Recent Advances in Biofuel Cells: From Enzyme Immobilization to Implanted Devices
Taking into account that the interface activity was related to the immobilized amount of catalysts and the specific surface of the conductive substrate, 3D structures were designed via the use of carbon nanotubes as building block . Carbon nanotubes exhibit nanowire morphology, biocompatibility and excellent conductivity. Furthermore, nanotube modified electrodes offer a large electroactive surface together with a highly porous three-dimensional structure. The recent advances in term of enzyme immobilization via functionalized films electropolymerized onto nanotube coatings will be described. For instance, the combination of carbon nanotube coating and electropolymerized photoreactive films constitutes an original strategy for the covalent immobilization of proteins by irradiation. We describe, here, the successful electrogeneration of a photoactivatable polypyrrole-diazirine film onto multi-walled carbon nanotube coatings and its use for the covalent binding of proteins .
Moreover, the oriented immobilization of laccase on carbon nanotube was carried out to enhance the direct electron transfer. The possibility to functionalize carbon nanotubes by attaching specific docking sites for enzymes via electrogenerated polymer or pyrene derivatives exhibiting p-stacking interactions will be reported [4,5].
We report also the first example of a glucose/H2O2 biofuel cell operating at 5 mM glucose under air (Figure 1). At a bienzymatic cathode, the direct wiring of horseradish peroxidase achieves the electrocatalytic reduction of H2O2 produced during the oxidation of glucose . This represents a novel alternative to the use of laccases or bilirubin oxidases in conventional glucose/O2biofuel cells for implantable applications.
Taking into account that conductive nanostructured materials such as carbon nanotubes became highly appropriate candidates for the elaboration of biofuel cells and electrochemical supercapacitors, we report here for the first time, the original combination of these two devices. The possibility to recharge supercapacitors with an internal energy source could thus represent a significant improvement for the performance of biofuel cells. In this context, we propose an original hybrid battery-capacitor system using a compression of enzymes-carbon nanotubes as supercapacitors and electrodes for a biofuel cell setup (Figure 1). This hybrid supercapacitor/biofuel cell enables high power discharge cycles, the carbon nanotube disks being continuously recharged through the biocatalytic energy conversion under physiological conditions .
Figure 1: Schematic presentation of the functioning principle of a glucose-H2O2biofuel cell and scheme of the electrochemical double layer supercapacitor – biofuel cell hybrid system.
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