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Fuel Cells: Enzymes and Microbes for Energy Production

  1. Frédéric Barrière

Published Online: 18 JAN 2011

DOI: 10.1002/0470862106.ia801

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Barrière, F. 2011. Fuel Cells: Enzymes and Microbes for Energy Production. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Université de Rennes 1, France

Publication History

  1. Published Online: 18 JAN 2011

Abstract

The use of redox enzymes and bacteria as catalysts at the electrodes of fuel cells is reviewed with an emphasis on some inorganic aspects of the research. In biofuel cells, redox enzymes catalyze the oxidation of organic substrates like glucose at the anode or the reduction of electron acceptors like dioxygen at the cathode. Many of the redox enzymes have metal-active sites that are of interest to the bioinorganic chemist. Moreover, efficient electrical linking between a redox enzyme and an electrode requires the mediation of a small electroactive molecule, capable of diffusing and shuttling electrons between the core of the enzyme and the electrode surface. These redox mediators may be coordination or organometallic complexes. In microbial fuel cells, the biocatalysts are living microorganisms, most often bacteria. At the anode, the bacteria metabolize organic substrates like sugars or acetate. In the absence of dioxygen or other natural electron acceptors, some species of bacteria may transfer electrons to the anode of a fuel cell. Different mechanisms for bacterial anodic electron transfer are proposed and discussed in this article. One common feature of these processes is the direct or indirect linking of the electrode surface to the outer-membrane-bound electron-transfer chain of the respiratory system of bacteria. This system contains a chain of redox enzymes containing cytochrome-type active sites that may be directly electrochemically addressed in some cases. At the cathode of microbial fuel cell, some bacteria may also accept electrons and catalyze the reduction of electron acceptors like nitrate, sulfate, and dioxygen. Given the importance of dioxygen reduction in most fuel cells, a perspective is given on the way inorganic chemistry may contribute to the design of efficient electrode catalysts through molecular, material, enzymatic, or biological approaches. Finally, the prospect of self-sustained biological fuel cell is discussed with integration of plants with their anolyte as an in situ fuel provider in the form of root exudates, or enrichment of dioxygen in their catholyte with photosynthetic activity of algae. Although the emphasis is on the inorganic themes of biological fuel cell research, the important multidisciplinary approaches of the topic are put forward. This article also contains discussions on the relative performances and applications of both types of biological fuel cells.

Keywords:

  • redox enzymes;
  • glucose oxidase, laccase;
  • osmium complexes;
  • ferrocenyls;
  • redox mediators;
  • oxygen reduction;
  • electroactive bacteria;
  • biofilms;
  • bioelectrochemistry;
  • wastewater treatment;
  • plant-microbial fuel cells