Facile synthesis of porous CuO/Cu2O/Cu composite powders for hybrid supercapacitors

In this research, CuO/Cu2O/Cu composite powders were prepared by solution combustion synthesis method by using copper nitrate as oxidant and organic fuels. The effects of fuel type, including citric acid, glycine, urea, polyvinylpyrrolidone, and lysine, on the physicochemical and electrochemical properties were analyzed by various characterization techniques. The powders synthesized using urea had the highest amount of Cu2O phase (44.9 wt%). However, the highest amount of CuO phase (97.6 wt%) was obtained by the polyvinylpyrrolidone fuel. Except for the urea fuel with an agglomerated microstructure, the other composite powders had a porous structure with large porosities. The composite powders prepared with glycine fuel containing a mixture of CuO and Cu2O phases had the highest specific capacity of 1480 and 1117 F g−1 at the current densities of 1 and 10 A g−1, respectively, which was equivalent to the capacity retention of 75.5 %. The Cu/CuO/Cu2O//activated carbon hybrid capacitor showed the comparable performance of electrochemical energy storage, including an energy density of 9.7 Wh kg−1 at a power density of 750 W kg−1.