On the impedance of galvanic cells: XXVII. The temperature-dependence of the kinetic parameters of the hydrogen electrode reaction on mercury in concentrated HI

Abstract

The impedance of a dropping mercury electrode in 57% HI (⊂7.6 M) was measured at temperatures between −35° and +25°C. In a certain potential and temperature region, two reactions were found to be proceeding simultaneously: the reversible Hg/HgI4−2 reaction and the irreversible H+/H2(Hg) reaction. Analysis of the impedance data gave information about the impedance parameters of both electrode reactions, and about the double-layer capacity. The temperature-dependences of the transfer coefficient and the exchange current density of the H+/H2(Hg) reaction are reported. The transfer coefficient decreases with temperature. The apparent heat of activation is 21.6 kcal mol−1.