The electrochemical studies were carried out in 0.5 M Na2SO4 electrolyte at room temperature. The working electrode was prepared by drop casting the as-prepared active material aliquot (80 μL) on the ITO glass substrate. The aliquot was prepared by ultrasonically dispersing 4 mg of the as-synthesized powder sample in 0.5 mL of isopropyl alcohol, followed by addition of 10 μL of Na fion solution (5%) as binder.