An integrated device of enzymatic biofuel cells and supercapacitor for both efficient electric energy conversion and storage

An integrated device of enzymatic biofuel cells (EBFCs) and supercapacitor (SC) on glass or flexible polyethylene terephthalate for both electric energy conversion and storage has been developed. A glucose/O2 EBFC was fabricated by modifying flavin adenine dinucleotide-glucose dehydrogenase and laccase on multi-walled carbon nanotubes (MWNTs) based buckypaper as bioanode and biocathode, respectively. While the SC was fabricated by sandwiching a poly(vinyl alcohol)-H3PO4 (PVA-H3PO4) electrolyte between two aligned MWNTs/polyaniline electrodes. The integrated device showed lower internal resistance than previous report because of the use of solid state electrolyte PVA-H3PO4. Furthermore, the self-charged device containing two EBFCs and one SC achieved a high charging voltage of 0.8 V and a maximum power density of 608 μW cm−2, which was 1.9 times of that value for two individual EBFCs in series (326 ± 10 μW cm−2). Such a miniaturized device with a light weight and flexible property would enable new opportunity for portable and wearable devices.