The mirage effect: A sensitive probe for electrochemical cell calorimetry

doi:10.1016/0022-0728(93)85007-4

Journal of Electroanalytical Chemistry

Volume 346, Issues 1–2, 10 March 1993, Pages 119-133

https://doi.org/10.1016/0022-0728(93)85007-4 Get rights and content

Abstract

Measurements of the mirage deflection in an electrochemical cell, where Cu electrodeposition and the ferro/ferricyanate reaction occurred, were performed in the dark under a potential step and in ac conditions with the aim of detecting thermal phenomena due to Joule and Peltier effects at the interface. A mathematical model based on the diffusion of thermal and ionic waves into the electrolyte allowed simulation of the mirage deflection in all cases. The experimental conditions under which the model is valid and the thermal effects can be separated from the ionic effects were discussed. Finally, the Peltier coefficient of the ferro/ferricyanate redox couple could also be measured using the ac technique.

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Using probe beam deflection (PBD) to investigate the electrochemical oxidation of silver in perchlorate media in the presence and absence of chloride ions
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The electrochemical oxidation of silver in 0.1 M KClO₄ solutions containing KCl were investigated by cyclic voltammetry (CV) and electrochemical probe beam deflection (PBD). Ag⁺_(aq) ions were the main product of the silver oxidation in the absence of the halide. The formation of Ag⁺_(aq) provoked a beam deflection towards the electrode surface. A beam deflection away from the electrode surface was then observed during the reduction of the Ag⁺_(aq) ions. A convolution analysis yielded a diffusion coefficient of 1.2×10⁻⁹ m² s⁻¹ for Ag⁺_(aq) in this medium. An anodic peak due to the formation of AgCl_(s) film was observed for the oxidation of silver in solutions containing Cl⁻_(aq). As the applied potentials were made more positive in media containing chloride (after the peak due to the AgCl_(s) formation), a flux of ions away from the electrode surface was clearly detected by PBD. This was assigned to the formation of Ag⁺_(aq) ions through the porous AgCl_(s) film structure. Oscillations on the position of the laser beam were present during the oxidation at high chloride concentrations, due to the precipitation of AgCl_(s) from the solution phase. The electrochemical and PBD data were consistent with a dissolution-precipitation mechanism for the AgCl_(s) film formation.
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¹: Present address: Dipartimento di Chimica, Università “La Sapienza”, Rome, Italy.

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The mirage effect: A sensitive probe for electrochemical cell calorimetry

Abstract

Thin Solid Films

J. Electroanal. Chem.

J. Electroanal. Chem.

J. Electroanal. Chem.

J. Electroanal. Chem.

Electrochim. Acta

Electrochim. Acta

J. Electroanal. Chem.

J. Phys. (Paris)