A Study on Poly(thiazine)-MWCNT Nanocomposite Modified Electrodes and their Applications to NADH Electrocatalysis and Biofuel Cells
Date Issued
2008
Date
2008
Author(s)
Wang, Jen-Yuan
Abstract
β-nicotinamide adenine dinucleotide (NADH), the reduced form of nicotinamide adenine dinucleotide(NAD+), is an important coenzyme of dehydrogenases. It plays key biochemical roles in transferring protons and electrons in the metabolic reactions carried out by over 400 dehydrogenases. The direct oxidation of NADH on a bare inert electrode is slow and unobvious due to high overpotentials. Therefore, using enzymatic or electrochemical catalysts to decrease the overpotential has been a proper method. Traditionally, the use of a second enzyme can guarantee the NAD+ (such as diaphorase) formation in natural regenerations. However, the complex procedures of purification and high cost and instability of enzyme become another issues. In this work, a screen printing carbon electrode (SPCE) modified with multi-walled carbon nanotube (MWCNT) and poly(thiazine) was used to enhance the electrocatalytic NADH oxidation for bioelectronic device applications. This thesis consists of three parts. In the first part of this research, we used methylene blue and methylene green as the monomers and prepared a MWCNT-poly(thiazine) nanocomposite film on the SPCE by electrochemical polymerization. By carrying out basic electrochemical analyses, it was found that the MWCNT-poly(thiazine) nanocomposite has a better polymer structure, thus performs better in cycling stability. In the second part, we used amperometric NADH detection to obtain the efficiency of NADH electrocatalysis of the MWCNT-poly(thiazine) nanocomposite. It was found that the MWCNT-poly(thiazine) nanocomposite could achieve preeminent improvement in NADH catalytic efficiency as compared to a bare poly(thiazine) modified SPCE. As for the MWCNT/PMB electrode, the sensitivity was increased from 0.58 μA mM-1cm-2 (PMB) to 38.95 μA mM-1cm-2 (MWCNT/PMB). Finally, the MWCNT-PMB nanocomposite electrode was used as a bioanode and applied to an ethanol biofuel cell and a glucose biofuel cell, respectively. The preliminary experiments indicated that the MWCNT-PMB nanocomposite could enhance the power density of these biofuel cell systems. For the ethanol biofuel cell, the power density was increased from 1.8 to 2.76 μW cm-2. The glucose biofuel cell could achieve 10.5 μW cm-2 with the modification of the MWCNT-PMB nanocomposite. After further improvement for electrode preparation, the glucose biofuel cell could perform an efficiency as high as 24.25 μW cm-2.
Subjects
β-nicotinamide adenine dinucleotide
dehydrogenase
ethanol biofuel cell
glucose biofuel cell
multi-walled carbon nanotube
poly(methylene blue)
poly(methylene green).
Type
thesis
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