Copper-doped ceria on carbon fibers for high specific capacitance supercapacitors

Ceria (CeO2) is an attractive candidate for supercapacitors because of its multiple valence states and chemical stability; however, its specific capacitance remains to be further improved. In this work, large specific surface area, highly porous, and copper doped CeO2 is successfully coated on carbon cloth fibers (Cu-CeO2@CC) through a facile molten salt method. The optimized electrode (0.03 Cu-CeO2@CC) delivers an excellent capacitance (1613.4 mF cm−2/764.7 F g−1 at 5 mA cm−2) with satisfying cycling stability (83.5 % capacitance retention upon 10,000 cycles). The DFT calculation results reveal that copper doped into CeO2 lattice leads to an enhanced conductivity and also the potassium adsorption capability. In corporation with Co3O4 electrodeposited on carbon fibers (Co3O4@CC), the assembled asymmetric supercapacitor delivers a maximum energy density of 0.32 mWh cm−2 at the power density of 3.75 mW cm−2. The electrode synthesized herein thus shows great promise for energy storage devices.