Electrochemical Fluorination of Room Temperature Molten Salt

摘要

The electrical conductivities of the (CH_3)_4NF·mHF melts (m = 3.5, 4.0, 4.5, 5.0, and 5.5) increased with increasing the m value. In contrast, the viscosities of the melts decreased largely in the range of the m values between 3 and 4 and then decreased linearly with increasing the m value. The IR study revealed that a free HF molecule as well as ions such as (HF)F~-, (HF)_2F~-, and (HF)_3F~- existed in the (CH_3)_4NF·mHF melts (m > 3.0). The ~1H-NMR measurement also indicated that the various forms of the species and the ions having HF existed in the melts and that the number of HF coordinating to F~- ion in the melts increased with the m value. In electrolysis of the melt at room temperature, the anode gas generated on the Ni, the Ni-NiO coating Ni, and the LiNiO_2 coated Ni sheets was composed of CF_4, NF_3, C_2F_6, CHF_3, (CF_3)_3N, C_2F_5N(CF_3)_2, and a few kinds of partial fluorinated amines. The formation ratio of a partial fluorinated amine to the overall anode gas decreased with increasing the m value. The best yield of (CF_3)_3N was obtained with the LiNiO_2 coated Ni sheet anode polarized at 4.0 V in the (CH_3)_4NF·5HF melt.