Studies on the application of electrosynthesized poly(2,5-dimethoxyaniline) and its platinum composite electrodes

• Main Authors: Tang-Kuei Chang, 張棠貴
• Other Authors: Ten-Chin Wen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/31075426921432474608

博士 === 國立成功大學 === 化學工程學系碩博士班 === 97 === The main purpose of this dissertation is to study the application of electrosynthesized poly(2,5-dimethoxyaniline) and its platinum composite electrodes, which is divided by three parts including electrocatalytic oxidation of ascorbic acid (AA), methanol sensing, and oxidation. Following are the brief descriptions of each part. Poly(2,5-dimethoxyaniline) (PDMA) films were choronoamperometrically deposited on indium-tin oxide (ITO) electrodes. PDMA films exhibit high electroactivity in the neutral solution through the examination of cyclic voltammetry and in-situ UV–vis adsorption spectra. The electroactivity is evidenced by anodic oxidation of ascorbic acid (AA). The larger anodic current and the smaller onset potential occur on PDMA films for anodic oxidation of AA relative to PANI films. This is because two electron donating groups (–OCH3) on PDMA significantly enhance the electrocatalytic activity. The behavior of methanol adsorption on platinum/poly(2,5-dimethoxyaniline) (Pt/PDMA) composite is investigated using UV–vis spectroscopy and open circuit potential (OCP). The results of scanning electron microscopy and energy dispersive spectroscopy are used to verify the uniform dispersion of Pt in PDMA. The Fourier transform infrared spectra and OCP results revealed that Pt particles interact with PDMA through the electron-rich nitrogen sites, influencing the oxidation state of PDMA. A model is proposed for the methanol adsorption on Pt particles which changes the interaction between Pt and PDMA. With the proposed model, methanol concentration can be discerned using potentiometric measurements. The results of this study can be applied to methanol sensors for direct methanol fuel cells. Cross-linking structural copolymer, poly(2,5-dimethoxyaniline-co- 2,5-diaminobenzenesulphonic acid) was synthesized by electrochemical deposition of two monomer, 2,5-dimethoxyaniline, DMA and 2,5-diaminobenzenesulfonic acid, DABSA. The cross-linking structure of copolymer was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and thermogravimetric techniques. Copolymer with cross-linking structure provides more and deeper nucleation sites for the deposition of platinum (Pt) than homopolymer via electrochemical method, being certified by secondary ion mass spectrometer. Meanwhile, the existence of the –SO3H group in copolymer might also help the electrodeposition of Pt. Pt/copolymer nanocomposite film demonstrates better activity and stability toward methanol oxidation than Pt/PDMA.