| Description |
Research on biofuel cells is the interdisciplinary combination of fuel cells and biotechnology. Like conversional fuel cells, biofuel cells convert chemical energy into electrical energy by catalyzing redox reactions at the cathode and anode and manage the flow of electrons and charge-compensating positive ions to form a complete electric circuit. Unlike conventional fuel cells, biofuel cells utilize living organisms, organelles, enzymes, or DNA as catalysts to facilitate the charge transfer. Most of the current biofuel cell technology utilizes mediated enzymatic system at the anode. It is of interest to employ enzymes that can act as "electron transducers" and directly convert the chemical signal to an electrical one through internal charge transfer without any electron shuttling mediator which could result in poor electrochemistry, limited lifetimes, and complicated fabrication methods. The goal is to utilize direct electron transfer (DET) capable pyrroloquinoline quinone (PQQ)-dependent enzymes to fabricate mediatorless bioanode, which will add versatility and simplicity to biofuel cell technology. There are two approaches to optimize DET biofuel cell performance: (1) to use enzymes in a series to perform multiple-step oxidation of fuel to release the maximum amount of chemical energy stored in each fuel molecule, which allows for enhanced fuel utilization and higher energy density of the fuel cell and (2) to modify enzyme immobilization techniques in order to increase the electron transfer efficiency of each enzyme molecule. In this thesis, a novel bioanode design to perform complete oxidation of glucose will be described. A six-enzyme cascade is immobilized on a carbon fiber paper electrode to stepwise oxidize glucose to carbon dioxide. A further study of the impact of DET enzyme orientation on direct bioelectrocatalysis is carried out by isotropic immobilization of DET enzymes on flat surface gold electrode. A modern method to facilitate electron transfer is also studied by utilizing conducting polyaniline film to covalently bond the PQQ-dependent enzymes to the high surface area polymer matrix. |
