Electrochemical Behavior of Carbonate Ion in the LiF-NaF-Li2CO3 System

The electrochemical behavior of carbonate ion at a Ni electrode in LiF-NaF-Li2CO3 molten salt was investigated using cyclic voltammetry, square wave voltammetry, and chronopotentiometry. The results show that the electrochemical reduction of carbonate ion to carbon is a simple four-electron transfer that occurs in a one-step process. The reduction of carbonate ion at a Ni-wire working electrode is an irreversible process with diffusioncontrolled mass transfer. The diffusion coefficient of carbonate ion at 973, 993, 1023, 1043, and 1063 K is 4.46 x 10(-5), 4.82 x 10(-5), 5.31 x 10(-5), 5.90 x 10(-5), and 6.54 x 10(-5) cm(2)s(-1), respectively, and the results obey the Arrhenius law, with an activation energy of 35.8 KJ mol(-1). The X-ray diffraction results show that hexagonally structured graphitized carbon can be obtained by potentiostatic electrolysis. Scanning electron microscopy images show that the deposits exhibit a spherical morphology. (C) The Electrochemical Society of Japan, All rights reserved.