Large-scale and clean preparation of low-defect few-layered graphene from commercial graphite via hydroxyl radical exfoliation in an acidic medium

Graphene has been verified as one of the most promising nanomaterials for an extensive range of applications, and large-scale, clean and cost-effective preparation of low-defect graphene is still a major challenge both in academia and industry until now. In this work, a novel hydroxyl radical exfoliation method of commercial graphite into graphene at the kg scale for each run was achieved in an acidic medium in the presence of potassium formate and polyaspartic acid solution serving as an electrical conductor and exfoliation assistant. Then, a systematic investigation was conducted to explore the optimal crucial parameters with respect to the exfoliation efficiency of the proposed technology and the quality evaluation of the resulting graphene products. At the optimal process parameters, in which the applied current density was 0.056 A m−2, the air flow rate was 1.0 L min−1, the mass ratio of potassium formate, polyaspartic acid and water was 30 : 9 : 61, the mass ratio of the binary assistant solution to graphite was 10 : 3 and the exfoliation time was 3 h, the highest yield of the graphene product reached 98.2%. Furthermore, the prepared graphene product has quite low defects and the percentage of 2-layer graphene in the product was as high as 92%. The graphene preparation process is clean and operated at room temperature, with only air and electricity consumption, and the binary components solution recycling usage, and without any aggressive agents employed and the graphite and the assistants used were all industrially available. Therefore, this cost-effective strategy is practically promising for large-scale preparation of higher quality graphene from low-cost commercial graphite.