Development of Pyrolyzed Nanoporous Carbon Electrodes with Sponge-like Networks of Mesopores for Use as Supercapacitors

Abstract

We developed patternable nanoporous carbon microstructures fabricated using simple O2 plasma etching and carbon-MEMS for the application of supercapacitors. Carbon-MEMS is a versatile microfabrication technology enabling batch fabrication of micro-/nano-sized carbon structure of complex architecture at a wafer level using conventional UV-lithography and pyrolysis processes. By incorporating a simple O2 plasma etching process prior to the pyrolysis process, sponge-like networks of mesopores and nanoporous surface are formed on the top surface of pre-patterned SU-8 negative photoresist structures due to self-masking effect. These O2-plasma-treated photoresist structures are converted into nanoporous glassy carbon electrodes (average pore size = 0.56 – 0.71 nm) with sponge-like networks of mesopores via pyrolysis without using any complex nanofabrication process. As a result, the surface area and electrochemical capacitance of the nanoporous carbon surface are increased up to ~ 795 (surface area = ~ 994 m2∙g-1) and ~ 29.6 times (24.1 mF∙cm-2 at 5 mV/s) respectively compared to a bare carbon surface. In addition, arrays of 3D nanoporous carbon micro-structures such as cylinders can be simply integrated on the planar carbon electrode surface by adding a photoresist patterning process enabling further capacitance improvement up to 41.9 times. The pore size and surface morphology of the nanoporous carbon are controllable depending on O2 plasma etching time.