For the alleviation of the global energy crisis, biofuel cell technology offers sustainable and environmentally friendly solutions for energy production. Enzymatic biofuel cells (EBFCs), a subclass of fuel cells, can produce electrical power from renewable fuels by employing biodegradable catalysts (i.e., enzymes), and have therefore attracted researchers’ interest. Further, graphene arranged in three dimensional (3D) structures with excellent electric conductivity and high surface area has been widely used in bioelectrode fabrication for EBFCs. The aim of this Ph.D. project is to develop EBFCs by utilizing 3D graphene-based electrodes as supports for enzyme immobilization to convert chemical energy directly into electricity. In this Ph.D. project, graphene-based 3D electrodes have been constructed by depositing graphene oxide (GO) nanosheets on 3D porous carbon paper via π-π interactions. The improved hydrophilicity of the carbon paper after functionalization with GO ensured the uniform immobilization of aqueous graphene-based nanomaterials and enzymes.
The as-prepared graphene-based electrodes was first applied to design human sulfite oxidase (hSO) bioanodes by drop-casting positively charged graphene-polyethylenimine composites. The assembly of the hSO bioanode and a commercial platinum biocathode allowed the construction of sulfite/O2 EBFCs, outperforming the best reported sulfite/O2 EBFCs. Myrothecium verrucaria bilirubin oxidase (MvBOx) biocathodes based on the graphene-based 3D electrode was then fabricated. The grafting of 4-aminobenzoic acid played important roles both in the orientation of BOx and in the alleviation of produced graphene aggregation. The bioelectrode showed an outstanding operational mainly due to the strong covalent bond between the enzyme and electrode surface. The fabricated bioelectrodes were finally exploited in a gas diffusion electrode configuration producing higher catalytic current densities than the immersed-type. Finally, an EBFC was constructed with the BOx biocathode and a glucose oxidase based bioanode, showing reasonable performance.