Li/O2 system. [35][36][37]66,73 A recent report by Viswanathan et al 37 Table 2.…”

Section: Mgo2 (100) Stoichiometric Surfacementioning

confidence: 89%

Theoretical Limiting Potentials in Mg/O₂ Batteries

et al. 2016

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ABSTRACT:A rechargeable battery based on a multi-valent Mg/O2 couple is an attractive chemistry due to its high theoretical energy density and potential for low cost. Nevertheless, metal-air batteries based on alkaline earth anodes have received limited attention and generally exhibit modest performance. In addition, many fundamental aspects of this system remain poorly understood, such as the reaction mechanisms associated with discharge and charging. The present study aims to close this knowledge gap and thereby accelerate the development of Mg/O2 batteries by employing first-principles calculations to characterize electrochemical processes on the surfaces of likely discharge products, MgO and MgO2. Thermodynamic limiting potentials for charge and discharge are calculated for several scenarios, including variations in surface stoichiometry and the presence/absence of intermediate species in the reaction pathway. The calculations indicate that pathways involving oxygen intermediates are preferred, as they generally result in higher discharge and lower charging voltages. In agreement with recent experiments, cells that discharge to MgO exhibit low round-trip efficiencies, which are rationalized by the presence of large thermodynamic overvoltages. In contrast, MgO2-based cells are predicted to be much more efficient: superoxide-terminated facets on MgO2 crystallites enable low overvoltages and round-trip efficiencies approaching 90%. These data suggest that the performance of Mg/O2 batteries can be dramatically improved by biasing discharge towards the formation of MgO2 rather than MgO.

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Section: Mgo2 (100) Stoichiometric Surfacementioning

confidence: 89%

Theoretical Limiting Potentials in Mg/O₂ Batteries

et al. 2016

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“…We note that the above approach is valid for heterogeneous, homogeneous, and biological catalysis, and it has been used for electrochemical processes (17)(18)(19). We illustrate this strategy below for the case of a heterogeneous catalytic reaction as illustrated in Fig.…”

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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“…Experimentally, the ORR electrode activity follows a volcano-type correlation when it is plotted as function of the adsorption energy of oxygen atoms to 5 the catalyst surface, ΔG Oads , with the polycrystalline platinum catalyst close to the top [1,2]. Theoretically, calculations state that pure Pt has a slightly large ΔG Oads to be optimal and that the potential determining step in the ORR mechanism, related with the rate determining step (RDS) in some analysis [3][4][5], is the removal of adsorbed oxygen, O ads , or adsorbed hydroxide, OH ads , from the catalyst surface [3][4][5]. Following this idea, 10 catalysts with smaller ΔG Oads would have higher ORR activities than pure Pt, and this principle has been used by several groups as a foundational basis in designing new catalysts [9,10].…”

Section: Introductionmentioning

confidence: 99%

Oxygen reduction on nanostructured platinum surfaces in acidic media: Promoting effect of surface steps and ideal response of Pt(1 1 1)

Gómez–Marín

Feliu

2015

Catalysis Today

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Abstract:In this paper, the role of surface steps on the electrocatalytic activity of Platinum nano-10 structured surfaces for the oxygen reduction reaction (ORR) in acidic medium is evaluated by using stepped surfaces of structure Pt(S)[n(111)x (111)] with large terraces (20 ≤ n ≤ 50). It is realized that the inclusion of an even low amount of surface steps enhances the ORR, and linear activity trends are measured when currents at constant potential are plotted vs. the step density. As a consequence, an ideal ORR curve for a 15 defect-free Pt(111) surface is extrapolated at zero defect density from experimental data and can be compared to that of a quasi perfect Pt(111) electrode. It is clearly shown that surface steps promote the electrode activity toward ORR in acid medium. Results are discussed in light of available theoretical and experimental data.

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Universality in Oxygen Reduction Electrocatalysis on Metal Surfaces

Cited by 491 publications

References 32 publications

Theoretical Limiting Potentials in Mg/O₂ Batteries

Theoretical Limiting Potentials in Mg/O₂ Batteries

Analysis of reaction schemes using maximum rates of constituent steps

Oxygen reduction on nanostructured platinum surfaces in acidic media: Promoting effect of surface steps and ideal response of Pt(1 1 1)

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Universality in Oxygen Reduction Electrocatalysis on Metal Surfaces

Cited by 491 publications

References 32 publications

Theoretical Limiting Potentials in Mg/O2 Batteries

Theoretical Limiting Potentials in Mg/O2 Batteries

Analysis of reaction schemes using maximum rates of constituent steps

Oxygen reduction on nanostructured platinum surfaces in acidic media: Promoting effect of surface steps and ideal response of Pt(1 1 1)

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Product

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Theoretical Limiting Potentials in Mg/O₂ Batteries

Theoretical Limiting Potentials in Mg/O₂ Batteries