Formation of a carbon film by the molten salt electrochemical process and its applications

Abstract

Electrochemical formation of a carbon film can be achieved by either anodic oxidation of C22− ions or cathodic reduction of CO32− ions dissolved in a molten salt. A dense and adherent carbon film coating can be achieved by the anodic oxidation reaction. The obtained carbon-coated metal shows advantageous features for a fuel cell separator as well as a current collector for a Li-ion secondary battery. On the other hand, the carbon film obtained by the cathodic reduction of CO32− ions has a micro-porous structure, which is advantageous for an electrochemical capacitor. It is also possible to electrochemically form a porous carbon film on a very thin, dense and adherent carbon film that is electrochemically formed on the metal surface beforehand. The layered carbon film thus obtained shows a high operating voltage span in an electrochemical capacitor. The cathodic reduction process is attractive also from the aspects of fixation and effective use of CO2.