Effect of Anode Materials on NF 3 Formation

Abstract

The electrolytic formation of from molten salt, , and , with different anodes, was compared. The current efficiencies for formation on a Ni anode and a LiF impregnated carbon (LiF/C) anode in the melt increased with an increase of the current density and became constant at current densities higher than 120 and 50 mA/cm2, respectively. Current efficiencies on the Ni anode were greater than those on the LiF/C anode in the range of current density higher than 30 mA/cm2. On the other hand, the presence of KF in the melt reduced the current efficiency on both the Ni and the LiF/C anodes, and the current efficiency on the LiF/C anode in the melt decreased with an increase of the current density. According to the surface analyses, the oxide film on the Ni anode polarized in the melt was composed of nickel difluoride, some highly oxidized nickel fluoride, and nickel oxide or oxyfluoride having plural valences. Consequently, highly oxidized nickel fluoride on the Ni anode is considered to function as a mediator of the electrochemical fluorination under discussion.