Electron transfer reactions at metal electrodes: Influence of work function on free energy of activation and exchange current density

2001 ◽  
Vol 115 (13) ◽  
pp. 6173-6178 ◽  
Author(s):  
S. Harinipriya ◽  
M. V. Sangaranarayanan
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Work Function ◽  
Current Density ◽  
Exchange Current ◽  
Transfer Reactions ◽  
Energy Of Activation ◽  
Metal Electrodes ◽  
Electron Transfer Reactions ◽  
Free Energy Of Activation

scholarly journals Relationship between the Energy of Activation and the Overall Free Energy of Bridge-assisted Electron Transfer Reactions in Polar Media.

1973 ◽  
Vol 27 ◽  
pp. 1067-1072 ◽  
Author(s):  
Jens Ulstrup ◽  
Ingegärd Andersson ◽  
Steinar Husebye ◽  
Øyvind Mikalsen ◽  
Kurt Leander ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Transfer Reactions ◽  
Energy Of Activation ◽  
Electron Transfer Reactions ◽  
Polar Media

ChemInform Abstract: Electron Transfer Reactions in Solvent Mixtures: The Excess Component of Solvent Reorganization Free Energy

ChemInform ◽  
2000 ◽  
Vol 31 (37) ◽  
pp. no-no
Author(s):  
M. Morillo ◽  
C. Denk ◽  
P. Perez ◽  
M. Lopez ◽  
A. Sanchez ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Transfer Reactions ◽  
Solvent Mixtures ◽  
Electron Transfer Reactions ◽  
Excess Component

SOME THEORETICAL ASPECTS OF ELECTRON-TRANSFER PROCESSES IN AQUEOUS SOLUTION

1959 ◽  
Vol 37 (1) ◽  
pp. 138-147 ◽  
Author(s):  
Keith J. Laidler
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Free Energy ◽  
Energy Of Activation ◽  
Theoretical Treatment ◽  
Free Energy Of Activation ◽  
Diffusion Controlled ◽  
Entropy Of Activation ◽  
Pass Through ◽  
Electron Transfer Processes

A theoretical treatment has been developed for the rates of electron-transfer reactions in aqueous solution, with particular reference to the ferric–ferrous system. The reactions are considered to be diffusion-controlled processes, the approach of the ions being hindered by the electrostatic repulsion between them. Calculations have been made of the free energy of the diffusion process and for the repulsion, account being taken of the variation in dielectric constant with the electric field. The form of the potential-energy barrier between the ions is calculated for various separations, and the transmission coefficient calculated using the quantum-mechanical expression corresponding to a rectangular barrier. The total free energy of activation for the reaction, which is the sum of the contributions due to diffusion, repulsion, and tunnelling, is found to pass through a minimum at a separation of about 4 Å. The calculated free energy of activation for the reaction is 15.4 kcal, in good agreement with the experimental value of 16.8 kcal. The energy and entropy of activation for the reaction are also briefly discussed.

Selected experimental results for electron-transfer reactions

1996 ◽  
Author(s):  
Wolfgang Schmickler
Keyword(s):  
Electron Transfer ◽  
Transfer Coefficient ◽  
Outer Sphere ◽  
Chloride Ions ◽  
Transfer Reactions ◽  
Energy Of Activation ◽  
Trace Impurities ◽  
Electron Transfer Reactions ◽  
Temperature Range ◽  
Straight Line

Innumerable experiments have been performed on both inner- and outer-sphere electron-transfer reactions. We do not review them here, but present a few results that are directly relevant to the theoretical issues raised in the preceding chapters. The Butler-Volmer equation (5.10) predicts that for |η| > kT/e0 a plot of the logarithm of the current versus the applied potential (Tafel plot) should result in a straight line, whose slope is determined by the transfer coefficient α. Because of the dual role of the transfer coefficient (see Section 5.2), it is important to verify that the transfer coefficient obtained from a Tafel plot is independent of temperature. We shall see later that proton- and ion-transfer reactions often give straight lines in Tafel plots, too, but the apparent transfer coefficient obtained from these plots can depend on the temperature, indicating that these reactions do not obey the Butler-Volmer law. In order to test the temperature independence of the transfer coefficient, Curtiss et al. investigated the kinetics of the Fe2+/Fe3+ reaction on gold in a pressurized aqueous solution of perchloric acid over a temperature range from 25° to 75°C. In the absence of trace impurities of chloride ions, this reaction proceeds via an outer sphere mechanism with a low rate constant (k0 ≈ 10-5 cm s-1 at room temperature). Figure 8.1 shows the slope of their Tafel plots, d(lni)/dη, as a function of the inverse temperature 1/T. The Butler-Volmer equation predicts a straight line of slope αe0/k, which is indeed observed. Over the investigated temperature range both the transfer coefficient and the energy of activation are constant: α = 0.425 ± 0.01 and Eact = 0.59± 0.01 eV at equilibrium, confirming the validity of the Butler-Volmer equation in the region of low overpotentials, from which the Tafel slopes were obtained. The phenomenological derivation of the Butler-Volmer equation is based on a linear expansion of the Gibbs energy of activation with respect to the applied overpotential. At large overpotentials higher-order terms are expected to contribute, and a Tafel plot should no longer be linear.

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