Electrochemical degradation of Nafion ionomer to functionalize carbon support for methanol electro-oxidation

Abstract

An effective electrochemical route to produce functional groups on carbon surface is demonstrated. Cyclic voltammetric (CV) sweeps are performed in 0.5 M H(2)SO(4) electrolyte on electrodes containing carbon cloth, Vulcan XC72R, and Nation ionomer. With supply of ambient oxygen, the generation of hydroxyl radicals from the oxygen reduction reaction during CV cycles initiates the decomposition of Nation ionomer that leads to formation of oxygenated functional groups on the carbon surface. Ion chromatography confirms the dissolution of sulfate anions upon CV scans. Raman analysis suggests a minor alteration for the carbon structure. However, X-ray photoelectron spectroscopy indicates a significant increase of oxygenated functional groups in conjunction with notable reduction in the fluorine content. The amount of the oxygenated functional groups is determined by curve fitting of C is spectra with known constituents. These functional groups can also be found by immersing the as-prepared electrode in a solution containing concentrated residues from Nation ionomer decomposition. The functionalized electrode allows a 170% increment of Pt ion adsorption as compared to the reference sample. After electrochemical reductions, the functionalized electrode reveals significant improvements in electrocatalytic abilities for methanol oxidation, which is attributed to the oxygenated functional groups that facilitates the oxidation of CO on Pt. (C) 2011 Elsevier B.V. All rights reserved.