Patternable Nanoporous Carbon Electrodes for Use as Supercapacitors

Abstract

Capacity of electrochemical supercapacitors strongly depends on the specific surface area of electrodes that can be significantly enlarged by incorporating nanoporous morphology. We present patternable nanoporous carbon microstructures, fabricated using simple O2 microwave plasma etching and carbon-microelectromechanical systems processes, for application as supercapacitors. By incorporating a simple O2 microwave plasma etching process prior to the pyrolysis process, nanoporous surfaces with nanoporous sponge-like networks are formed on the pre-patterned negative photoresist structures due to a self-masking effect. These O2-plasma-etched photoresist structures are converted into nanoporous glassy carbon electrodes (average pore size <1 nm) via pyrolysis while retaining the morphology of sponge-like networks. The pore size and surface morphology are controllable depending on O2 plasma etching time. As a result, the surface area and electrochemical capacitance of the nanoporous carbon surface are increased, respectively, by up to 795 times (∼994 m2 g−1) and 28.1 times (23.9 mF cm−2) compared to a bare carbon surface. In addition, arrays of 3D nanoporous carbon microstructures such as cylindrical posts can be simply integrated on the planar carbon electrode surface by adding a photoresist patterning process prior to the O2 plasma etching, enabling a further improvement in capacitance by a factor of up to 37.3.