The properties and performance of carbon produced through the electrochemical reduction of molten carbonate: A study based on step potential electrochemical spectroscopy

Abstract

Carbons with BET specific surface areas of 500 m2 g−1 have been produced through the electrolytic reduction of molten Li2CO3-K2CO3-Na2CO3 at the eutectic composition (43.5:25:31.5 mol%) onto graphite at 600 °C and 0.30 A cm−2 under a 60 mL min−1 CO2 gas flow. These carbons have been shown to consist largely of amorphous carbon with some spherical and flake-like conglomerates. Functionalised oxygen has been observed in synthesised carbons using FTIR and XPS. Synthesised carbons have been investigated in 3-electrode cells and analysed using cyclic voltammetry and step potential electrochemical spectroscopy (SPECS) at room temperature. Capacitances as high as 450 F g−1 have been observed at 0.0833 mV s−1 scan rates. The EDLC and pseudo-capacitive behaviour of produced carbons have been analysed and it has been found that the produced carbons behave hybrid capacitors with considerable pseudo-capacitive contributions. The performance of synthesised carbons has been compared to that of activated carbon derived through the chemical activation of carbon from the pyrolysis of coconut husks and to the reported capacitances of commercial activated carbons.