Characterization of oxygen containing functional groups on carbon materials with oxygen K-edge X-ray absorption near edge structure spectroscopy

Abstract

Surface functional groups on carbon materials are critical to their surface properties and related applications. Many characterization techniques have been used to identify and quantify the surface functional groups, but none is completely satisfactory especially for quantification. In this work, we used oxygen K-edge X-ray absorption near edge structure (XANES) spectroscopy to identify and quantify the oxygen containing surface functional groups on carbon materials. XANES spectra were collected in fluorescence yield mode to minimize charging effect due to poor sample conductivity which can potentially distort XANES spectra. The surface functional groups are grouped into three types, namely carboxyl-type, carbonyl-type, and hydroxyl-type. XANES spectra of the same type are very similar while spectra of different types are significantly different. Two activated carbon samples were analyzed by XANES. The total oxygen contents of the samples were estimated from the edge step of their XANES spectra, and the identity and abundance of different functional groups were determined by fitting of the sample XANES spectrum to a linear combination of spectra of the reference compounds. It is concluded that oxygen K-edge XANES spectroscopy is a reliable characterization technique for the identification and quantification of surface functional groups on carbon materials.