Regulation of CO2 molten salt capture and electrolysis to elemental carbon

CO2 molten salt capture and electrolysis for the preparation of elemental carbon materials are considered to be a very promising CCUS technology due to their good selectivity. Efficient CO2 capture and low power consumption for electrolysis are crucial. In this paper, the thermodynamics of CO2 capture to carbonate and theoretical voltage of carbonate electrolysis were calculated. The kinetics of CO2 capture in typical CaCl2-based molten salts were studied. The effects of temperature and voltage on the electrolysis process and power consumption of CO2 electrolysis to elemental carbon were studied in ternary Na2CO3-K2CO3-Li2CO3 molten salts and ternary CaCl2-NaCl-CaO molten salts. The results show that CaO is the best CO2 capture agent compared with alkali metal oxides. The obtained CaCO3 has the lowest theoretical decomposition voltage and power consumption. In the typical CaCl2-3.0 wt%CaO molten salt, CO2 capture capacity is 0.016 gCO2/g. Compared with Na2CO3-K2CO3-Li2CO3 molten salt, CaCl2-NaCl-CaO molten salt has a lower electrolysis voltage and power consumption for CO2 electrolysis to carbon. Under the optimal conditions of 750 ℃ and 1.5 V, the current efficiency is 95.3%, and the minimum electrolytic power consumption is only 14.1 kWh·kg-1.