CO2-derived carbon for improving thermal energy storage of molten carbonate

Abstract

Molten salt is an excellent medium for heat transfer and storage in solar thermal power generation. The heat transfer and storage performance of molten salt can be significantly enhanced by adding carbon materials. However, the poor dispersion stability of carbon materials in molten salts remains a big challenge. This work reports a kind of dispersive carbon materials in molten carbonate that possess a unique microstructure and are rich in oxygen-containing functional groups. The carbon material was electrochemically produced in molten salt using CO2 as feeding material, which allowed the salt to wet its surface and thereby resulted in good wetting and dispersion properties in molten carbonate. With a carbon concentration of 0.05 wt%, the specific heat capacity of molten Li2CO3–Na2CO3–K2CO3 increases by 89.6 % from 1.67 J g−1 K−1 to 3.17 J g−1 K−1 and thermal conductivity by 181.9 % from 0.61 W m−1 K−1 to 1.71 W m−1 K−1. Overall, this work opens a new avenue for the application of CO2-derived carbon in efficient heat storage.