Effect of iron oxide impregnated in hollow carbon sphere as symmetric supercapacitors.

Iron oxide impregnated hollow carbon spheres (HCS-Fe 3 O 4 ) samples were fabricated by impregnating Fe(NO 3 ) 3 into hollow carbon spheres (HCS) through an incipient wetness procedure and subsequent heat treatment. Through controlling the amount of iron species stored in HCS, different samples were selectively prepared. Pristine HCS and the samples with different Fe 3 O 4 loading (HCS-Fe 3 O 4 -1, HCS-Fe 3 O 4 -2 and HCS-Fe 3 O 4 -3) were characterized by TEM, XRD, TGA and N 2 adsorption/desorption isotherms in detail, respectively. As electrode materials of supercapacitor, their capacitive performances have been investigated by CV, galvanostatic charge/discharge and EIS measurements in two-electrode system using different kinds of electrolytes. Owing to the optimal pore size and partially filled cavity structure, electrolyte ions exhibit easy and reversible transport through HCS-Fe 3 O 4 -2. So that HCS-Fe 3 O 4 -2 presents the highest specific capacitance of 193 F g −1 at a scan rate of 1 mV s −1 and retains 94.75% up to 10,000 cycles. The capacitance performance of this material tested by symmetric system showed even higher value than the results by three-electrode system from some other researches, indicating the potential applications of HCS-Fe 3 O 4 -2 in industrial and energy field. [ABSTRACT FROM AUTHOR]