Utilization of Double-Layered Hydroxides for Enhancement of Dissolved Oxygen Reduction in Microbial Fuel Cell: An Approach for the Evaluation of Coulomb Efficiency

Following their successful use as novel bioanodes in Microbial Fuel Cells (MFCs) [1], Lamellar Double Hydroxides (LDH) were tested as promising cathodes for reducing electrons in the presence of dissolved oxygen. The biofilm on anode, allowed oxidation of organic matter, yielding electrons and protons. The electrons circulated in external circuit, whilst the protons circulated in internal circuit, crossing a separator between the anolyte and catholyte. The nickel-aluminium LDH material was synthesized and added by deposition on Carbon Felt fibers (CF). It was then tested as cathode in the MFC. The electrochemical performances of the material were characterized by cyclic voltammetry (VC) and electrochemical impedance spectroscopy (EIS). Moreover, the MFC performance was evaluated from its Coulomb Efficiencies (CE). Two CEs were calculated graphically from the integral of the voltage between initial and final times, i.e. the area of the domain delimited by the representative curve, the abscissa and the vertical lines. One CE was calculated over the whole voltage curve and another from the triangular peak resulting from the addition of the substrate. It was revealed that this electrode allowed much oxygen reduction and therefore much electrical energy than that using non-modified cathode with the MFC inoculated with a fruit peeling leachate. In comparison to enzymatic fuel cell [2], it seemed to be relatively lower. However, the biomolecule (enzyme) is more expensive and difficult to handle experimentally. Thus, the low-cost biomaterials (CF) used in the MFC was very promising for practical application in bioenergy production and treatment of fruit wastes.