Enzymatic fuel cells for electric power generation from domestic wastewater

Abstract

Enzymatic biofuel cells (EFCs), which employ enzymes as a catalyst, convert the chemical energy released from the enzymatic oxidation of fuel into electrical energy. While chemical energy is being generated by the oxidation of fuel with enzymes, electricity is generated simultaneously by the movement of electrons released as a consequence of this chemical reaction from anode through cathode in enzymatic fuel cells. The major problem encountered in EFC studies is the difficult/slow electron transfer between the enzyme and the electrode. To mediate the electron transfer between the enzyme and the electrode's surface, low molecular weight redox compounds called mediators are used in EFC. Higher power generation and minimal interference effects at a lower cell potential are achieved by using a mediator in EFC. The scope of this study is for the development of an enhanced electron transferred EFC with a proper mediator for the generation of electrical energy by the oxidation of glucose in domestic wastewater. Therefore, glucose in domestic wastewater is utilised for energy generation. In this study, Polypyrrole-2-carboxyclic acid was modified with various mediators such as, ferrocene, neutral red and p-benzoquinone, which were tested for this purpose. The maximum power density (100 nW/cm2) was observed for the ferrocene modified electrodes including glucose oxidase and laccase as anodic and cathodic enzyme, respectively. The electrode fabrication step was optimized with respect to the electrode material, its operational potential and the thickness of the polymeric film. The highest current values were obtained from the addition of 10 mM of glucose for the EFC system designed with the gold electrode material and operated with a working potential of 0.45 V. The most suitable polymeric film thickness was achieved in the cyclic voltammetry parameters set up with a scan rate of 50 mV/s and 25 cycles. The optimized EFC was tested in the domestic wastewater of Zonguldak City in Turkey. Ferrocene mediated EFC yielded a power density of 50-200 nW/cm2 for the domestic wastewater. © 2014 WIT Press.