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

Highlights: • MnO₂ is incorporated into porous and flat 18k Au substrates by bulk electrolysis. • The MnO₂ depositions are characterized using XRD, XPS, FESEM, EDX mapping and AFM. • Electrochemical analysis shows the high specific capacitance of the porous electrode. • The impedance analysis suggests the superior characteristics of porous electrode. • The prepared electrodes prove to be good candidate for high power applications. 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 AuMnO₂ electrode displays higher phase angle (79°) 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.