Electrochemical Polymerization of a Novel Thiophene-Derived Monomer and Its Use as Support Material for Methanol Oxidation

Abstract

This research, conductive polymer supported modified electrode system which was prepared for usage in direct methanol fuel cells. To test the behavior of these electrode system for methanol oxidation, cyclic voltammetry (CV), chronoamperometry (CHR) and electrochemical impedance spectroscopy (EIS) methods were used as electrochemical methods. As the working electrode, pencil graphite electrode (PGE) was preferred because of its porous structure, good ion conductivity, practicality in application and ease of preparation and obtaining. Thiophene derivative 4,4')-2,2'-(diazen-1,2 diylbis(4,1 phenylene))bis(4 (thiophene-2-ylmethylene) oxazol-5(4H)-one), (DiAzBiPhBiTyOx) monomer was prepared and electrochemically polymerized by CV method in 0.01M TBAP and 0.05 HClO4 containing ACN solution on the surfaces of PGE. The spectroscopic characterization of the synthesized monomer was performed by NMR spectroscopy. Optimum polymerization conditions of monomer was determined according to scanning rate, potential range and acid density. The obtained modified electrode system (PGE/PDiAzBiPhBiTyOx) was doped with chloroplatinic acid hexahydrat-Pt2Cl6.6H2O (Pt) at different densities and the optimum catalyst density was determined as 3.25mM (PGE/3.25mMPt@PDiAzBiPhBiTyOx). The methanol oxidation performances of conductive polymer film, platinum and conductive polymer supported platinum catalyst systems were investigated separately. While the methanol oxidation responses of the conductive polymer film and platinum are almost similar, the methanol oxidation response of the platinum doped conductive polymer film catalyst system is higher. The modified electrode characterization was performed by CV, CHR and EIS methods. Furtheremore obtained modified electrode systems were characterized by FESEM/EDS, XRD to confirm the structures and morphologies. Also, the theoretical values such as electrochemical surface area (ECSA) and specific capacitance (Cs) were calculated in aqueous acidic solution with and without methanol. Cs values of the PGE/3.25mMPt@PDiAzBiPhBiTyOx electrode in aqueous acidic solution with and without methanol were 3.861 and 3x10-4Fg-1 respectively. Also, the electrochemical surface area values of the same electrode in aqueous acidic solution with and without methanol were 196.437 and 21.150m2g-1 respectively.