Study On The Cathode And Anode Of Enzymatic Biofuel Cells

Enzymatic biofuel cells (BFCs) are the special devices that utilize biocatalysts to converse chemical energy into electrical energy. Making use of glucose, lactate, oxygen and other substances of metaboliter in vivo, BFCs have potential applications in heart pacemakers, biosensors, heart valves and other implantable electronic devices. The study of BFCs has attracted much attention both from basic study and practical applications in the biochemistry field. However, it has been recognized that poor stability and the low performance of the BFCs have greatly impeded the wide applications of the BFCs. This dissertation focuses on the key points of BFCs to develop the high stability and performance of enzymatic biofuel cells on the development of new material. The works undertaken here can be briefly summarized as follows:1. For key issues of the low power density in BFCs, we choose 2, 2′- azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) to act as the effective redox mediator for laccase in the biocathod for the reduction of oxygen, and ground on the SWNTs as conducting matrix to immobilise ABTS by using theπ-πstacking interaction. Compared with the ABTS free SWNTs bioanode, the ABTS/SWNTs can function as a more effective mediating system in the laccase-catalyzed electroreduction of oxygen. The output yielded in the concomitant oxidation and reduction processed at the bioanode and biocathode electrodes was about 20μW·cm-2 when the constration of glucose was 40 mM in the air atmosphere.2. Over 300 dehydrogenases are known that are dependent on the nicotinamide adenine dinucleotide coenzyme in its reduced(NADH) and oxidized (NAD+) forms. We describe a simple but efficient technique for immobilizing NAD+ by using theπ-πstacking interaction between SWNTs and adenine moiety in NAD+ molecule. On the other hand, methylene green (MG) can be easily adsorbed onto the SWNTs and after polarization, it can used as an effective catalyze for NADH and after crosslinking with GDH, we got the integrated bioanode GDH/polyMG/SWNTs modified electrode. The study developed integrative nanostructured bioelectrochemical biosensors based on chemical-to-electrochemical energy transformations occuring in the biofuel cell combining that the SWNTs as conducting matrix to immobilise the redox mediator ABTS and laccase studied in the last work. Amperometric current verse the glucose concentration range from 1.0 mM to 11.0 mM showed better linear response to produce the calibration curve that provide a simple and convenient way to evaluated the constration of glucose in human serum.3. This study compares the electrochemical activity of four kinds of carbon materials, i.e. single-walled carbon nanotubes (SWNTs), pristine graphene oxide nanosheets (GONs), chemically reduced GONs, and electrochemically reduced GONs, with potassium ferricyanide (K3Fe(CN)6), b-nicotinamide adenine dinucleotide (NADH) and ascorbic acid (AA) as the redox probes. Cyclic voltammetry (CV) results demonstrate that the electron transfer kinetics of the redox probes employed here at the carbon materials essentially depend on the kind of the materials, of which the redox processes of the probes at SWNTs and electrochemically reduced GONs are faster than those at the pristine and chemically reduced GONs. The different electron transfer kinetics for the redox probes at the carbon materials studied here could be possibly ascribed to the synergetic effects of the surface chemistry (e.g., C/O ratio, presence of quinone-like groups, surface charge, and surface clean) and conductivity of the materials. This study could be potentially useful for understanding the structure/property relationship of the carbon materials and, based on this, for screening and synthesizing advanced carbon materials for electrochemical applications.