Synthesis of high-quality graphene by electrochemical anodic and cathodic co-exfoliation method

Large-scale preparation of high-quality graphene nanosheets at low cost is critical for advancing its industrial applications. Here we propose a fast electrochemical anode and cathode co-exfoliation method to synthesize high-yield solution-processable graphene. The chosen tetrabutylammonium hexafluorophosphate molecule, with superior electrochemical stability and oxygen-free feature, could efficiently enable simultaneous anion and cation intercalation while suppressing structural damage from anodic oxidation, resulting in minimally destructive exfoliation and high-efficiency graphene synthesis. After accurately regulating the intercalation chemistry, high-yield graphene (75% and 92% for anode and cathode, respectively) with uniform thickness distribution (>75%, 1-3 layers) was obtained. Meanwhile, as-prepared graphene has ultralow defect density (ID/ IG < 0.052), significantly high C/O ratio (>46.6) and exceptional electrical conductivity (>4 x 104 S m-1). Remarkably, record high production rates (over 100 g h-1) are achieved in up-scaled fabrication process, and such graphene quality and exfoliation efficiency outperform most previously reported research. Furthermore, the graphene based flexible supercapacitor exhibits a high area capacitance of 95 mF cm-2, excellent rate capability, cycling performance with 99% after 10,000 cycles and robust mechanical flexibility. This efficient and scalable process will promote the mass production of high-quality graphene, which offers great potential applications in wearable electronics.