Chalcocite as a potential material for supercapacitors

Natural copper minerals covellite and chalcocite have been investigated using different electrochemical methods (galvanostatic, potentiostatic, cyclic voltammetry and electrochemical impedance spectroscopy) from the point of view of their capacitive behavior. The highest value of capacitance (about 200 F cm−2) was obtained on chalcocite in electrolyte containing 1 M H2SO4 and 0.5 M CuSO4, but with unacceptable high leakage current. Optimal system from the both criteria is chalcocite in 1 M H2SO4 and 0.1 M CuSO4, where the capacitance of about 110 F cm−2 has been obtained. Copper sheet served as a counter electrode. Electrochemical impedance spectroscopy method had to be adopted for the systems containing high capacitances. The existence of reaction product on the surface of investigated minerals has been established by optical and electron microscopy.