On the potentiodynamic E/I profile at platinum electrodes in molten NaHSO₄−KHSO₄

Abstract

The stationary electrolysis of molten NaHSO₄-KHSO₄ eutectic on Pt electrodes at 185°C yields hydrogen at the cathode and oxygen at the anode with current efficiencies close to 100%^1,2. Although the kinetics of the cathodic reaction have been interpreted in terms of the conventional hydrogen electrode mechanisms, it changes apparently according to the potential region where the reaction takes place, since the steady Tafel slope at low overv61tages is equal to RT/2F and at high overvoltages it coincides with the 2RT/F ratio. This effect appears when either platinized Pt or bright Pt electrodes are used. As the apparent change of mechanism depends on the potential applied to the cathode it is interesting to investigate the response of the hydrogen electrode reactions in Pt/bisulphate melts under potentiodynamic conditions, to attempt an explanation of the above mentioned change of mechanism