Electrochemical impedance spectroscopy study of a hydrogen electrode reaction at a Zn electrode in a molten LiCl-KCl-LiH system

摘要

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 <= eta <= 0.35 V and over the H- concentrations of 1.5 x 10(-4) <= C-H(-) <= 1.2 x 10(-3) mol cm(-1). The logarithm plot of the charge-transfer resistance against the overpotential at C-H = 3.0 x 10(-4) mol cm(-3) gives the symmetry factor, beta, of 0.50 and the exchange current density, j(0), of 5.8 x 10(-3) A cm(-2), respectively. Analysis of the dependence of j(0) on H- concentration independently gives a beta of 0.55. The reasonable beta values indicate that the H- reversible arrow H-ad(M) + e(-) step is rate-determining.