Investigation of electrochemical capacitance of 18k nanoporous current collector incorporated MnO2

Abstract

This paper deals with the fabrication of super capacitor electrode material employing a facile etching process followed by electrodeposition. Nanoporous gold current collector has been fabricated by chemically dealloying commercially available 18k gold having a composition of 74% Au, 24% Cu and 2% Ag, with dilute HNO3 solution. Electrochemically deposited MnO2 over the prepared porous Au electrode exhibits a very high specific capacitance value of 670 Fg(-1) which is about 1.65 times greater than that of MnO2 coated over unetched Au electrode (407 Fg(-1)). Etched and unetched MnO2 coated electrode materials are characterized using XRD, XPS, FESEM with EDAX and AFM. Electrochemical characterization of the obtained hybrid material is evaluated by running several cyclic voltagramms using electrochemical workstation. In contrast to the MnO2 coated unetched Au hybrid electrode system, nanoporous Au-MnO2 electrode displays higher phase angle (79 degrees) and lower time constant (2 ms) derived from the bode plot suggesting a better capacitance value. The high specific capacitances offered with good charge/discharge rates at a potential window of 0-0.8 V, in the scan rate of 100 mV/s for 1000 cycles, exhibiting high-energy storage density of 32.56 wh/kg and 53.6 wh/kg and power density of 366 w/kg and 603 w/kg for un-etched and etched electrodes respectively.