Theory of the transition from sequential to concerted electrochemical proton–electron transfer

Koper, Marc T. M.

doi:10.1039/c2cp42369c

Cited by 102 publications

(109 citation statements)

References 61 publications

(103 reference statements)

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“…The simple kinetic modeling theory presented here builds on previous Hamiltonian modeling [28] and thermodynamic considerations [10]. The modeling confirms the role of pH in optimizing the reactivity of electrocatalytic reactions, leading to volcano-type activity relations if acid-base equilibria are involved in the reaction mechanism.…”

Section: Resultsmentioning

confidence: 88%

Volcano Activity Relationships for Proton-Coupled Electron Transfer Reactions in Electrocatalysis

Koper

2015

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This paper studies simple kinetic models for proton-coupled electron transfer reactions, and demonstrates that for reactions in which proton and electron do not transfer simultaneously, pH dependence of the overall reaction rate is expected. In particular, if the current is evaluated on the reversible hydrogen scale, this may lead to volcano-type activity relations as a function of pH. In case that an acid-base equilibrium is part of the mechanism, the optimal pH occurs close to the pK a of this equilibrium.

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Section: Resultsmentioning

confidence: 88%

Volcano Activity Relationships for Proton-Coupled Electron Transfer Reactions in Electrocatalysis

Koper

2015

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“…[16][17][18] It is important to elucidate those ORR processes at the atomic level, which may help to identify the rate-determining step of the ORR kinetics and the origin of the overpotential. Early work has suggested as equential reduction of oxygen on various electrode surfaces.…”

Section: Orr Mechanismsmentioning

confidence: 99%

Earth‐Abundant Nanomaterials for Oxygen Reduction

et al. 2015

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Replacing the rare and precious platinum (Pt) electrocatalysts with earth-abundant materials for promoting the oxygen reduction reaction (ORR) at the cathode of fuel cells is of great interest in developing high-performance sustainable energy devices. However, the challenging issues associated with non-Pt materials are still their low intrinsic catalytic activity, limited active sites, and the poor mass transport properties. Recent advances in material sciences and nanotechnology enable rational design of new earth-abundant materials with optimized composition and fine nanostructure, providing new opportunities for enhancing ORR performance at the molecular level. This Review highlights recent breakthroughs in engineering nanocatalysts based on the earth-abundant materials for boosting ORR.

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“…8). A theoretical thermodynamic argument has shown that this is a generic feature of sequential proton-electron transfer reactions (AH A − + H + followed by A [36][37][38]. Therefore, the pK a of the molecule of interest is an important factor for predicting the optimal pH for its oxidation.…”

Section: Kinetic Modeling Of Hcooh/hcoo − Oxidationmentioning

confidence: 99%

“…The significance of the present study goes beyond this relatively simple electrocatalytic system because many electrocatalytic reactions are strongly pH dependent and the pH dependence must be related to the decoupling of proton and electron transfer at some stage in the reaction mechanism [36][37][38]. Recently, such an effect was shown to be important for predicting the optimal pH for electrooxidation of alcohols on gold electrodes [39].…”

Section: Introductionmentioning

confidence: 99%

The effect of pH on the electrocatalytic oxidation of formic acid/formate on platinum: A mechanistic study by surface-enhanced infrared spectroscopy coupled with cyclic voltammetry

Joo

Uchida

Cuesta

et al. 2014

Electrochimica Acta

132

127

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Please cite this article as: J. Joo, T. Uchida, A. Cuesta, M.T.M. Koper, M. Osawa , The effect of pH on the electrocatalytic oxidation of formic acid/formate on platinum: A mechanistic study by surface-enhanced infrared spectroscopy coupled with cyclic voltammetry, Electrochimica Acta (2014), http://dx.doi.org/10. 1016/j.electacta.2014.02.040 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe electrocatalytic oxidation of formic acid (HCOOH) and formate (HCOO − ) to CO 2 on platinum has been studied over a wide range of pH (0-12) by surface-enhanced infrared absorption spectroscopy (SEIRAS) coupled with cyclic voltammetry. The peak current of HCOOH/HCOO − oxidation exhibits a volcano-shaped pH dependence peaked at a pH close to the pK a of HCOOH (3.75). The experimental result is reasonably explained by a simple kinetic model that HCOO − oxidation is the dominant reaction route over the whole pH range.HCOOH is oxidized after being converted to HCOO − via the acid-base equilibrium. The ascending part of the volcano plot at pH < 4 is ascribed mostly to the increase of the molar ratio of HCOO − , while the descending part at pH > 4 is ascribed to the suppression of HCOO − oxidation by adsorbed OH or oxidation of the electrode surface. In acidic media, HCOOH is

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Theory of the transition from sequential to concerted electrochemical proton–electron transfer

Cited by 102 publications

References 61 publications

Volcano Activity Relationships for Proton-Coupled Electron Transfer Reactions in Electrocatalysis

Volcano Activity Relationships for Proton-Coupled Electron Transfer Reactions in Electrocatalysis

Earth‐Abundant Nanomaterials for Oxygen Reduction

The effect of pH on the electrocatalytic oxidation of formic acid/formate on platinum: A mechanistic study by surface-enhanced infrared spectroscopy coupled with cyclic voltammetry

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