A theory of overpotential

Heyrovský, J.

doi:10.1002/recl.19270460805

Cited by 116 publications

(63 citation statements)

References 10 publications

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“…In addition, both these pathways could include a Tafel-type mechanism [33] where the solvated protons from the solution rst adsorb on the surface and combine with electrons and then the hydrogen adatoms react with adsorbed N 2 H x or NH x species. The other possible reaction mechanism is a Heyrovsky-type reaction [34] where the adsorbed N 2 H x or NH x species are hydrogenated by direct attachment of protons from the solution and electrons from the electrode. In the latter case an applied bias can directly aect the thermochemical barrier, whereas in the Tafel-type reaction it can only have an indirect eect through varying the concentrations of the reactants [35,36].…”

Section: Electrochemical Reactionsmentioning

confidence: 99%

A theoretical evaluation of possible transition metal electro-catalysts for N₂reduction

Skúlason

Bligaard

Guðmundsdóttir

et al. 2012

Phys. Chem. Chem. Phys.

1,299

1,468

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Theoretical studies of the possibility of forming ammonia electrochemically at ambient temperature and pressure are presented. Density functional theory calculations were used in combination with the computational standard hydrogen electrode to calculate the free energy prole for the reduction of N 2 admolecules and N adatoms on several close-packed and stepped transition metal surfaces in contact with an acidic electrolyte. Trends in the catalytic activity were calculated for a range of transition metal surfaces and applied potentials under the assumption that the activation energy barrier scales with the free energy dierence in each elementary step. The most active surfaces, on top of the volcano diagrams, are Mo, Fe, Rh, and Ru, but hydrogen gas formation will be a competing reaction reducing the faradaic eciency for ammonia production. Since the early transition metal surfaces, such as Sc, Y, Ti, and Zr bind N-adatoms more strongly than H-adatoms, a signicant production of ammonia compared with hydrogen gas can be expected on those metal electrodes when a bias of -1 V to -1.5 V vs. SHE is applied. Defect-free surfaces of the early transition metals are catalytically more active than their stepped counterparts.

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Section: Electrochemical Reactionsmentioning

confidence: 99%

A theoretical evaluation of possible transition metal electro-catalysts for N₂reduction

Skúlason

Bligaard

Guðmundsdóttir

et al. 2012

Phys. Chem. Chem. Phys.

1,299

1,468

View full text Add to dashboard Cite

show abstract

“…Among other applications of impedance to the stability analysis of electrochemical systems, one should note theoretical paper by Berthier et al [68] who described the multisteady I-E curves for the Volmer-Heyrovsky mechanism, which in classical electrochemistry has been used to explain the evolution of hydrogen [69] and chlorine [70], including the hydrogen evolution associated with iron electrodeposition [71]. For the oxidation reaction this mechanism consists of the following steps: Reprinted from [67], Copyright 1999, with permission from Elsevier…”

Section: The Volmer-heyrovský Mechanismmentioning

confidence: 99%

Application of Impedance Spectroscopy to Electrochemical Instabilities

Orlik

2012

Monographs in Electrochemistry

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Electrochemical impedance spectroscopy (EIS), a well-established technique in classical electrochemistry [1], can also be very useful for the analysis of stability of electrochemical systems, including diagnosis of selected bifurcations. Impedance spectra of such dynamical systems allow also classify electrochemical oscillators into respective types. In fact, due to linearization involved in the concept of impedance, this way of the stability analysis of electric (electrochemical) circuits is a specific variant of linear stability analysis described in Sect. 1.3.In this section a short presentation of the principle of impedance measurements is described, in order to make the reader familiar with the notation used further in this chapter. The basis for this summary will be typical (Randles-type) equivalent circuit from Fig. 2.6, in which Z f will henceforth mean generally the ac impedance, measured for ac frequency f [Hz] (or angular frequency o ¼ 2pf [rad s À1 ]). The idea of such equivalent circuits, coming from the seminal work of Randles [2], was concordant with the experimental equipment used in early times of impedance measurements. It involved the ac bridge, in which one branch contained the experimental system, the impedance characteristics of which had to be balanced, in the other branch, by the impedance of the electric (equivalent) circuit, possibly closely reflecting the properties of the experimental one.Typically the electrochemical cell is first brought into steady-state, or at least quasi-steady-state (E ss , I ss ) which is further perturbed with the externally applied small amplitude, sinusoidal ac voltage (typically) or ac current. As a consequence, the electrode potential E and the current I will oscillate around their steady-state values with the same frequency o, but in general case exhibiting (frequency dependent) phase difference. In general notation one can denote the phase shifts for both the electrode potential and the current as ' 1 and ' 2 , respectively, and then:M. Orlik, Self-Organization in Electrochemical Systems I, Monographs in Electrochemistry,

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“…2H ad / H 2 (4) or by the Heyrovsky mechanism, which is an EleyeReidel type reaction, where a proton and an electrons react directly on an adsorbed atomic H atom to form Hydrogen [21].…”

Section: Effect Of Electrolyte Concentrationmentioning

confidence: 99%

Electrochemical performance of tungsten electrode as cathode for hydrogen evolution in alkaline solutions

Badawy

Nady

2015

International Journal of Hydrogen Energy

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A theory of overpotential

Abstract: The principal mechanism to be considered in any theory of overvoltage is that of the formation of hydrogen molecules. These may be for:. ed in two ways: either by atomic association

Cited by 116 publications

References 10 publications

A theoretical evaluation of possible transition metal electro-catalysts for N₂reduction

A theoretical evaluation of possible transition metal electro-catalysts for N₂reduction

Application of Impedance Spectroscopy to Electrochemical Instabilities

Electrochemical performance of tungsten electrode as cathode for hydrogen evolution in alkaline solutions

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A theory of overpotential

Abstract: The principal mechanism to be considered in any theory of overvoltage is that of the formation of hydrogen molecules. These may be for:. ed in two ways: either by atomic association

Cited by 116 publications

References 10 publications

A theoretical evaluation of possible transition metal electro-catalysts for N2reduction

A theoretical evaluation of possible transition metal electro-catalysts for N2reduction

Application of Impedance Spectroscopy to Electrochemical Instabilities

Electrochemical performance of tungsten electrode as cathode for hydrogen evolution in alkaline solutions

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Product

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A theoretical evaluation of possible transition metal electro-catalysts for N₂reduction

A theoretical evaluation of possible transition metal electro-catalysts for N₂reduction