(487f) A Nanostructured Hybrid Bioanode Hydrogel for Deep Oxidation of Glycerol

There has been a significant interest lately in the complete oxidation of biofuels to CO₂. The use of multiple biocatalysts allows for deeper biofuel oxidation and thus maximizes the energy density that can be extracted per molecule of biofuel. However, there are still many biofuels for which a suitable biocatalyst is not known. We have recently taken an alternative approach to combine the high catalytic activity of enzymatic biocatalysts with the promiscuous nature of small molecule organic catalysts. We demonstrate the complete electrochemical oxidation of the biofuel glycerol to CO₂ using a hybrid enzymatic and small-molecule catalytic system. Combining an enzyme, formate dehydrogenase (FDH), and an organic oxidation catalyst, TEMPO, we are able to electrochemically oxidize glycerol at a carbon electrode, while collecting as many as 16 e^-s per molecule of fuel. Additionally, we have developed a method to immobilize both FDH and the TEMPO catalyst in a cross-linked hydrogel film at the surface of a carbon electrode which allows for a dramatic increase in the rate of electrocatalytic oxidation of several sugars and short-chain alcohols. A TEMPO derivative was covalently attached to a linear poly(ethylenimine) backbone, and the modified polymer was infused with carbon nanotubes and cross-linked onto the surface of a glassy carbon electrode in the presence of FDH. The use of a nanostructured hydrogel film allows for a porous network through which substrate can freely diffuse and the use of a polyamine provides a high localized concentration of base necessary for the catalytic cycle of TEMPO.