Facile Surface Functionalization of Carbon/Nafion for Enhancement of Methanol Electro-Oxidation

Yu-Chi Hsieh, Li-Chung Chang, Pu-Wei Wu, Jyh-Fu Lee, Chen-Hong Liao
2010 unpublished
We report a facile electrochemical method to produce functional groups on the carbon surface in which multiple cyclic voltammetric (CV) sweeps are imposed in 0.5 M H 2 SO 4 electrolyte on the samples containing carbon cloth, Vulcan XC72R, and Nafion ionomer. With supply of ambient O 2 , the generation of radicals from the oxygen reduction and Nafion ionomer degradation enables an accelerated formation of oxygenated functional groups on the carbon surface. Raman analysis reveals structural
more » ... ls structural variation for the carbon electrodes after CV modifications. X-ray photoelectron spectroscopy confirms the alteration of carbon structure in conjunction with notable increase of oxygenated groups and reduction in fluorine amount. The functionalized electrodes allow a 250% increment for PtRu electrodeposition as compared to the reference sample. We carry out electrochemical measurements on methanol electro-oxidation for the PtRu samples. The functionalized electrode demonstrates significant improvement in apparent current density and mass activity as opposed to the reference sample. Carbon is widely used as the electrode support for various electrochemical applications. Unfortunately, the untreated carbon is often hydrophobic that allows limited adsorption of catalyst precursors and catalysts. Therefore, it is of particular interest to carry out additional functionalization treatments on the carbon surface to render a hydrophilic surface instead. Moreover, it is expected that the oxidized functional groups on carbon supports lead to an increased Pt loading and promote methanol electrooxidation (MOR) (1, 2). Conventional carbon functionalization involves tedious treatments in acidic solution at elevated tempeature. It is suggested that the Nafion ionomer could possibly be decomposed with the formation of functional groups that attach themselves onto the carbon support. Previously, responsible mechanisms for Nafion membrane degradation have been studied in polymer membrane fuel cells (3). However, the decomposition of Nafion ionomer and the resulting species have not been investigated carefully. In this work, we impose deliberate electrochemical decompositions of Nafion ionomer and evaluate their effects on the carbon supports for PtRu deposition and MOR activities.
doi:10.1149/1.3484693 fatcat:7dlo6b3debeftn2pyjawguegeu