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Heterogeneous Molecular Catalysis of Electrochemical Reactions. Volcano Plots and Catalytic Tafel Plots Cyrille Costentin, and Jean-Michel Savéant ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 22 May 2017 Downloaded from http://pubs.acs.org on May 29, 2017
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ACS Applied Materials & Interfaces
Heterogeneous Molecular Catalysis of Electrochemical Reactions. Volcano Plots and Catalytic Tafel Plots Cyrille Costentin* and Jean-Michel Savéant* Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Université CNRS N° 7591, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France.
[email protected]*,
[email protected]* Keywords: Energy, Catalysis, Electrochemical reactions, Volcano plots, Catalytic Tafel plots, Cyclic Voltammetry the electrode surface molecules that have been proved to be efficient homogeneous molecular catalysts. ABSTRACT: We analyze here, in the framework of heterogeneous molecular catalysis the reasons of occurrence or non-occurrence of volcanoes upon plotting the kinetics of the catalytic reaction versus the stabilization free energy of the primary intermediate of the catalytic process. As in the case of homogeneous molecular catalysis or catalysis by surface active metallic sites, a strong motivation of such studies relates to modern energy challenges, particularly those involving small molecules such as water, hydrogen, oxygen, proton and carbon dioxide. This motivation is particularly pertinent for what concern heterogeneous molecular catalysis since it is commonly preferred to homogeneous molecular catalysis by the same molecules if only for chemical separation purposes and electrolytic cell architecture. As with the two other catalysis modes, the main drawback of the volcano plot approach is the basic the assumption that the kinetic responses depend on a single descriptor, viz., the stabilization free energy of the primary intermediate. More comprehensive approaches, investigating the responses to the maximal number of experimental factors, and conveniently expressed as catalytic Tafel plots, should clearly be preferred. This is the more so in the case of heterogeneous molecular catalysis that additional transport factors in the supporting film may additionally affect the current-potential responses. This is attested by the noteworthy presence of maxima in catalytic Tafel plots as well as their dependence upon the cyclic voltammetric scan rate.
Introduction A constantly increasing number of molecular systems, mostly transition metal complexes, are proposed for catalyzing electrochemical reactions, particularly oxidation or reduction of small molecules such as water, hydrogen, oxygen, proton and carbon dioxide, 1,2,3,4,5,6,7 in the framework of contemporary energy challenges. Although homogeneous molecular catalysis may be a quite valuable approach to this endeavor, films containing the same molecules deposited onto the electrode surface are likely to be preferred, if only for easing product separation. Another motivation is that such catalytic electrodes can be used in complete electrolytic cells, including appropriate counterelectrodes and separators taking advantage of existing technologies in the electrolyzer and fuel cell areas. We may thus expect a rapid development of this type of catalytic systems by immobilizing onto
Among the next tasks, one is the delineation of rational catalysts’ benchmarking procedures and the other is the quest of leading principles that could inspire the design of improved catalysts. In this venture, we can rely on the results of several preceding investigations. Dealing with catalyst’ benchmarking, it has been shown that it is efficiently operated by means of catalytic Tafel plots relating, for each system under examination, the turnover frequency to the overpotential. It remains to see how this approach introduced for homogeneous molecular catalysts can be transposed to deposited molecular catalysts. Concerning the second issue, analogy with catalysis of electrochemical reactions by surface-active sites, on the one hand and to homogeneous molecular catalysis on the other points to the idea that the stability of the intermediate formed in the initial phase of the reaction might be the main factor of catalytic efficiency. Increasing the stability of the intermediate should generate two contradictory effects. One is to favorably lower the energy barrier for the formation of the intermediate. The other is that a large stabilization of the intermediate will slow down its conversion into products and the ensuing regeneration of the catalytic surface. Application of this “Sabatier principle” 8 −thus predicts the existence of a maximum − a “volcano”− on the plot of the exchange current vs. the adsorption free energy of the intermediate within a family of electrocatalysts of a given reaction. These notions have been put forward as early as the late fifties,9,10 but are still the subject of active attention and debate at present time. 11,12,13,14 Their application to homogeneous molecular catalysis is quite recent, 15 and in the transposition to molecular film catalysis we have to take into account the various modes of the coupling between transport of reactants and charge and catalytic reactions. 16,17,18,19,20,21 In order to focus on the possible occurrence of volcano plots in the context of molecular film catalysis, we consider conditions in which the catalytic reaction is the rate-determining factor at the exclusion of charge and reactant transport (the film behaves as a monolayer or as a set of identically behaving monolayers). Within this framework, we will first analyze a simple molecular catalysis one-electron-one-step reaction scheme so as to get down to the nitty-gritty of the appearance or nonappearance of such volcano plots. Then, we will analyze two-steps mechanisms and discuss the role of relative stability of the intermediate. This will allow a critical evaluation of the pertinence of the volcano plot approach, leading to the examination of the catalytic Tafel plot alternative approach. Results and Discussion One-electron-one-step catalytic process. The reaction mechanism depicted in Scheme 1 for the electrochemical reduction of substrate A into product C corresponds to the fast (Nernstian) equilibrated electron transfer leading to the active form of the
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catalyst, Q, followed by the irreversible reaction of the substrate A present at the electrode surface with immobilized Q molecules, leading to the product C and regenerating the oxidized form of the catalyst, P (the reasonings and terminology are for reductions here and throughout the paper. They should be appropriately transposed for oxidations). As shown in the energy diagram of Scheme 1, the driving force of the
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the catalyst molecules that effectively participate to the catalytic reaction are contained in a thin reaction-diffusion layer, which is equivalent to the film that contains the immobilized catalyst molecules in the present case. The same data may also be reorganized under the form of catalytic Tafel plots, which relates the turnover frequency to the overpotential. For relating the rate constant of the catalytic reaction to its driving force we may use the classical linearized law of outersphere electron transfers, which introduces a driving force-independent transfer coefficient, α and k0 the standard rate constant of the reaction, i.e., the rate constant at zero driving force:
(
)
0 0 k = k 0 exp −α ( F / RT ) Ecat − EAC
(2)
From combination of equations (1) and (2), the turnover frequency may then be expressed by equation (3).
Scheme 1. One-electron-one-step reaction scheme. 0 0 being the overall process is the overpotential, η = EAC − E , E AC
standard potential of the A/C couple and E the electrode potential. In this scheme, there is no intermediate between the active form of the catalyst, Q, in its reaction with the substrate A, en route to the formation of the product C and the regeneration of the oxidized form of the catalyst, P. The only thermodynamic descriptor of this simple
(
with 0 < α < 1,
TOF k 0CA0
=
1 α F E 0 − E0 cat AC exp RT (α − 1) F E 0 − E 0 AC cat + exp − Fη × exp RT RT
(
)
(
)
0 0 reaction is its driving force, namely F E cat . Looking for − E AC
)
(3)
volcano plots in a similar manner as in electrocatalysis then amounts Figure 1 shows various ways of representing the TOF-overpotential to evaluate the electrochemical kinetic response as a function of correlation expressed by equation (3). The most classical one simply consists in plotting the catalytic rate constant or equivalently, the 0 0 . The most appropriate expression of the kinetics is F E cat − E AC maximal value of the TOF, TOFmax obtained for η → ∞ , against the the turnover frequency, TO F = N product / N cat , where N is product catalyst standard potential (figure 1a). the number of moles produced in a unit of time and N cat , the total
(
)
number of moles of catalyst. Since electron transfer in the catalyst couple is assumed to be fast, the Nernst law applies to the P/Q immobilized couple:
(
)
F 0 E − Ecat RT
Γ P = Γ Q exp
(the Γ s are the surface concentrations of the subscript species). The very fact that pure kinetic conditions have been assumed to hold implies that Q obeys the steady-state approximation. The relationship between the turnover frequency and the overpotential can therefore be Fig. 1. Reaction Scheme 1. a: variation of the catalytic rate constant expressed (see Supporting information (SI)) by equation (1). (or of TOFmax) with its driving force (α = 0.5); b: catalytic Tafel plots; c: volcano plots. Colored dots and curves are for 0 kC A (1) 0 0 TOF = -1 (blue), -2 (green), -3 (red), -4 (1 (magen− E AC ( F / RT ) Ecat F F 1 + exp − η exp − E0 − E0 cat AC RT RT ta), -5 (orange). c: black curves: from bottom to top ( F / RT )η = 1,
(
0
( CA : bulk concentrations of substrate).
(
)
)
2, 3, 4, 5.
The results reported in figure 1b may be reorganized as catalytic Tafel Equation (1) shows that the kinetic response is a trade-off between the plots, which relates the turnover frequency to the overpotential 0 0 equilibrated formation of Q through: exp ( F / RT )( EAC − Ecat ) and η = E0 − E for a series of values of the catalyst standard potential AC
(
)
0 the kinetics of the chemical step through kCA .
(figure 1b). As compared to figure 1a, there is no additional information besides the fact that electrode electron transfer in the catalyst It is noteworthy that equation (1) is exactly the same as in homogene- couple is assumed to be fast enough to obey the Nernst law. However, ous molecular catalysis. 15 The reason for this is that, in the latter case, introduction of the electrode potential, E, through the overpotential,
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allows the selection of appropriate conditions for establishing the desired compromise between energy expense and rate of substrate conversion. Comparison between catalytic Tafel plots thus offers a straightforward means of benchmarking catalysts both in terms of overpotential and turnover frequency. Noteworthy in this respect is the possible crossing of catalytic Tafel plots, indicating that a given catalyst may have a better TOF than another one at a given overpotential while the order may be reversed at another overpotential. This observation directly leads to the third representation shown in figure 1c where the TOF is plotted against the catalyst standard potential, that shows maxima (volcanoes) in the zones where the catalytic Tafel plots cross each other.
tial,
0 η = EAC −E
and
the
same
the
turnover
frequency,
TOF = N product / N cat , as in the preceding section, using the same
definitions as when the catalytic Tafel plots, relating TOF to η were first introduced. 22,23 The search of volcanoes thus consists, as in the homogeneous case, 15 in plotting the catalysis kinetics, represented by the TOF, against the stabilization of the intermediates, expressed as
(
)
0 0 the standard free energy of reaction (1)+(2), F E cat , for − E AC
selected values of the overpotential. We may, alternatively, represent the kinetics of the global reaction by drawing, for each catalyst, the above-defined catalytic Tafel plot. The variation of the electrode In closing this section, we thus emphasize that the observation of potential, E, which is in the catalytic Tafel plot expression, merely volcano plots offers nothing extraordinary since it may occur with a induces a variation of the concentration ratio between oxidized and catalytic mechanism as simple as the one depicted in Scheme 1. reduced form of the catalyst leading to a variation of the catalytic current. In most cases, electron transfer is fast, justifying the applicaOne-electron-two-step catalytic processes. bility of the Nernst law, which relates the concentration ratio Γ / Γ , P Q We now consider the one-electron-two-step reaction depicted in Scheme 2 under two possible kinetic regimes. In the (Rev-S) regime, to the electrode potential and to the standard potential of the catalyst the 1st step is reversible, the 2nd step is irreversible and the intermedi0 couple, Ecat according to: ate B is at steady-state. In the (Irr-nS) regime, the 1st and 2nd steps are irreversible and the intermediate B is not necessarily at steady-state, Γ P = exp F E − E 0 = exp Fη exp − F E 0 − E 0 meaning that it may accumulate. The thermodynamics of the global RT RT cat cat AC ΓQ RT
(
)
(
)
The TOF is also a function of the kinetics of each of the two steps. We assume that the respective rate constants are related to the corresponding driving forces in a linear manner, by means of the driving forceindependent transfer coefficients, α1 and α2:
(
)
1 − α ∆G 0 α ∆G 0 1 1 k1C 0 = k10 exp − 1 1 , k−1 = k10 exp RT RT
α ∆G 0 k2 = k20 exp − 2 2 RT
k10 and k 20 are the rate constants at zero driving force, C 0 a normalizing concentration. As indicated earlier, we consider that within a series of catalysts, a scaling relationship links the relative stability of the intermediates so that: Scheme 2. One-electron-two-step reaction schemes. reaction and of the various steps of the catalytic process is governed
∆G10 F
(
)
0 0 = β1 E cat − E AC + C1 and
∆ G 20 F
(
)
0 0 = (1 − β 1 ) E cat − E AC − C1
0 0 and E cat and by the standard free with a constant proportionality coefficients, β and a constant value of by the standard potentials E AC 1 energies of step 1 and 2, ∆ G10 and ∆ G 20 , respectively. Unlike the C1 within the family.
case of surface-active sites catalyzed electrochemical reactions, as well as the preceding one-electron-one-step molecular process, with only one intermediate, the mechanistic scheme considered here involves two intermediates, namely Q and B. However, we consider the case where a scaling relationship links the relative stability of both intermediates, within a series of catalysts, so that, if any, the volcano plots should appear upon plotting the electrochemical kinetic response as a function of F
(
0 E cat
−
0 E AC
) . We introduce the same overpoten-
Experimental examples of such behaviors have been recently reported for the catalysis of CO2 and O2 reductions by the FeI/0 and FeIII/II couples of diversely substituted iron porphyrins in the homogeneous case. 24,25 We can thus introduce k * and k * as the rate constants of the two 1 2 0 0 steps, not at zero driving force, but for Ecat − EAC = 0. Then:
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k1 k1*
Figure 2 illustrates some examples of TOFmax-driving force plots, catalytic Tafel plots and volcano plots characteristics of the (Rev-S) regime as results from the application of equation (2).
FC1 α βF * 0 0 0 = exp − 1 1 Ecat − E AC with k1 = k1 exp −α1 RT RT
(
(
)
)
1−α β F 1 1 0 0 − = − EAC exp Ecat RT k−*1 k−1
(
(
)
α 1− β F 1 0 0 − 2 = − EAC exp Ecat RT k2* k2
(
)
)
FC1 , k* = k0 exp − 1 − α − 1 1 1 RT
(
We note that the occurrence of volcanoes in plotting the TOF response vs. the stability of the primary intermediate is closely related to crossings of catalytic Tafel plots. We also see that the appearance or non-appearance of volcanoes strongly depends on the value of the overpotential at which the TOF is recorded. This is one consequence of the oversimplification introduced by the assumption that the reaction kinetics is depending upon a single, descriptor, viz., the free energy of stabilization of the primary intermediate. Several other parameters are likely to come
)
with: k * = k 0 exp α FC1 2 2 2 RT
There are thus four kinetic parameters k *C 0 , k * and α1 and α 2 1 2
. Normalizing TOF vs
k1*C 0
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or k * leads to only three kinetic parame2
ters that we will also considered as constant within the family of catalysts.
- The (Rev-S) regime The validity of the steady-state approximation on B allows the derivation of a closed-form expression of TOF (η ) . Indeed (see SI):
k1k2CA0 TOF =
i FS Γ P0
k−1 + k2
= 1+
k1CA0
( k−1 + k2 )
(
)
F 0 E − Ecat + exp RT .
0 where i is the current, S the electrode surface area and Γ the total Fig. 2. Reaction Scheme 2, (Rev-S) regime. a: variation of TOFmax P 0 A
surface concentration of catalyst present on the electrode surface. C
with the catalytic reaction driving force; b: catalytic Tafel plots; c:
* * 0 volcano plots. k2 / k1 CA = 1 , β1 = 1 , α1 = α2 = 0.5. Colored dots
is the concentration of substrate assumed to be the same throughout the solution. With the same definition of TO F = N product / N cat as and curves are for
( F / RT )
0 ( Ecat0 − EAC ) : -1 (blue), -2 (green), -3
before and taking into account the above-mentioned scaling relation- (red), -4 (1 (magenta), -5 (orange). c: black curves: from bottom to top ( F / RT )η = 1, 2, 3, 4, 5. ship:
) (
(
)
α 1 − β F E0 − E0 cat 2 1 AC = exp − × * RT k2 β F E0 − E0 0 CA cat 1 AC exp − 0 RT C 0 0 − EAC F Ecat k* 1 + * 2 0 exp − 1 − α1 β1 − α 2 1 − β1 RT k1 C 0 0 0 F E − E β CA 1 cat AC exp − RT C0 + 1 0 0 F Ecat − EAC 1 + exp − 1 − α1 β1 − α 2 1 − β1 RT 0 0 F Ecat − EAC F + + exp − η RT RT
TOF
(
(
)
)
(
(
)
(
(
)
(
into play (see the list of parameters in the caption of figure 1), to which other values could have been assigning with, as consequence, diverse apparitions of the volcanoes. It consequently appears that the expression of the experimental data under the form of catalytic Tafel plot offers a much less restricted picture of the kinetics of catalysis.
)
)
(
)
)
(
)
(4)
It is again worth noting that equation (2) and figure 2 are exactly the same as their counterpart in homogeneous molecular catalysis. 15 The reason for this is, as for Scheme 1, that, in the homogeneous case, the catalyst molecules that effectively participate to the catalytic reaction are squeezed into a thin reaction-diffusion layer equivalent to the film that contains the immobilized catalyst molecules in the present case.
- The (Irr-nS) regime Unlike the previous one, this regime is expected to give rise to behaviors that largely differ when passing from homogeneous to heterogeneous molecular catalysis. The non-stationarity of the intermediate B takes indeed place in quite different conditions in the two cases. In the homogeneous case, an overall steady state is eventually established by the fact that B diffusion comes into play besides the reactions that generate and consume B. This does not happens in the heterogeneous case, where non-stationary behaviors should manifest
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themselves as a time-dependency of the responses which results in a the overpotential, also meaning large times, entails that the concentrascan rate dependency in the framework of cyclic voltammetry. The tions of B and Q have reached a steady state to which corresponds a turnover frequency depends on thermodynamics parameters limiting current and thereof a limiting value of the turnover frequency 0 (see SI): 0 0 0 Ecat −EAC ,β , α , α and kinetics parameters k2* / k1*CA , RTk C / ( Fv) 1 1 2 1 A 0 0 − EAC β F Ecat TOFη =∞ and can only be computed numerically as described in the SI. −α 1 × = exp 1 RT Examples of catalytic Tafel plots and volcano plots computed in k1*C A0 this way are represented in figure 3 for a fixed value of the scan-rate 0 0 − EAC F Ecat 0 k2* α β −α 1− β dependent parameter, RTk1CA / ( Fv) as well as the others kinetics (5) exp 2 1 * 0 1 1 RT k C 0 0 1 A and thermodynamics parameters except ( E cat − E AC ) . We note, as in 0 0 * F Ecat − EAC the other cases, the occurrence of more or less marked volcanoes on k 1 + * 2 0 exp α1β1 − α 2 1 − β1 0 0 RT the TOF - E cat plots. k1 CA − E AC
(
)
(
)
(
(
))
(
(
)
(
)
))
(
(
)
(
)
TOFη =∞ is an increasing function of the stabilization of the primary
(
)
0 0 intermediate, measured by - Ecat . − EAC
All curves in figures 3a tend toward the limit expressed by equation (4), more or less rapidly according the value of the parameter 0 RTk1CA / ( Fv) . In the case of figure 3c, this limit is the same for all curves in spite of a largely different pace (depending on 0 RTk1CA / ( Fv) ) to reach it. From the starting potential, where it is nil to its long-time steady value, the concentration of B and hence the TOF goes through a maximum as pictured in figure 3c (see SI for more details). We again see that the occurrence or non-occurrence of volcano plots considerably depend on the values of the governing parameters.
Conclusion
Fig. 3. Reaction Scheme 1, (Irr-nS) regime. Catalytic Tafel plots (left) * * 0 and volcano plots (right) for k2 / k1 CA = 1 , β1 = 1 , α1 = α2 = 0.5. a,
0 b: RTk1CA / ( Fv )
= 1, Dots and curves are for
(F
/ RT
)
0 ( Ecat0 − EAC ) = 0 (blue), -1 (green), -2 (red), -3 (magenta), -4 (or-
ange). b: from bottom to top:
( F / RT )η
= 0, 1, 2, 3, 4. c, d:
0 RTk1CA / ( Fv) = 0.05 (green), 0.1 (red), 1 (orange), ≥ 2 (blue). 0 0 − E AC ( F / RT ) ( E cat )
= -4 . d: ( F / RT )η = 1.
A striking quite unusual feature of the catalytic Tafel plots (TOF – η) drawn in the same conditions is that they show a maximum and that they are dependent on the scan rate (v) through the dimensionless 0 parameter, RTk1CA / ( Fv ) . The TOF – η are derived from the
In heterogeneous molecular catalysis, as in the case of homogeneous molecular catalysis or catalysis by surface active metallic sites, the occurrence or non-occurrence of volcanoes upon relating the catalytic kinetics to the stabilization free energy of the initial intermediate depend on a number of additional parameter. This observation emphasizes the main drawback of the volcano plot approach, namely, the assumption that the kinetic responses may depend with a good approximation on a single descriptor, viz., the stabilization free energy of the primary intermediate. More comprehensive approaches, investigating the responses to the maximal number of experimental factors, and conveniently expressed as catalytic Tafel plots, should clearly be preferred. This is the more so in the case of molecular catalysis in films, that additional transport factors may affect the current-potential responses in addition to those we have taken into account in our analysis.
ASSOCIATED CONTENT Supporting Information Available: Derivation of equations (1) - (3). This material is available free of charge via the Internet at http://pubs.acs.org. REFERENCES
cyclic voltammetric responses in which the electrode potential is scanned linearly with time. The behavior observed at large values of
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1. Hoffert, M. I.; Caldeira, K.; Jain, A. K.; Haites, E. F.; Harvey, L. D. D.; Potter, S. D.; Schlesinger, M. E.; Schneider, S. H.; Watts, R. G.; Wigley, T. M. L.; Wuebbles, D. J.: Energy Implications of Future Stabilization of Atmospheric CO2 Content. Nature 1998, 395, 881-884. 2. Lewis, N. S.; Nocera, D. G.: Powering The Planet: Chemical Challenges in Solar Energy Utilization. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 15729-15735. 3. Gray, H. B.: Powering the Planet with Solar Fuel. Nat Chem 2009, 1, 77. 4. Nocera, D. G.: Chemistry of Personalized Solar Energy. Inorg. Chem. 2009, 48, 10001-10017. 5. Abbott, D.: Keeping the Energy Debate Clean: How Do We Supply the World's Energy Needs? Proceedings of the IEEE 2010, 98, 42-66 6. Chu, S.; Majumdar, A.: Opportunities and Challenges for a Sustainable Energy Future. Nature 2012, 488, 294-303. 7. Artero, V.; Fontecave, M.: Solar Fuels Generation and Molecular Systems: Is It Homogeneous or Heterogeneous Catalysis? Chem. Soc. Rev. 2013, 42, 2338-2356. 8. Sabatier, P., La Catalyse En Chimie Organique, Librairie Polytechnique, Paris et Liège, 1920. 9. Parsons, R., the Rate of Electrolytic Hydrogen Evolution and the Heat of Adsorption of Hydrogen. T. Faraday Soc. 1958, 54, 1053-1063. 10. Gerischer, H., Mechanismus Der Elektrolytischen Wasserstoffabscheidung Und Adsorptionsenergie von Atomarem Wasserstoff. Bulletin des Sociétés Chimiques Belges 1958, 67, 506-527. 11. Koper, M. T. M., Analysis of Electrocatalytic Reaction Schemes: Distinction between Rate-Determining and Potential-Determining Steps. Journal of Solid State Electrochemistry 2013, 17, 339-344. 12. Quaino, P.; Juarez, F.; Santos, E.; Schmickler, W., Volcano Plots in Hydrogen Electrocatalysis – Uses and Abuses. Beilstein Journal of Nanotechnology 2014, 5, 846-854. 13. Zeradjanin, A. R.; Grote, J.-P.; Polymeros, G.; Mayrhofer, K. J. J.: A Critical Review on Hydrogen Evolution Electrocatalysis: Re-exploring the Volcano-relationship. Electroanalysis 2016, 28, 2256-2269 14 . Costentin, C.; Saveant, J.-M. Catalysis of Electrochemical Reactions by Surface-Active Sites. Analyzing the Occurrence and Significance of Volcano Plots by Cyclic Voltammetry, submitted. 15. Costentin, C.; Saveant, J.-M. Molecular Catalysis of Electrochemical Reactions. Catalyst Benchmarking and Optimization Strategies, submitted. 16. Andrieux, C. P.; Savéant, J.-M.: Catalysis at Redox Polymer Coated Electrodes. In Molecular Design of Electrode Surfaces; Murray, R. W., Ed.; John Wiley & Sons: New York, NY, 1992; Vol. 22; pp 207-270. 17. Amarasinghe, S.; Ta-Yung, C.; Moberg, P.; Paul, H. J.; Tinoco, F.; Zook, L. A.; Leddy, J.: Models for Mediated Reactions at Film Modified Electrodes: Controlled Electrode Potential. Anal. Chim. Acta 1995, 307, 227-244. 18. Costentin, C.; Savéant, J.-M.: Cyclic Voltammetry of Electrocatalytic Films: Fast Catalysis Regimes. ChemElectroChem 2015, 2, 1774-1784. 19. Costentin, C.; Saveant, J.-M.: Cyclic Voltammetry of Fast Conducting Electrocatalytic Films. Phys. Chem. Chem. Phys. 2015, 17, 19350-19359. 20. Costentin, C.; Savéant, J.-M.: Cyclic Voltammetry Analysis of Electrocatalytic Films. J. Phys. Chem. C 2015, 119, 12174-12182. 21 Andrieux, C. P.; Costentin, C.; Di Giovanni, C.; Savéant, J.-M.; Tard, C.: Conductive Mesoporous Catalytic Films. Current Distortion and Performance Degradation by Dual-Phase Ohmic Drop Effects. Analysis and Remedies. J. Phys. Chem. C 2016, 120, 21263-21271. 22. Costentin, C.; Drouet, S.; Robert, M.; Saveant, J.-M.: Turnover Numbers, Turnover Frequencies and Overpotential in Molecular Catalysis of Electrochemical Reactions. Cyclic Voltammetry and Preparative-Scale Electrolysis. J. Am. Chem. Soc. 2012, 134, 11235-11242 23. Costentin, C.; Passard, G.; Savéant, J.-M.: Benchmarking of Homogeneous Electrocatalysts. Overpotential, Turnover Frequency, Limiting Turnover Number. J. Am. Chem. Soc. 2015, 137, 5461-5467. 24. Azcarate, I.; Costentin, C.; Robert, M.; Savéant, J.-M.: Dissection of Electronic Substituent Effects in Multielectron–Multistep Molecular Catalysis. Electrochemical CO2-to-CO Conversion Catalyzed by Iron Porphyrins. J. Phys. Chem. C 2016, 120, 28951-28960.
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25. Pegis, M. L.; McKeown, B. A.; Kumar, N.; Lang, K.; Wasylenko, D. J.; Zhang, X. P.; Raugei, S.; Mayer, J. M.: Homogenous Electrocatalytic Oxygen Reduction Rates Correlate with Reaction Overpotential in Acidic Organic Solutions. ACS Central Science 2016, 2, 850-856.
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