On-Chip Micro-supercapacitors Based on Nanoporous-Gold/ MnO2 Hybrid Electrodes

Development of miniaturized electronics has stimulated demand for integration of energy storage units with electronic circuits. Micro-supercapacitors can be a promising strategy for future application in microelectric devices because of their properties of high power density, high-rate capability, long lifetime and high-frequency response. Progress in micro-fabrication technology has enabled on-chip micro-supercapacitors in an interdigitated planar form be compatible with integrated circuit. From a material perspective, nanostructured carbon-based materials are commonly used in electric double-layer micro-supercapacitors. In addition, transition metal oxides such as ruthenium oxide and manganese oxide, and some conducting polymers such as polypyrrole and polyaniline have been used as electrodes for pseudo-capacitive micro-supercapacitors. 

MnO₂-based pseudocapacitive electrodes have been considered as a promising candidate because of their high theoretical specific capacitance (1,370 F/g), environmentally friendly nature and low cost of raw materials. The main drawback of MnO₂ is that the poor conductivity may limit the charge/discharge rate for high-power applications. However, Lang et al. have show that hybrid structures made of nanoporous gold and nanocrystalline MnO₂ have enhanced conductivity, resulting in a specific capacitance close to the theoretical value (~1,145 F/g)[1]. The nanoporous gold not only plays a role as a double-layer capacitor, but also promotes electron transport through the MnO₂ and benefits fast ion diffusion between the MnO₂ and the electrolytes. Besides, the excellent mechanical properties enable nanoporous gold to be amenable to micro-fabrication processes[2]. The high specific capacitances and charge/discharge rates offered by such nanoporous gold/MnO₂ hybrid structures make them promising candidates as electrodes in micro-supercapacitors.

 Herein, we make our efforts in preparing high-performance nanoporous gold/MnO₂ hybrid electrodes by electrodepositon method and fabricating micro-supercapacitors in interdigitated planar form. Our electrodeposited nanoporous gold/MnO₂hybrid electrodes also have a specific capacitance close to the theoretical value (>1,000 F/g). The preparation and performance of hybrid electrodes and micro-supercapacitors will be presented.

1.  Lang, X.Y., et al., . Nature Nanotechnology, 2011. 6(4): p. 232-236.

2.  Jin, H.J. and J. Weissmüller, Science, 2011. 332: p. 1179-1182.