Isotope Effects in Electrochemical Proton Discharge

Conway, B. E.; Salomon, Mark

doi:10.1002/bbpc.19640680405

Cited by 30 publications

(14 citation statements)

References 40 publications

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“…In previous papers,8-13 we have examined how the steps (I) and (Ill) may be distinguished in terms of the H/D separation factor SD and shown 8, 9 that step (1) can be associated with SD + 3 while step (111) can give SD = 6-7. Corresponding ratios R 10 of exchange currents for €32 and D2 production in pure HzO and D20 solutions can be similarly diagnositic of mechanism and proton-tunnelling effects can be indicated by anomalous Tafel slopes and potential dependence of S D .…”

Section: Mh+hm-+h2mentioning

confidence: 99%

“…The strength of the analogy to acid-base reactions depends on the model considered for the activation process and the reaction in the electrochemical proton transfer case. If the H entity is transferred as a proton interstitially to surface sites (e.g., at Pt 9) or into the metal (Pd, Ni, Fe) containing formally one excess electron per ion transferred, the analogy to acid-base reactions of the kind AH+ + B-+A + BH is close. However, if electron transfer occurs '' adiabatically " 18 or " non-adiabatically " by tunnelling 199 20 to an activated complex, (e.g., see ref.…”

Section: Mechanisms Of Proton Transfermentioning

confidence: 99%

“…A third case (A) corresponds to the " dual site " model of the activated complex 9 and represents the case where the proton is discharged between two metal atoms and below the surface tangential to the outermost layer of surface atoms.9~ 11 The terms kl and k2 refer to the 0-Hf and M-H stretching force constants, respectively, and k,, ka, kj and kA are bending force constants for the activated complexes considered; the origin of these data is discussed in ref. (9). A fourth case is shown (0) which corresponds to the activated complex model proposed by Bader.40 In this model, the contribution to the isotope effect from the symmetric mode in the activated complex is relatively small in comparison with that from the degenerate bending mode.…”

Section: 'H30+ F D S O + F;h 'Hzdo+mentioning

confidence: 99%

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Classical and quantum-mechanical effects in electrochemical proton discharge, and the kinetics at low temperatures

Salomon¹,

Conway²

1965

Discuss. Faraday Soc.

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In previous studies of the kinetics of electrocheniical proton discharge, it has been implicitly assumed that an " adiabatic " electron transfer mechanism is involved, i.e., the reaction involves an activated complex which is partially (or totally) neutralized. In a previous treatment of the activated complex in rate-determining proton discharge, it was shown that the H/D separation factor SD could be expected to be related to the ratio of exchange current densities R only on the assumption that the activated complex retains its full charge in the activation process. In the present paper, SD and R are shown to be related by reference to experimental and theoretical considerations for an assumed fully charged transition state, and on the basis that proton tunnelling contributions to the rate are not appreciable. Experimental evidence in support of the latter contention is given by low-temperature kinetic studies down to -125 and -150°C in supercooled alcoholic solutions. A model of the activated complex in proton discharge is considered and involves a " non-adiabatic " electron transfer process. In these terms, the activated complex (particularly that for H+ transfer into Pd) is analogous to that in acid-base proton transfer processes ; the electrode plays the role of a base with variable base strength ; the theoretical treatment of Bader based on Platt's calculations of force constants can be applied, giving an account of the potential dependence of SD.

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Section: Mh+hm-+h2mentioning

confidence: 99%

Section: Mechanisms Of Proton Transfermentioning

confidence: 99%

Section: 'H30+ F D S O + F;h 'Hzdo+mentioning

confidence: 99%

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Classical and quantum-mechanical effects in electrochemical proton discharge, and the kinetics at low temperatures

Salomon¹,

Conway²

1965

Discuss. Faraday Soc.

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“…A value of 1200 cm -1 for v*mb was chosen empirically because it seems to be quite reasonable by comparison to observed frequencies for stable molecules (29,32,35,42).…”

Section: Discussionmentioning

confidence: 99%

Primary and Solvent Isotope Effects in the Anodic Evolution of Oxygen

Salomon¹

1967

J. Electrochem. Soc.

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This equation is plotted for x = 0 in Fig. 8 and is plotted as a function of x for different values of t/T in Fig. 9.The above examples were intended to illustrate the general procedure for employing the lumped parameter models in the computation of concentration transient responses. Even though we have restricted these examples to a constant current excitation, other types of current excitations can readily be considered in a similar manner. In particular, for other excitations the lumped parameter approach becomes even more attractive. This follows because the solution of the diffusion equation, Eq.[13], is practically intractable except for very few excitations, such as the constant current excitation. ConclusionsThe incremental model has been shown to be a convenient vehicle with which to study electrical conduction phenomena in the electrolyte of a reversible transference cell. The linear relationship between concentration and current, for the approximations set forth, suggests a tangible means for describing a distributed system with a circuit analog. This follows because the same system can be analyzed for different excitations without recourse to the exact partial differential equations which are, in general, more difficult to solve than differential-difference equations. Even though the lumped parameter model has its principal limitation in predicting rapid transients, such as the initial portion of the concentration transient for a constant current excitation, its iterative structure provides a convenient means for adding more increments to the model to improve the accuracy. For many applications, where the over-all transient is to be investigated, a two-increment model for the half-cell should be adequate.The possibility of extending and applying the lumped parameter model to other electrolytic systems should pose some challenging and interesting problems. ABSTRACTThe use of hydrogen isotopes in studying the oxygen evolution reaction (o.e.r.) is discussed. It is shown that along with other experimental data such as pI-I studies, Tafel behavior, etc., the H/D-isotope effects can be used as additional criteria for the elucidation of reaction mechanisms. Normal isotope ) unless CC License in place (see abstract).

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“…Although the first experimental suggestion of quantum mechanical effects in PT/CPET in an electrode process was reported by Bawn and Ogden in 1934, 18 and many leading electrochemists, such as Conway, [69][70][71][72][73][74][75][76] tried to confirm this phenomenon, the experimental observation of quantum electrode processes was hampered by several issues:…”

Section: Introduction To the Observation Of Quantum Effects In Multi-mentioning

confidence: 99%

Advances and challenges for experiment and theory for multi-electron multi-proton transfer at electrified solid–liquid interfaces

Sakaushi

Kumeda

Hammes‐Schiffer

et al. 2020

Phys. Chem. Chem. Phys.

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Isotope Effects in Electrochemical Proton Discharge

Cited by 30 publications

References 40 publications

Classical and quantum-mechanical effects in electrochemical proton discharge, and the kinetics at low temperatures

Classical and quantum-mechanical effects in electrochemical proton discharge, and the kinetics at low temperatures

Primary and Solvent Isotope Effects in the Anodic Evolution of Oxygen

Advances and challenges for experiment and theory for multi-electron multi-proton transfer at electrified solid–liquid interfaces

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