The hydrogen electrode reaction involving hydride ion, H-, at a Zn electrode is investigated in a molten LiCl-KCl-LiH system at 673 K. The charge-transfer resistances were measured by electrochemical impedance spectroscopy in the overpotential region of 0.10 ≤ η ≤ 0.35 V and over the H- concentrations of 1.5 × 10-4 ≤ CH - ≤ 1.2 × 10-3 mol cm-3. The logarithm plot of the charge-transfer resistance against the overpotential at C H- = 3.0 × 10-4 mol cm-3 gives the symmetry factor, β, of 0.50 and the exchange current density, j 0, of 5.8 × 10-3A cm-2, respectively. Analysis of the dependence of j0 on H- concentration independently gives a β of 0.55. The reasonable β values indicate that the H- ⇋ Had(M) + e- step is rate-determining.
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