Acta Chimica 128. (1991)

2. szám - Szabó Kálmán–Mika József: Temperature-dependence of the capacitance of electric double layer at the gallium electrode

Acta Chimica Hungarica 128 (2), pp. 195—205 (1991) TEMPERATURE-DEPENDENCE OF THE CAPACITANCE OF ELECTRIC DOUBLE LAYER AT THE GALLIUM ELECTRODE Kálmán Szabó* and József Mika (Department of Physical Chemistry and Radiology, L. Eötvös University, H-1088 Budapest, Puskin и. 11/13) Received April 27, 1989 Accepted for publication August 23, 1989 The temperature-dependence of the capacitance of the double layer was investi­gated at the liquid gallium electrode in 1 mol/dm3 HC1 and HC104 solutions. It was found that in the temperature interval investigated (305 — 333 K) the capacitance increases or slightly changes with temperature at a surface charge <pvi = constant. Starting from the Damaskin—Frumkin model, the capacitance of the dense part of the double layer, Сц, was calculated at different temperatures as a function of дм- Capacity — charge curves obtained from experimental results and calculated on the basis of the model agree relatively well in the case of HC1 solution, while in the case of HC104 solution this agreement is less satisfactory. This latter finding can be pre­sumably explained in terms of the structure breaking effect of CIO 4 ions at the Ga/H20 boundary layer. Investigation of the capacitance of the electrode—electrolyte boundary layer is one of the possible modes to acquire knowledge on the structural characteristics of electric double layer. The temperature-dependence of the capacitance of the double layer yields further information on the structure of the double layer, particularly on the behaviour of the solvent, on the cor­rectness of the double layer model. Relatively few publications are dealing with the investigation of the dependence of capacitance on temperature [1—8]. Graham [1] investigated the temperature dependence of the capacitance of the double layer, Cd, at the mercury electrode in aqueous NaF solutions of various concentrations, and found that the capacitance of the dense part of the double layer, the Helmholtz layer (Ch) may decrease and also increase with temperature, depending on the surface charge of the metal (дм)- Ribalka studied at the Pb‘electrode [2], Leikis at the Cd electrode [3], the dependence of the capac­itance of the double layer on temperature. According to their measure­ments [2, 3] the direction of the change with temperature of Ch depends also on the value of дм, but while in the case of Hg [1] Ch decreases with increasing temperature in the case of charge values дм <C 0; дСн/дТ 0, * To whom correspondence should be addressed.

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