Highly Efficient Porous Enzyme-based Carbonaceous Electrodes Obtained Through Integrative Chemistry
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Highly Efficient Porous Enzyme-based Carbonaceous Electrodes Obtained Through Integrative Chemistry
Victoria Flexer, Nicolas Brun, Rénal Backov, Nicolas Mano Centre de Recherche Paul Pascal, UPR 8641-CNRS, Université de Bordeaux, 115 Avenue Albert Schweitzer, 33600 Pessac, France. ABSTRACT This work concerns the search for new electrode materials for efficient biofuel cells applications. Using a hard templating method we prepared carbonaceous electrodes modified further with Glucose Oxidase and Os polymer. The glucose electrooxidation current is 13-fold bigger on the porous electrode than on flat glassy carbon for the same enzyme loading. These electrodes are three dimensional and posses hierarchical porosity, to optimize the need for both surface area and efficient fuel delivery Although, the dependence of the catalytic current with the rotation rate suggests that the size and quantity of the macropores is not yet fully optimized, the electrode preparation protocol is simple and low cost, and 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, an important feature to incorporate electrodes into devices. INTRODUCTION Enzyme-based biofuel cells follow the same design principle as classical fuel cells, however with promising advantages in terms of costs, easiness of construction and operating conditions [1]. Precious metal catalysts are replaced by enzymes providing higher specificity, avoiding the need of separating membrane, case and seals, operating at roomv temperature and pressure and in neutral pH. The enzyme immobilization procedure is critical. It should keep the activity of the enzyme, while favoring its electrical connection with the underlying electrode, directly or via a redox mediator. Today, low current densities produced by biofuel cells is one of the main challenges to address. Electrical conductivity, porosity and hardness are among the primary desired characteristics when selecting electrode materials [2]. 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 [3, 4]. Ideally, electrodes should have interconnected hierarchical porosity [1]. Pores of diameter slightly bigger than the enzyme are needed for efficient enzyme confinement. It will be an added advantage, if these pores would in turn posses porous walls (porosity in the order of Å), that serve as multiple anchoring sites. Beyond, macropores are needed to optimize faster mass transport of fuel and circumvent low kinetic diffusion path. Eventually, an intermediate porous configuration has to be achieved since mechanical properties and electrical conductivity strongly rely on porosity distributio
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