Iron oxide supercapacitor of high volumetric energy and power density using binder-free supersonic spraying and self-healing rGO

Abstract

Iron oxide (Fe2O3) nanoparticles and reduced graphene oxide (rGO) sheets were supersonically sprayed onto a nickel substrate to fabricate flexible supercapacitors. The supersonic impact velocity was adjusted by varying the air chamber pressure from 2 to 6 bar, which facilitated the self-healing of Stone-Wall defects in rGO sheets. Supersonic spraying caused exfoliation of the rGO sheets, which in turn increased the surface area and adherence of the Fe2O3 nanoparticles. The optimal case exhibited a specific capacitance of 1.44 F⋅cm-2 at a current rate of 1.5 mA⋅cm-2 and the energy density was 14.23 mWh⋅cm-3 at 250 mW⋅cm-3. The width of the potential window increased to 1.4 V, implying a significant increase in the energy storage capability. The energy density of the supersonically sprayed Fe2O3/rGO electrode also showed no signs of deterioration even when the increased current density interfered with the electrode performance.