Design and synthesis of CoFe2O4 quantum dots for high-performance supercapacitors

A series of novel CoFe2O4 quantum dots have been synthesized via solvothermal method with different solvents including ethylene glycol, 1,2-propanediol and 1,3-propanediol followed by heat-up route. And the typical monodisperse CoFe2O4 quantum dots possess narrow size distribution. The results indicate that the quantum confinement effects on the electrochemical performance are obvious including the largest initial specific capacitance of 1269.0 F g(-1) at 12 A g(-1), the highest specific capacitance retention of similar to 91.1% after 10000 cycles at 20 A g(-1), and the maximum specific energy value of 25.2 W h kg(-1) at the corresponding specific power value of 4247 W kg(-1). In addition, after a long charge/discharge process at a high current density, it is shown that it's hard to keep the phase stability for CoFe2O4 , and it is certain to transform the element chemical states (especially cobalt) on CoFe2O4 quantum dots' surface. (C) 2018 Elsevier B.V. All rights reserved.