Hollow Carbon Nanorod-Encapsulated Eu2O3 for High-Energy Hybrid Supercapacitors

Carbon nanorods have been synthesized from acetylene and steam using europium oxide nanorods as a template. The resulting carbon exhibits a high conductivity of 4.66 × 105 S/m and a surface area of 1226 m2/g. The Eu2O3 was partially or completely washed from the carbon, creating hollow nanorods. Hybrid supercapacitors were fabricated where the Eu2O3 contributes a redox pseudocapacitance. A gravimetric capacitance of 501.2 F/g for the hybrid cell and 202 F/g for the carbon-only cell was measured at 1 A/g using 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in propylene carbonate as an electrolyte. The hybrid supercapacitor exhibited an excellent energy density of 108 Wh/kg at 1 A/g compared to 43 Wh/g at 1 A/g for the carbon-only supercapacitor.