Performance analysis of a proton exchange membraneless biological fuel cell based on lactate dehydrogenase
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abstract
Fuel cells with enzyme-coated electrodes, commonly known as enzymatic fuel cells, are closely looked at as a means to power implantable medical devices and miniaturized bioelectronic devices such as biomicroeletromechanical or nanoelectromechanical systems (bioMEMS/NEMS). This study attempts to develop a fuel cell with the proton exchange membrane (PEM) totally replaced by an enzyme coating tethered only to one electrode (anode). It was conjectured that the specificity of the enzyme to only a specific substrate at the anode coupled with the selectivity of reactions that could occur at the cathode due to thermodynamic preferences will discourage crossover reactions, making the PEM elimination possible. In the anode, lactate dehydrogenase (LDH), a NAD-dependent oxidoreductase, was immobilized on a gold-coated electrode using a layer-by-layer assembly technique. The LDH-coated anode catalyzed the oxidation of lactate to pyruvate, while Pt was used to catalyze the reduction of oxygen to water. Three parameters were selected to elucidate the behavior of the fuel cell under different load conditions. These parameters (lactate concentration, fuel cell temperature, and feed flow rate) were varied within the human physiological range to evaluate the performance as an implantable fuel cell. The cell reported an average open-circuit voltage of 261.72 0.01 mV, power density of 360.6 nW cm -1, and voltage efficiency of 25.05%. This experiment demonstrated that total elimination of the PEM is possible via coating only one electrode with a substrate-specific enzyme. This is a significant step toward developing power supplies for bioelectronic devices via enzymatic fuel cells, since elimination of the PEM enables unprecedented simplification of the fuel cell architecture (for miniaturization) while eliminating a component that contributes to significant internal resistance. 2012 ASABE.
