Surface chemical modifications induced on high surface area graphite and carbon nanofibers using different oxidation and functionalization treatments

Two graphitic carbon materials with different edge to basal plane ratio, high surface area graphite (HSAG) and graphitized carbon nanofibers (CNFs), were oxidized by two methods, aqueous-HNO3 wet oxidation and oxygen plasma oxidation. Characterization of the materials by temperature-programmed desorption, thermogravimetry and X-ray photoelectron and Raman spectroscopies indicated that the amount and nature of oxygen surface groups introduced depended on the oxidation method and on the structure of the original material. While surface sites within the layers were only oxidized by oxygen plasma, surface sites at the edges of graphene layers were oxidized by both treatments being the wet oxidation more effective. Modification of the oxidized materials with a diamine or a triamine molecule resulted in the formation of ammonium carboxylate salt species on the carbon surface.

The efficiency of the two oxidation treatments studied seems to depend on the morphology (edge to basal plane ratio) of the carbon material.Figure optionsDownload high-quality image (64 K)Download as PowerPoint slideResearch highlights
► Two carbon materials with different edge to basal plane ratio are oxidized by nitric acid or oxygen plasma.
► Wet oxidation attacks the C atoms at the edges and oxygen plasma is able to attack both C atoms at the edges and at the basal planes.
► Plasma oxidation seems more adequate for materials with lower edge to basal plane ratio as the CNFs.
► Modification of the oxidized materials with an amine molecule gives rise to materials probably holding ammonium carboxylate salt species.