Fabrication of a 1D Mn3O4 nano-rod electrode for aqueous asymmetric supercapacitors and capacitive deionization

Abstract

One-dimensional manganese oxide presents distinctly stable properties and exhibits excellent electrochemical performance in neutral aqueous solution as a supercapacitor. Here, we successfully prepare a variety of Mn₃O₄ nano-rods with different micro-morphologies and nano-structures and show that 107.5 nm Mn₃O₄ long-rod electrodes exhibit a high specific capacitance of 136.5 F g⁻¹ at a current density of 0.1 A g⁻¹. An aqueous asymmetric supercapacitor device with a maximum work voltage of 1.8 V and high power density is fabricated by using Mn₃O₄ long-rods as the positive electrode and reduced graphene oxide as the negative electrode. Moreover, this asymmetric capacitor device displays a remarkable electro-adsorption performance, with a mean rate of 0.90 mg g⁻¹ min⁻¹ of Na₂SO₄ solution and an initial concentration of 500 mg L⁻¹, for capacitive deionization. Furthermore, during the desorption processes, waste energy can power one red LED indicator efficiently for at least 5 min, realizing effective energy re-utilization.