Preparation of 3D electrode microarrays of multi-walled carbon nanotubes/nafion nanocomposites for microfluidic biofuel cells

Three-dimensional (3D) electrode microarrays with multi-walled carbon nanotubes (MWCNTs) reinforced Nafion^® nanocomposites were prepared for microfluidic biofuel cells. The oxidized MWCNTs (ox-MWCNTs) were prepared using chemical reactions with 60% nitric acid solution with pristine MWCNTs at 120 °C for 12 hrs with a nitrogen gas flow environment. Ox-MWCNTs in the range of 1 to 20 wt.% based on the Nafion^® polymer weight were reinforced to Nafion^® nanocomposites by solution casting. The micro-porous structure of the ox-MWCNTs reinforced Nafion^® nanocomposites was prepared by plasma etching for 5 to 20 min. The 10 wt.% ox-MWCNTs reinforced Nafion^® nanocomposite produced stable micro-porous structures of 3D electrodes by 10 min plasma etching. Micro-scale 3D structures of MWCNTs reinforced Nafion^® nanocomposites in a diameter range of 47 to 300 μm were prepared by the micro-stencil assisted casting. To characterize the 3D electrode microarrays, the physical geometry and the reinforced MWCNT dispersion in the nanocomposite structure were examined using a scanning electron microscope (SEM) and an optical microscope. Thermal property measurements of the ox-MWCNTs reinforced Nafion^® nanocomposites with 10 min of plasma etching, and without plasma etching were made. Both showed stable thermal properties over 300 °C. The proposed 3D electrode microarray of MWCNT/Nafion^® nanocomposites with micro-porous structures can be applied to miniaturized fuel cell devices.