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Oscillating electrocatalytic systems

1991; Elsevier BV; Volume: 302; Issue: 1-2 Linguagem: Inglês

10.1016/0022-0728(91)85039-r

2590-2954

Mohsine Hachkar, M.Choy de Martinez, A. Rakotondrainibé, B. Beden, C. Lamy,

Spectroscopy and Quantum Chemical Studies

In the first part of this series it was shown that the electrochemical oxidation of formaldehyde on rhodium in alkaline medium could lead to strong and well reproducible current oscillations under potentiostatic control. In this part, an extensive “in situ” investigation of the interface under working conditions is carried out by means of UV-visible reflectance spectroscopy, in order to determine whether rhodium oxides are, or are not, involved in the oscillating electrochemical process. Firstly, to serve as reference, various types of rhodium oxides were grown under given experimental conditions of pH and potential, and characterized by their reflectance spectra. Then, observing the rhodium surface during the electrocatalytic oxidation of formaldehyde, it was possible to show that the current oscillations were accompanied by in-phase significant periodic reflectivity changes. Finally, the dependence of the magnitude of the reflectivity oscillations on wavelength allowed us to suggest that periodic buildup-re- moval of superficial film oxides are involved in the mechanism.