Controlled Size Nano-Polypyrrole Synthetized in Micro-Emulsions as Pt Support for the Ethanol Electro-Oxidation Reaction

摘要

Polypyrrole (PPy) nanoparticles were synthesized by chemical polymerization in a microemulsionsystem based on water, nentanol and sodium dodecyl sulfate (SDS) as surfactant, using pyrrolemonomer and ferric chloride (FeCl3) as oxidizing agent. Additionally, PPy-fibers were obtained byadding necane to the polymerization system. PPy structures were characterized by scanning electronmicroscopy (SEM). Fourier transform infrared spectroscopy (FTIR) analysis demonstrated thatpolymerization in microemulsion prevented the formation of a carbonyl function associated withoveroxidation of polymer chains. The presence of dodecylsulfate as doping agent was confirmed bythe S=O asymmetric stretching band in PPy-nanoparticles and PPy-fibers, while sulfur concentrationdetermined by energy-dispersive X-ray spectroscopy (EDX) can be related to the PPy doping level.The PPy-nanoparticles conductivity was higher than that of other PPy tested materials tested. This isattributed to the doping agent nature and the structure of the polymer chains. Electrocatalysts of Ptsupported on the PPy structures were obtained by reduction of H2PtCl6 by means of a NaBH4 solution.Electrochemical measurements were performed in a three-electrode cell. Cyclic voltammetry resultsfrom these Pt/PPy catalysts, showed the characteristic peaks of ethanol electro-oxidation. Pt/PPy- nanoparticles presented lower charge transfer resistance (Rct) than a Pt/C catalyst. Ethanol electro- oxidation on Pt was enhanced by using nanostructured PPy as support. The PPy-nanoparticles showedbetter structural, conducting and electrochemical activity properties than other PPy synthesizedmaterials tested as catalyst supports.