Performance Evaluations of Biofuel Cells Using Biocatalysts Consisting of Mediator and Enzyme Immobilized Carbon Nanotube Based Substrate

Abstract

Enzyme based biofuel cells (BC) utilizing glucose and oxygen fuels are devices converting chemical energy of the fuels to electrical energy with a help of the enzyme based biocatalysts. Because the BC can run even in the physiological conditions, the glucose and oxygen which are flowed in human body can be considered as the fuels for the devices implanted into the human body. In spite of that, there are still problems to be resolved. Especially, the slow reaction rate issue of the biocatalyst should be improved. To address the issue, adopting mediator with the enzyme and substrate materials is a plausible way. When the appropriate mediator is introduced, electron transfer rate for the anodic reactions including glucose oxidation reaction (GOR) and the cathodic reactions including oxygen reduction reaction (ORR) is promoted and as a result, the generated current will increase. To maximize the electron transfer rate and elucidate the electron transfer mechanism, we propose a new electron transfer mechanism, so called, a mediator embedded electron transfer (EMET). With this EMET mechanism, the corresponding mediator that is cheap and has a low-overpotential range for redox reaction is well immobilized on the enzyme and substrate materials, such as carbon nanotube (CNT). More specifically, in terms of anode, glucose oxidase (GOx) enzyme and dye mediators were considered for the purpose, while in cathode, GOx and iron porphyrin mediator were utilized for the goal. The use of the redox couple induced superior catalytic activity of the biocatalysts and BC performance. In this conference, I will explain the related electron transfer theory, the synthetic procedure of corresponding biocatalysts and the configuration and performance of BC utilized.