Various carbon materials, including carbon nanotubes and amorphous carbon, were successfully deposited on the nickel and copper cathodes during the electrolysis in the molten CaCl2-LiCl at 3.0 V and 600 degrees C. CaO serving as trapping agent of CO2 was added before the electrolysis. Electrode reactions were investigated by cyclic voltammetry and chronoamperometry in a three-electrode cell. The results show that the electro-reduction of carbonate ions is dominated by carbon deposition on Ni electrode accompanied with partial evolution of CO, while, on the contrary, the generation of CO is more preferable than carbon deposition on Cu electrode. Electro-reduction of solid carbon were carried out in two-electrode cell and short-time electrolysis were applied to study the formation and growth of the varied carbon microstructure. The formation of carbon nanotubes may be attributed to the evolution of CO. With a SnO2 anode, O-2 gas was produced during the electrolysis. (C) 2017 The Electrochemical Society. All rights reserved.