ABSTRACT
Enzymatic biofuel cells use enzymes as catalysts to convert the chemical energy of fuels into electricity. The fuels under consideration are monosaccharides such as glucose and fructose, and alcohols such as ethanol and glycerol. The energy density of fuels should also be considered when enzymatic biofuel cells are to be used to power portable devices. A new class of nanostructured carbon materials, three-dimensional monolithic carbonaceous foams, has been proposed to provide hierarchical pore structures for both high surface area and fast mass transport. Carbon nanotube microwires showed higher stability than classical, non-porous carbon fibers with the same loading of redox polymer and enzyme. The carbon nanotube microwires showed fourfold higher oxygen-reduction current density than the conventional carbon fiber in quiescent solution under air. When oxygen is supplied as dissolved oxygen in aqueous solution, mass transport of oxygen becomes a significant rate-limiting step because the solubility and diffusion coefficient of oxygen are low.
