Synthesis, characterization and electrochemical properties of Fe/MnO2 nanoparticles prepared by using sol–gel reaction

• The MnO2 nanoparticles were grown using sol–gel reaction of fumaric acid and KMnO4.
• The protonation of δ-MnO2 changes the crystalline phase from δ-type to α-type.
• The addition of Fe metal in MnO2 can enhance the Faradic reaction of Na ion.
• The Fe/δ-MnO2 materials show good specific capacitance and high cycling stability.

The δ-MnO2 has been prepared by using sol–gel reaction of fumaric acid and KMnO4 in a mixed alcohol/aqueous solution, and modified with HCl and ferrous ion (Fe2+) to form different MnO2-based materials possessing different electrochemical properties. These MnO2-based materials have been characterized by BET, XRD, ICP, FESEM, and TEM. The electrochemical performance was measured by CV and charge/discharge tests in 1 M Na2SO4 aqueous solution. From the charge/discharge test, the calculated specific capacitance of the Fe/MnO2 sample was 210 F/g at a specific current of 0.4 A/g. It indicates that Fe-modified δ-MnO2 has well electrochemical properties for supercapacitor applications.