Process In Preparation Of Graphene By High Gravity Oxidation-Reduction Method

Graphene, a single sheet of carbon atomstightly arranged in a two-dimensional (2D) honeycomb lattice, has attracted enormous attention from both the basic experimental research and technical application due to its outstanding mechanical, thermal, optical and electronic properties arising from its strictly 2D structure. These properties possess a series of potential applications in many different areas such as sensors, supercapacitors, solar cell and so on. For further applications, there is a big challenge for chemists to develop new effective and scalable approaches to prepare graphene.This work reports the preparation of graphene by high gravity rotating packed bed (RPB) and investigates influent factors during the preparation, then establishes greater efficiency, better control and scale-up method to synthesis high quality graphene. In addition, the common method which exfoliated by sonication and reduced by stirred tank reactor is compared with high gravity method, the research results are listed as follows:(1) The packing volume fraction is the most obvious factor for the as-prepared graphene oxide in the exfoliation process, next is exfoliated time, concentration of GO solutions and rotor speed, respectively. A large double-layer graphene oxide can be obtained according to optimum conditions, its layer area is over 6 um2 and specific surface area is about 735 m2·g-1, the concentration of GO solutions can reach 1.5 mg·mL-1 which is far higher than the concentration exfoliated by sonication method that range is 0.1～1.0 mg·mL-1. However, the specific surface area of graphene oxide can be increased 15% through adding surfactant or using RPB-sonication combined method.(2) In the reduction process of graphene oxide, the effects of reaction temperature, reduction time and reluctant on morphology, reduction degree and electrochemical property is studied emphatically. By analyzing the results, the reduction time under high gravity method is at least 50% shorter than common mechanical stirring method, reaction temperature and dosage of reducing agent also decreases 15% and 35%, respectively. The specific capacitance of as-prepared graphene by hydrazine can reach 247 F·g-1 and the graphene by ascorbic acid also has about 220 F·g-1.(3) Through analyzing the property of as-prepared products by high gravity and common sonication-mechanical stirring combination method, the specific surface area of graphene oxide by high gravity method is over ten times larger than common method in the same condition, and the thickness is only half of it. The capacitance and retention of graphene by RPB are improved 20%, the electrical conductivity is also increased 30%, respectively.RPB not only can promote the preparation efficiency and property of graphene based on it better control shear and intensified mass-transfer action, but it is also easily scaled up in industrial production.