Fuel cell enzymatic catalyst

Bioelectrochemical generation of power by enzymes has also been considered. " " The usage of enzymes as catalysts in fuel cells has been vastly experimented, " and currently some enzymatic fuel cells are being used to produce electricity to power many number of electrical devices, like pumps, valves and pacemakers, or electronic devices, like radios, sensors, controllers, and processors. At present however, enzymatic fuel cells have been... 

An EFC consists of two electrodes, anode and cathode, connected by an external load (shown schematically in Figure 5.1). In place of traditional nonselective metal catalysts, such as platinum, biological catalysts (enzymes) are used for fuel oxidation at the anode and oxidant reduction at the cathode. J udicious choice of enzymes allows such reactions to occur under relatively mild conditions (neutral pH, ambient temperature) compared to conventional fuel cells. In addition, the specificity of the enzyme reactions at the anode and cathode can eliminate the need for other components required for conventional fuel cells, such as a case and membrane. Due to the exclusion of such components, enzymatic fuel cells have the capacity to be miniaturized, and consequently micrometer-dimension membraneless EFCs have been developed [7]. In the simplest form, the difference between the formal redox potential (F ) of the active site of the enzymes utilized for the anode and cathode determines the maximum voltage (A ) of the EFC. Ideally enzymes should possess the following qualities. 

Pt-based catalysts are two necessary approaches at the current technology stage. It is believed that non-noble metal electrocatalysts is probably the sustainable solution for PEM fuel cell commercialization. In the past several decades, various nonnoble metal catalysts for ORR have been explored, including non-pyrolyzed and pyrolyzed transition metal nitrogen-containing complexes, transition metal chalcogenides, conductive polymer-based catalysts, metal oxides/carbides/nitrides/ oxynitrides/carbonitrides, and enzymatic compoimds. The major effort in non-noble metal electrocatalysts for ORR is to increase both the catalytic activity and stability. 

At one of the electrodes at least, the catalyst for the electrochemical reaction are microorganisms (microbial fuel cells) or enzymes (enzymatic fuel cells). 

Many of the significant advances in improving the performance of enzymatic fuel cells can be attributed to the introduction of rationally designed electrode materials, particularly the incorporation of nanoscale materials in macroscale architectures in order to improve electron transfer (ET) from the biocatalyst to the electrode [ 1 -9]. For enzymatic fuel cell electrodes, protein interaction and orientation at the nanoscale is imperative, as the enzyme must be positioned in such a way that its redox center can transfer electrons to the transducer surface [10-15]. Because the aspect ratio of a nanomaterial approaches the molecular scale, redox proteins can establish a close and direct association with the material and effectively decrease the electron tunneling distance. Carbon nanotubes (CNTs), for example, have dimensions that are uniquely amenable to close physical association with proteins and can facilitate direct electronic interactions with redox catalysts [14]. The incorporation of CNTs into... 

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