Concomitant Thionation and Reduction of Graphene Oxide Through Solid/Gas Metathetical Sulfidation Reactions at High Temperatures

We show that thionation of graphene oxide sheets is possible concomitantly with reduction of graphene oxide through a high-temperature (up to 500°C) solid/gas metathetical reaction process by employing gaseous boron sulfides as a thionation reagent which can effectively prevent the graphene oxide sheets from restacking during the heating. The X-ray photoelectron (XPS) and energy dispersive X-ray (EDS) spectroscopic studies revealed that reaction products have the S:O atomic ratios of about 2:1. The deconvolution of the high-resolution S2p XPS spectra of the product showed that about 90% of the sulfur atoms in the products are present in the form of C-SH. Ellman assay results indicated that practically all the thiols act as a free thiol which can participate in disulfide bond formation. From the thermogravimetric analysis (TGA) studies up to 600°C, the thiol functional groups in the products was found to be more thermally stable than hydroxyl groups. The estimated Tauc optical gap of the products is about 0.03 eV, which corroborates the reduced nature of the products.