Electrochemical properties of various enzyme / electrode material interfaces for biofuel cell application

Abstract

Biological fuel cells are a type of fuel cells that contain biological components, like enzymes, proteins and microorganisms that help achieving the transformation of chemical energy into electricity (1). In this kind of fuel cells, a large range of fuels can be used, either organic like sugars, organic acids and alcohols (2, 3, 4) or inorganic like hydrogen (5). Biofuel cells may be a good alternative to platinum based fuel cells where the oxygen reduction and the hydrogen oxidation are both catalyzed thanks to platinum properties. But this metal is rare on Earth and expensive. Reducing its load in fuel cells remains one of the major issues to solve in order to achieve a large scale fuel cell commercialization. One way to do this can be the use of enzymes as catalysts in fuel cell internal processes. Enzymes in biofuel cells can either directly catalyze the electrochemical reactions involved (6, 7) or intervene in intermediate reactions like the regeneration of mediators (2) or in metabolic processes inside microorganisms (2, 5, 8). The direct, or also called mediatorless, electron transfer between enzyme and electrode is the subject of a significant number of works in the field of bioelectrocatalysis and more particularly in the biosensor domain. This is because this kind of mechanisms may simplify the enzymatic electrochemical system and the preparation of the electrode/enzyme interface. In the present work, several enzyme-electrode couples are electrochemically studied with the aim to find new alternatives for both cathodic and anodic reactions in biofuel cells by exploiting the direct electron transfer capability of the enzymes. The results were compared to the platinum behavior and allowed to classify the different systems for an energetic use. The study was made combining a biocatalyst (laccase, hydrogenase, glucose oxidase and hemin) with different electrode materials (titanium, stainless steel, glassy carbon, graphite and DSA). The biocatalysts were confined near the electrode by a dialysis membrane or were adsorbed using a Dimethyl Sulfoxide solution (DMSO). The electrochemical tests were performed using galvanostatic mode and voltammetry.