Enhanced electrochemical activities of morphologically tuned MnFe2O4 nanoneedles and nanoparticles integrated on reduced graphene oxide for highly efficient supercapacitor electrodes

Abstract

The morphology of a nanoparticle strongly controls the path of electronic interaction, which directly correlates with the physicochemical properties and also the electrochemical comportment. Combining it with a two-dimensional (2D) material for a layer-by-layer approach will increase its possibilities in applications such as energy conversion and storage. Here, two different morphologies of MnFe₂O₄, nanoparticles and nanoneedles, are developed by a facile hydrothermal approach and sandwiched with reduced graphene oxide for constructing a 2D/3D sandwiched architecture. The rGO planar structure with abundant hierarchical short pores facilitates the thorough utilization of the utmost surface area to permeate the electrolyte within the structure to minimize the accumulation of rGO nanosheets laterally. The ferrite composited with rGO manifests high specific capacitance as the EDLC behaviour surpasses the faradaic pseudocapacitance boosting electrical conductivity compared to the as-synthesized MnFe₂O₄ structures. Benefiting from a 3D structure and the synergetic contribution of the MnFe₂O₄ nanoneedles and electrically conductive rGO layer, the MnFe₂O₄ nanoneedles@rGO electrode exhibits a high areal capacitance of 890 mF cm⁻² and a remarkable specific capacitance of 1327 F g⁻¹ at a current density of 5 mA cm⁻². 93.36% of the initial capacitance was retained after 5000 cycles in 1 mol L⁻¹ Na₂SO₄ indicating its high cycling stability. The synthesis route proves to be beneficial for a comprehensive yield of MnFe₂O₄@rGO nanosheets of different morphologies for use in the sophisticated design of energy-storing devices. This research strongly suggests that nanoparticle geometry, in addition to two-dimensional carbon-based materials, is a critical factor in a supercapacitor design.