Hydrogen evolution on gallium, indium-gallium and mercury-gallium electrodes

Abstract

Measurements of hydrogen overvoltage η have been made using dropping electrodes of gallium; 19.2 mole % In—Ga; and 0.122, 0.36, 1.64, and 99.65 mole % Hg—Ga in 0.100 M HClO₄ at temperatures between 30° and 60°C. η increases by 150 mV when 19.2 % In is added to Ga, and by 280 mV when 1.64 % Hg is added to Ga. η is approximately the same for the two liquid Hg—Ga phases in equilibrium across the miscibility gap. The Frumkin equation (which takes into account the effect of the diffuse double layer) fits the experimental measurements. The enthalpy of activation, extra-polated to the reversible potential with correction for the diffuse double-layer effects, is ΔH^≠₀= 17.8±1 kcal for Ga, 21.0±1 kcal for 19.2 % In—Ga, and 22.3±0.4 kcal for Hg. ΔH^≠₀ for indium electrodes is estimated to be 20 kcal, in contradiction to previous experimental values.