Silver Nanoparticle-Induced Growth of Nanowire-Covered Porous MnO2 Spheres with Superior Supercapacitance

We report a facile, low-cost, ultrasound-assisted synthesis of nanowire-covered porous MnO2 spheres with superior supercapacitance at high charging rates with longterm durability. The use of catalytic silver nanoparticles is crucial to the growth mechanism in the initial stage, and the resulting silver oxides later grow the nanowires in such a way that they always terminate the wires, thus automatically covering the structures and increasing conductivity. The optimal Ag2O MnO2 structures have a specific capacitance of 536.4 F/g at 5 mV/s. At a high scan rate of 100 mV/s, only 200 F/g remain for the reported carbon nanotube/MnO2 material with an excellent capacitance at low scan rate (1230 F/g 1 mV/s), while the Ag2O-MnO2 reported here still has 417.2 capacitance retention over 10000 charge/discharge cycles at 5 A/g.