A High Power Buckypaper Biofuel Cell: Exploiting 1,10-Phenanthroline-5,6-dione with FAD-Dependent Dehydrogenase for Catalytically-Powerful Glucose Oxidation

Enzymatic biofuel cells generate electrical energy from renewable sources with high selectivity and environmental benefits compared to lithium batteries and traditional fuel cells. For enzymatic fuel cells to become competitive, major improvements in electrode design are required to enhance power density, voltage output, and stability. Here we have developed a freestanding paper biofuel cell comprising redox molecule embedded multiwalled carbon nanotube papers for electrical wiring of enzymes. The drop-coat and one-pot fabrication methods provide flexibility and permit easy scalability of functionalized bioelectrodes via commercially available materials. Buckypaper functionalized with 1,10-phenanthroline-5,6-dione (PLQ) as an efficient electron mediator for fungal-derived FAD-dependent glucose dehydrogenase (FADGDH) shows very high steady-state current densities for glucose oxidation of I max = 5.38 ± 0.54 mA cm –2 at 0.15 V vs SCE at neutral pH. When coupled with a bioinspired protoporphyrin IX buckypaper cathode, the resulting glucose/O 2 fuel cell delivered a power density of 0.65 ± 0.10 mW cm –2 or 24.1 ± 4.7 mW cm –3 at a cell voltage of 0.5 V, limited by the cathode. Galvanostatic and current discharge experiments confirm robust short-term operational performance.