Green and High-Efficiency Production of Graphene by Tannic Acid-Assisted Exfoliation of Graphite in Water

Abstract

A green and high-efficiency method was developed to prepare low-cost and high-quality graphene on a large scale through direct exfoliation of graphite in aqueous media using tannic acid (TA) as the stabilizer. The influence of preparation parameters on graphene concentration (C G ) and graphite exfoliation efficiency (C G /C G,i ), including TA concentration (C TA ), initial graphite concentration (C G,i ), pH, ionic strength, sonication time, and cycles, was systematically investigated. Under the optimum conditions, the highest C G that can be attained is 1.25 mg•mL −1 with C G /C G,i equal to 2.5%, and 92% of the as-formed graphene are few-layer graphene (below 5 layers) with the electrical conductivity as high as 488 S•cm −1 . Due to TA on the graphene surface acting as the dual roles of dispersant and interfacial regulator, the high-quality graphene can be uniformly dispersed and tightly integrated into polymer matrices for high-performance and multifunctional polymer nanocomposites. In a word, this contribution provides a simple, green, high-efficiency, and scalable avenue for mass production and utilization of highquality graphene.

SMA-Assisted Exfoliation of Graphite by Microfluidization for Efficient and Large-Scale Production of High-Quality Graphene

“…These values are appreciably greater than the theoretical thickness of monolayer graphene (0.334 nm) because of the attached SMA molecules on the surface and the folded structure of the material. Actually, similar observations are reported in other AFM studies [12,23,26]. Therefore, it could be concluded that the graphene produced by SMA-assisted microfluidization is mainly a few-layer (less than 5) structure with a lateral size of 0.5-0.9 μm, which is consistent with the TEM results.…”

“…The results presented in Figure 3b demonstrate that maximum values of C G are attained at C SMA = 10 mg·mL −1 , irrespective of the number of microfluidization cycles. A higher concentration of SMA will not promote further increase in C G because of the graphene surface that becomes saturated with adsorbed SMA molecules [23].…”

An alternative avenue for high‐performance phenolic resin/graphene composite

“…Although researchers have studied PR/graphene composites in detail, all the previous PR/graphene composites were maded of GO/rGO. Because of its structural defects, the properties of GO/rGO are far inferior to those of pristine graphene (pG) . Therefore, the performance of PR/graphene composites has much room for further improvement.…”

“…Therefore, the performance of PR/graphene composites has much room for further improvement. Even worse, as a large amount of highly corrosive acids, strong oxidizing reagents and toxic reductants are used in the preparation of GO/rGO, following a series of problems such as high explosion risk, serious environmental pollution, and complex technology, the production of GO/rGO is facing more and more severe challenges with the worldwide ever‐increasing awareness of safety, and environmental protection . On this background, methods of direct exfoliation of natural graphite for producing pG, such as liquid‐phase exfoliation method, ball‐milling method, and so forth, have developed rapidly for their advantages of simplicity, safety, environmental friendliness, and high productivity.…”

“…On this background, methods of direct exfoliation of natural graphite for producing pG, such as liquid‐phase exfoliation method, ball‐milling method, and so forth, have developed rapidly for their advantages of simplicity, safety, environmental friendliness, and high productivity. So far, the productivity of pG has exceeded that of GO/rGO . In comparison with GO/rGO, the low cost and good quality of pG make it more suitable as a nanofiller for preparing low‐cost, high‐performance, and multifunctional composites at present.…”