Deposition and Morphology Control of Carbon Film through Electrochemical Reduction of Carbonate Ions in Molten LiCl

Abstract

Synthesis of a compact, uniform, and thick carbon film on nickel substrate were conducted by electrochemical reduction of carbonate ions in LiCl-Li2CO3 molten salt. It was found that the carbon consistently forms into a structure of wire and sphere particle. The uniformity and compactness of the carbon film were found to be dependent on the applied current density, electricity, and the electrolysis method. At lower current densities, the carbon tended to grow locally, resulting in larger-sized wires and particles. At higher current density, a relatively uniform and thin carbon film can be synthesized on the beginning but soon changed to a cluster-like structure. The contradiction between current density and carbonate ions` diffusion limit make it is impossible to obtain a compact and uniform film by using constant current electrolysis. By applying pulsed current electrolysis with an average current density of 10 mA cm-2 and a peak current density of 200 mA cm-2, a compact and uniform carbon film with a thickness of approximately 10 μm was successfully prepared.