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Article

Thermodynamics of the N₂/N^3- Redox Couple in a LiBr−KBr−CsBr Melt

Katsutoshi Kobayashi, Hironori Nakajima, Takuya Goto,* and Yasuhiko Ito

Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan

J. Phys. Chem. B, 2005, 109 (50), pp 23972–23975

DOI: 10.1021/jp053920i

Publication Date (Web): November 25, 2005

To whom correspondence should be addressed. E-mail: goto@ energy.kyoto-u.ac.jp.

Abstract

Nitrogen electrode reaction has been investigated in a LiBr−KBr−CsBr melt containing Li₃N. The reaction N^3- → ¹/₂N₂ + 3e^- is confirmed by quantitative analysis of anodically evolved gas. The Nernst relation holds for the rest potential of Ni electrodes at a nitrogen gas pressure, p_N_₂, of 0.05−1.0 atm and an anion fraction of the N^3- ions, x_N_^3-, of 0.003−0.010 (anion fraction). Then, the standard formal potential of the N₂/N^3- couple, , is evaluated to be 0.251 ± 0.009 V versus Li⁺/Li (p_N_₂ = 1 atm, x_N_^3- = 1) at 673 K. The dependence of on the temperature (570−730 K) gives a linear relation, whose slope is (−0.930 ± 0.117) × 10^-3 V K^-1. Thermodynamic quantities for the formation of Li₃N in the melt are also estimated.