Electrochemical Synthesis of Co-intercalation Compounds in the Graphite-H2SO4-H3PO4System

Abstract

Anodic oxidation of highly oriented pyrolytic graphite in an electrolyte containing concentrated sulfuric and anhydrous phosphoric acids is studied for the first time. The synthesis was carried out under galvanostatic conditions at a current I = 0.5 mA and an elevated temperature ( t = 80° C). Intercalation compounds of graphite (ICG) are shown to form at all concentration ratios of H 2 SO 4 and H 3 PO 4 acids. The intercalation compound of step I forms in solutions containing more than 80 wt % H 2 SO 4 , a mixture of compounds of intercalation steps I and II forms in 60% H 2 SO 4 , intercalation step II is realized in the sulfuric acid concentration range from 10 to 40%, and a mixture of compounds of intercalation steps III and II is formed in 5% H 2 SO 4 solutions. The threshold concentration of H 2 SO 4 intercalation is ~2%. With the decrease in active intercalate (H 2 SO 4 ) concentration, the charging curves are gradually smoothed, the intercalation step number increases, and the potentials of ICG formation also increase. As the sulfuric acid concentration in the electrolyte changes from 96 to 40 wt %, the filled-layer thickness d i in ICG monotonously increases from 0.803 to 0.820 nm, which apparently is associated with the greater size of phosphoric acid molecules. With further increase in H 3 PO 4 concentration in solution, d i remains unchanged. According to the results of chemical analysis, both acids are simultaneously incorporated into the graphite interplanar spacing and their ratio in ICG is determined by the electrolyte composition.

A dehydration and stabilizer-free approach to production of stable water dispersions of graphene nanosheets

“…In this work, H 2 SO 4 or H 3 PO 4 not only served as the dehydrating reagent, but also as the intercalating reagent that was particularly important for preventing GS from aggregating during the dehydration process. 21 Replacing H 2 SO 4 or H 3 PO 4 by HCl or HNO 3 gave negligible change of the dispersion in absorption spectra and color, suggesting that the dehydration property of H 2 SO 4 or H 3 PO 4 was responsible for the chemical conversion of GO to GS (Fig. S2 †).…”

Preparation of Expandable Graphite Intercalated by Sulfuric Acid and Sodium Silicate and Its Flame Retardancy Application for Ethylene Vinyl Acetate Copolymer

“…However, the use of it leads to high sulfur content in products and corrosion of storage devices caused by lixiviating vitriol. So, it is necessary to supplement assistant intercalating agent to replace part of H2SO4 15,16 . The most remarkable thing is that if a traditional flame retardant is used as assistant intercalating agent, it is not only can decrease sulfur content in graphite intercalation substances, but also improve its flame retardant property.…”