Biochemical fuel cells

AbstractBiofuel cells transform abundant raw materials into electrical power in the presence of biocatalysts, enzymes, or whole cell organisms. Biomaterials may participate in the biofuel cell activity by either producing fuel substrates or by catalyzing the electron transfer chain between the fuel substrates and oxidizers and the electrodes. Two types of biofuel cell elements are discussed in this review article: microbial‐based biofuel cells and enzyme‐based biofuel cells.Microorganisms may act as microreactors in fuel cells for the generation of the fuel products such as H2or H2S. These fuel products may be generated apart from the biofuel cell and transported to its anodic compartment or, alternatively, may be directly generated in the anodic compartment of the biofuel cell. Different microbial‐based biofuel cells are reviewed in the account.Enzymes are employed as catalysts for the activation of electron transfer chains between the fuel substrate and the anode in the anodic compartment, and between the oxidizer and the electrode in the cathodic compartment. In order to activate the electron transfer cascades between the enzymes and the electrodes, native electron carriers (co‐factors) and artificial electron transfer mediators must be coupled to the biocatalytic transformations. By the nanoengineering of the electrode surfaces with co‐factor/electron‐relay/enzyme assemblies, integrated, electrically contacted, bioelectrocatalytic anodes and cathodes are tailored. Different enzyme‐based biofuel cell configurations are described. The different parameters controlling biofuel cells efficiencies are discussed. The efficiencies of the different biofuel cell configurations are evaluated in terms of the limiting factors and kinetic features of the systems.