Hybrid Glucose/O₂ Biobattery and Supercapacitor Utilizing a Pseudocapacitive Dimethylferrocene Redox Polymer at the Bioanode

Small implantable electronic devices require biologically compatible energy sources that are capable of delivering quick high-energy pulses. Combining batteries and supercapacitors allows for high power and energy density while providing both small size and biocompatibility. Here, we report a hybrid supercapacitor/biobattery whereby an oxygen-reducing cathode of bilirubin oxidase immobilized with anthracene-modified carbon nanotubes and tetrabutylammonium bromide-modified Nafion is coupled with a glucose bioanode of flavin adenine dinucleotide-dependent glucose dehydrogenase. The redox polymer, dimethylferrocene-modified linear poly­(ethylenimine), used at the bioanode simultaneously immobilizes enzyme, mediates electron transfer, and acts as a pseudocapacitor where capacitance of the anode scales with increased polymer loading. Both multiwalled carbon nanotubes and carbon felt incorporated into the anode construction improve polymer conductivity, subsequently resulting in further improved anodic capacitance. A supercapacitor/biobattery device of the above configuration results in a specific capacitance of 300 ± 100 F/g, which is over 4 times higher than that of other reported biologically derived supercapacitors.