High-concentration graphene dispersions prepared via exfoliation of graphite in PVA/H2O green solvent system using high-shear forces

Herein, an efficient, facile, scalable production of graphene dispersions via exfoliation of graphite in an environment-friendly PVA/H2O solvent system is reported. To warrant the impact of processing parameters on exfoliation efficiency, a systematic investigation is carried out using UV–visible spectroscopy. Under the optimal shearing parameters (1 h, 10 k rpm) with the PVA-to-fed graphite mass ratio of 10, a high concentration graphene dispersion (3.36 mg mL−1) is achieved. The estimated graphene yield is found to be 33% that further increases to 90% after sediment recycling. With the aim of detailed quality analysis, centrifugal cascading is adopted to predominately sort the graphene flakes from the upper end of the distribution. Through various characterization techniques, it is confirmed that the resulting dispersion comprises high-quality graphene flakes (1–5 layers) having thickness up to 1.48 nm, lateral dimension ranging from 0.3 to 4 µm, and quite a low level of defects (ID/IG = 0.1). The statistical distribution histogram reveals that most flakes are single-layer (41%), including some bi-layer (21%) and tri-layer (28%), while the remaining can be said five or multi-layer graphene. Meanwhile, the efficacy of the PVA/H2O solvent system is also demonstrated using ultrasonic exfoliation, providing a high concentration of graphene (1.1 mg mL−1) in a relatively short time (8 h). Furthermore, the applicability of the PVA-stabilized graphene dispersion is addressed by fabricating various graphene products such as graphene paper electrodes, graphene composites, and graphene thin films. Impressively, the graphene paper electrode imparts an exceptionally high specific capacitance of 199.63 F g−1 in a potential window range of 0 to 2 V, and hence could be a promising alternative to traditional electrodes in supercapacitors. Conclusively, the exfoliation of graphite in a green polymer–solvent system offers to produce highly concentrated graphene dispersions at a minimal cost that could be widely applicable in different research areas, thus holding the potential for commercial viability.