Powering fuel cells through biocatalysis

This chapter focuses on fuel cells powered by biocatalysis and the recent progress made on biocatalytic fuel cell research. Biocatalytic fuel cells are fuel cells which rely upon biocatalytic reactions at the electrodes to convert chemical fuels and oxidants into electrical power, and they have the potential to deliver a simple, inexpensive, miniaturized, and implanted power supply. Contrary to traditional fuel cells, biocatalytic fuel cells are in principle very simple in design and are usually made of an anode and a cathode. These are separated by an electrolyte and a membrane that should prevent mixing of the fuel and oxidant at both electrodes, while allowing the diffusion of ions to/from the electrodes. Catalysts, such as platinum, are used to decrease this overpotential in fuel cell cathodes. The laccases, classed as polyphenol oxidases, are used as biocatalytic anodes, which catalyze the oxidation of diphenols, polyamines, and some inorganic ions, coupled to the four-electron reduction of oxygen to water. Glucose oxidase (GOx) used as biocatalytic anodes is an FAD (flavin adenine dinucleotide) enzyme, which very specifically oxidises β-D-glucose, reducing dioxygen to hydrogen peroxide in the process. Many assembled glucose–O2 biocatalytic fuel cells have been reported in recent years. Katz et al. reported on a biocatalytic fuel cell based on the surface reconstitution of apo-GOx onto FAD, that was previously coupled to a pyrrolo-quinoline quinine (PQQ) relay conjugated to a self-assembled monolayer of cysteamine on gold. A biocatalytic fuel cell reported by Tsujimura et al. is based on polished glassy carbon electrodes modified by MvBOD for the anode and PQQ-GDH from Acenitobacter calcoaceticus for the cathode.