Enzyme-based bioelectrocatalysis and its application to enzymatic biofuel cells

Orateur : Seiya TSUJIMURA (University of TSUKUBA, Tsukuba, Japan)

Enzymatic biofuel cells (EBFCs) are a type of fuel cells, which employ redox enzymes instead of conventional noble metal catalysts (Figure 1). The working principle is the same as in conventional polymer electrolyte membrane fuel cells, namely fuel is oxidized at the anode side and the electrons reach the cathode, where they combine with an oxygen to water. EBFCs are promising for sustainable, ubiquitous, green energy applications ; however, they have two critical problems ; short lifetime and poor power density, both of which are related to a low stability of the enzyme under the working condition, a barrier for the electron transfer, and limited enzyme loading. To achieve the practical application of EBFCs, my researches so far involves (i) screening of promising redox enzymes, and its characterization and engineering, (ii) theoretical studies of bioelectrocatalysis and designing the electrode based on the theory, (iii) design and synthesis of trailer-made redox mediators, and (iv) porous carbon materials for efficient bioelectrocatalysis, (v) prototype EBFCs. For example, FAD-dependent glucose dehydrogenase [1] and bilirubin oxidase [2] are now most widely used enzymes in the EBFC technologies. The theoretical equations enable quantitative analysis of the bioelectrocatalysis reaction in relation of enzymatic activity [3]. Nanocarbon materials, such as carbon blacks and mesoporous carbon, successfully improved the performance of enzyme electrodes [4]. Various kinds of EBFCs have been reported so far [4-7]. Strategies for the designing of hierarchically structured supports composed of mesoporous and macroporous are considered : the large surface area of mesoporous materials can increase the stable enzyme loading and electron transfer efficiency, and the macropores enable the efficient fuel transport. In this presentation, Magnesium oxide (MgO)-templated porous carbon are highlighted [8-11]. The essential properties of the materials with respect to the EBFC application are also discussed. A combination of electron transfer technology and porous carbon material would be helpful in achieving a much higher and stable current output, thus contributing to a practical advance in the sustainable energy field.

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