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

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.