Electrochemical properties of manganese ferrite-based supercapacitors in aqueous electrolyte: The effect of ionic radius

• The capacitance of MnFe2O4 colloidal nanocrystal clusters can be adjusted by the electrolytes.
• The assembly of colloidal nanocrystals should be important for their electrocapacitive features.
• The size of hydrated ions plays the key roles in determining the electrocapacitive features.
• The capacitance of the electrode was the largest when using the potassium hydroxide electrolyte.

The electrochemical performances of symmetric supercapacitors assembled by MnFe2O4 colloidal nanocrystal clusters (CNCs) in aqueous electrolytes were investigated by using cyclic voltammetry, galvanostatic charge–discharge, cycle stability and electrochemical impedance spectroscopy. Results showed that the capacitance of MnFe2O4 CNCs can be easily adjusted by the controlled electrolytes. It was found that the specific capacitances of CNCs-based electrodes were 97.1, 93.9, 74.2 and 47.4 F g−1 for the electrolytes (2 M) containing KOH, NaOH, LiOH and Na2SO4, respectively, at the current density of 0.1 A g−1. The capacitance of the electrode was increased from 56.9 to 152.5 F g−1 with aqueous KOH electrolytes changed from 0.5 M to 6 M. The MnFe2O4 CNCs-based supercapacitor using aqueous KOH (6 M) electrolyte displayed the best cycle stability among all the supercapacitors. Based on the experimental results, the enhancement mechanism of electrochemical performances for the CNCs-based supercapacitors was proposed.

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