Hydrophilization of graphite using plasma above/in a solution

Abstract

A hydrophilization method for graphite is required for applications such as conductive ink. In typical chemical oxidation methods for graphite have the problems of producing many defects in graphite and a large environmental impact. In recent years, the plasma treatment has attracted attention because of the high quality of the treated samples and the low environmental impact. In this study, we proposed an above-solution plasma treatment with a high contact probability of graphite and plasma since graphite accumulates on the solution surface due to its hydrophobicity, which we compared with a so-called solution plasma treatment. Graphite was hydrophilized via reactions with OH radicals generated by the plasma. It was confirmed that hydroxyl and carboxyl groups were modified to the graphite and the dispersibility was improved. The above-solution plasma achieved more energy-efficient hydrophilization than the solution plasma and it was possible to enhance the dispersibility by increasing the plasma-solution contact area.

Investigation of the sulfonation mechanism by gas–liquid interfacial plasma under atmospheric pressure conditions

“…Similar to the mechanism of hydrophilic modification via OH radicals generated by the plasma-water interaction (reported by Hoshino et al) [12], we speculate that certain active species would be generated when plasma interacts with H 2 SO 4 solution in the plasma sulfonation process, which would eventually graft on the carbon surface to produce acid functional groups. To prove our hypothesis, we developed a gas-liquid interfacial plasma sulfonation system similar to that reported by Qin et al under atmospheric pressure conditions, where the radicals and gas compositions generated by the plasma process were characterized by OES and Fourier transform infrared spectroscopy (FTIR).…”

“…Andreas and Kim et al found that low-pressure SO 2 /O 2 plasma treatment is a simple method of producing a polymer with a high concentration of acidic groups (sulfonic acid and hydrogen sulfate) [9,10], and the reactive particles created in the non-equilibrium plasma modification under a low-pressure atmosphere were confirmed as SO, S, and O radicals by optical emission spectroscopy (OES) [11]. Hoshino et al added hydroxyl and carboxyl groups to modify graphite hydrophilicity via in-solution and abovesolution plasma processes [12]. Based on this study, graphite hydrophilization using the plasma process was created by the reaction between the graphite surface and OH radicals produced via the interaction of plasma with H 2 O.…”

Mechanochemical Functionalization of Carbon Black at Room Temperature

“…On the other hand, milder methods like plasma treatment are also commonly applied. In this way, carbon nanotubes, graphite, and porous carbons are surface functionalized, either by O2 plasma [20], above-solution plasma [21], or Ar plasma [22], respectively. Nevertheless, plasma treatment also exhibits environmental issues as a result of the high power input and the extensive technical equipment required.…”

Green Oxidation of Carbon Black by Dry Ball Milling

“…Moreover, plasma treatment , might also be an alternative to perform the reaction in milder conditions, but advanced equipment and high power input are again incompatible with the environmental concerns.…”

“…28 Furthermore, the energy required to produce ozone in all cases and even more on gasified carbon black reduces the energy efficiency metric increasing the energy demand required for the process. Moreover, plasma treatment 32,33 might also be an alternative to perform the reaction in milder conditions, but advanced equipment and high power input are again incompatible with the environmental concerns.…”