The Cathodic Process Of Electrodepositon Of Carbon Film In Molten Salts

The deposition of carbon film by electrochemical reduction of carbonates in molten salt has some advantages of low temperature, much easier operations and less expensive products, comparing with the most frequently used methods of physical vapor deposition and chemical vapor deposition. In order to further understand the electrochemical mechanism during the electro-deposition in molten salts, and to provide the theoretical foundation for its industrialization, it is necessary to investigate the cathodic process during the deposition. In this paper, the cathodic behavior of CO32-ions is investigated by cyclic voltammetry and chronoamperometry on the electrodes of graphite, titanium, oxide-scale-coated titanium and aluminum in LiCl-KCl-K2CO3melt at450℃; the possibility of the carbon and nitrogen co-electrodeposition is also considered.The results show that CO32-is reduced in a single step on the graphite, titanium, oxide-scale-coated titanium and aluminum in LiCl-KCl-K2CO3melt at450℃. And the reduction currents increase with the potential becoming more negative. The reduction of CO32-is most favorably on the graphite among these substrates. Moreover, the deposition potential should be more negative than the start potential of CO32-reduction, but less negative to avoid the formation of LiCx on titanium and graphite electrodes or alloy on aluminum electrode, which is important to obtain a continuous carbon film on the substrates.Finally, cyclic voltammetry is also carried out on titanium and aluminium after the addition of KNO3into the LiCl-KCl-K2CO3melt. The results show that metal oxide and NO2-are firstly produced by NO3-reacting with metal, whose starting potential is more negative than the reduction of CO32-and adjacent to the start deposition potential of lithium. Much lithium will be produced with the reduction of NO3-.So carbon and nitrogen may not be deposited in a step in the melt.