Study of Electrode Structures and Redox Kinetics in Biofuel Cells

Selection of the anode-cathode electrodes materials and structure is one of the critical challenges of bio fuel cell application. They can affect the power density and columbic efficiency. Two types of bio fuel cell were studied, the Microbial Fuel Cell (MFC) and the Enzymatic Fuel Cell (EFC), where the electrode structure and kinetics are similar except for the rates of redox reaction. The electrochemical characteristics of the In the MFC the anode was inoculated with MRS broth containing Lactobacillus Cesai Shirota. Complete characterisation and optimisation of the redox kinetics will be presented. Mediators will be used to enhance electron transfer between the fuel, bacteria and electrodes to improve electrode kinetics. A fast and convenient bacterial immobilization method will be proposed as an attempt to improve the anode efficiency of a microbial fuel cell, in which bacteria will be entrapped. The electron transfer characteristics with the mediators and immobilizers shall be studied by cyclic voltammetry and SEM imaging. Enzymatic Fuel Cell is a specific type of bio fuel cell that uses enzymes as a catalyst to oxidize its fuel, instead of precious metals. Enzymatic glucose biofuel cells convert chemical energy stored in glucose into electricity. Enzymatic oxidation from complex sugar is carried out by glucose selective enzymes such as glucose oxidase (Gox) and oxygen reducing enzyme namely laccase. These reactions are highly enzyme specific and occur at relatively mild conditions (Neutral pH and ambient temperature). The specific materials and structure for the electrodes used in enzymatic fuel cell can affect the power density and columbic efficiency. This glucose EFC cell features a 3-D porous carbon anode and cathode, for high surface area for the reaction, a suitable immobilizer for the enzyme immobilization and mediators like ferrocene for optimal electron transfer. The achievable cell potential is between 0.7- 0.8V. The achieved power density is still below theoretical value. The EFC will be optimized for enzyme loading; conductive loss minimization, both electronic and ionic, direct charge transfer for improving charge transfer efficiency, and pore channel and size profile.