Designing Highly Efficient Enzyme-Based Carbonaceous Foams Electrodes for Biofuel Cells

VICTORIA FLEXER; BRUN, N.; BACKOV, R.; MANO, N.

Lacanau

Congreso; XII Colloque du Groupe Français de Bioelectrochimie; 2010

Groupe Français de Bioelectrochimie

Today, low current densities produced by biofuel cells is one of the main challenges to address to present them as a plausible alternative to primary batteries. In such context, three dimensional electrode architectures are promising since they would highly increase the reactive surface area and therefore the enzyme loading, allowing for current enhancement. However, as large enzyme loading means larger substrate consumption, electrode materials should be designed to allow simultaneously for large surface area and fast mass transport of fuel. Ideally, electrodes should have interconnected hierarchical porosity.[1] Pores of diameter slightly bigger than the enzyme are needed for efficient enzyme confinement. Beyond, macropores are needed to optimize faster mass transport of fuel. Three-dimensional carbonaceous electrodes with interconnected hierarchical porosity were synthesized through coating a tetrahydrofuran (THF) solution of preformed formophenolic resin into a silica macroporous framework, called Si(HIPE) (HIPE being the acronym for High Internal Phase Emulsion).[2] In a second step, the three dimensional carbonaceous foam electrodes were further modified to prepare both mediated and non-mediated enzyme electrodes. In the first example, we show results for the modification of the carbonaceous foams with a redox hydrogel made of glucose oxidase (GOx) and an electron conducting polymer, PAA-PVI-[Os(4,4'-dichloro-2,2'-bipyridine)2Cl]+/2+.[3] At saturation and under force convection, the glucose electrooxidation current was 13-fold higher on the porous electrode than on a flat glassy carbon electrode modified with the same mass loading of bioelectrocatalyst. In the second example, the carbonaceous foams were modified with Bilirubin Oxidase (BOD). The non-specifically adsorbed enzyme showed a clear direct electron transfer signal for O2 reduction. At 37oC, pH = 7.2 and in an O2 saturated solution, the reduction signal started at 0.45V (vs. Ag/AgCl) and reached 2 mA cm-2 at 0V. We will show that enzyme-modified micro/macrocarbonaceous foams are promising candidates as electrode materials for the elaboration of efficient biofuel cells and biosensors. They produce much higher and stable currents than flat electrodes. The dependence of the catalytic current with the rotation rate suggests that the size and quantity of the macropores is however, not yet fully optimized. The electrode preparation protocol is simple and low cost, and it can be easily adapted to tune the pore sizes. The mechanical strength and the synthetic route allow for the external shape and size of the electrodes to be designed on demand, which is one important feature to incorporate these electrodes into devices.