title: Electrochemical impedance spectroscopy study of a hydrogen electrode reaction at a Zn electrode in a molten LiCl-KCl-LiH system.
abstract: 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 < or = eta < or = 0.35 V and over the H- concentrations of 1.5 x 10(-4) < or = C(H)- < or = 1.2 x 10(-3) mol cm(-3). 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, j0, of 5.8 x 10(-3)A cm(-2), respectively. Analysis of the dependence of j0 on H- concentration independently gives a beta of 0.55. The reasonable beta values indicate that the H- <==> H(ad)(M) + e- step is rate-determining.
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Nakajima
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nohira
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Ito