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The present study investigated the preparation of solid carbon through the electrolysis of a newly formulated molten salt electrolyte containing CaCO3-Li2CO3-LiCl with a continuous cell voltage of 4 - 6V, and temperatures of 550 and 650°C. The process was carried out in a two-electrode cell using AISI 304 stainless steel electrodes in CO2 gas environment. CO2 gas was captured and electro-converted to solid carbon, and deposited on the cathode surface. SEM images revealed five dominant microstructures: grape-like, tubes, thread-like, spheres, and flakes. These materials consist of 69 - 80% carbon content based on EA analysis. Single wall nanotube structures of 13 - 90nm outer diameter was also detected under TEM analysis. The result revealed that electrolysis voltage and temperature changes affected the microstructures, quantity of the deposited carbon, and the efficiency of electro-conversion process. The size of the carbon microstructures declined, and carbon deposition rate increased as both voltage and temperature were increased. However, it reduced the efficiency of the process, thus using more energy per g of carbon produced.

Electrochemical conversion of CO2 into solid carbon is one of the conversion techniques that had been developed which contributes in the carbon capture and utilisation (CCU). The electro reduction process in molten alkali/earth alkali carbonate salt reduces carbonate ion to form solid carbon and alkali/earth alkali metal oxide. Then, the metal oxide reacts with CO2 to reform carbonate ion. This cycle is called the fixation process. However, at a low operating temperature, the charge transfer of the electrolysis process was low and experience current drop after the operation period was prolonged. These leads to the low production rate of solid carbon. The factor that caused the low charge transfer has been described in this thesis. The motivation of study is to improve the charge transfer at operating temperature range 550 - 570 °C and driven at constant voltage 4V which was previously claimed could promotes high current efficiency at this temperature. Therefore, the main objective was to instigate an experimental understanding of electrolysis process on carbon electrodeposition under different voltage feeding. The voltage feeder was invented as to provide electrochemical agitation in the electrolysis system. The electrolysis system with Double Pole Double (DPDT) switch was developed in the electrolysis system as the voltage feeder. The agitation was done by changing the DC current flow manually to drive the electrolysis process. The gated pulse and alternate voltage feeding operation was described in this thesis. The effect of the voltage feeding on electrolysis in molten Li2CO3- Na2CO-3 K2CO3 with mole ratio (0.44: 0.30:0 .26) and salt mixture CaCO3- Li2CO3- LiCI with mole ratio (0.09: 0.28:0 .63) was studied. The effect of voltage feeding on total charge transfer and carbon yield was studied. The succeed edelector deposited products were characterized through EA,S EM-EDXT, EM, XRD and ATR-FTIR. The results showed the total charge transfer under alternate voltage f

Carbon was successfully deposited on AISI 304 stainless steel rod cathode through electrolysis process in three molten salt mixtures, namely K2CO3-Li2CO3 (mole ratio: 1:1), CaCO3-Li2CO3-LiCl (mole ratio 0.09:0.28:0.63) and CaCO3-CaCl2-KCl-LiCl (mole ratio: 0.13:0.31:0.10:0.45), under CO2 atmospheres as continuous source of carbon. The process were carried out for 1 hour at temperature range 545–585°C and electrolysis voltage of 4.0V to drive the deposition of carbon through electrochemical conversion. EDX analysis on deposited products shown carbon as dominant element (89-98%). SEM revealed carbon with Flakes and grapes aggregation shapes for different salt mixtures. The achieved current efficiency of 83.8%, 80.46% and 92.41% were found in the respective salt mixtures, and energy consumption promotes several ways for efficiency improvement on the electrochemical conversion of CO2.