Mei Jing, Qiu Zhian, Gao Teng, Wu Qiang, Zheng Fenghua, Jiang Juantao, Liu Kui, Huang Youguo, Wang Hongqiang, Li Qingyu
School of Chemistry and Pharmaceutical Sciences, Guangxi Key Laboratory of Low Carbon Energy Materials, Guangxi Scientific and Technological Achievements Transformation Pilot Research Base of Electrochemical Energy Materials and Devices, Guangxi Normal University, Guilin, 541004, China.
Langmuir. 2023 Mar 28;39(12):4413-4426. doi: 10.1021/acs.langmuir.3c00046. Epub 2023 Mar 15.
Electrochemical exfoliation starting with graphite powder as the raw material for graphene production shows superiority in cost effectiveness over the popular bulk graphite. However, the crucial conductive network inside the graphite powder electrode along with its formation and influence mechanisms remains blank. Here, an adjustable-pressure graphite powder electrode with a sandwich structure was designed for this. Appropriate encapsulation pressure is necessary and conducive to constructing a continuous and stable conductive network, but overloaded encapsulation pressure is detrimental to the exfoliation and graphene quality. With an initial encapsulation pressure (IEP) of 4 kPa, the graphite powders expand rapidly to a final stable expansion pressure of 49 kPa with a final graphene yield of 46.3%, where 84% of the graphene sheets are less than 4 layers with / values between 0.22 and 1.24. Increasing the IEP to 52 kPa, the expansion pressure increases to 73 kPa, but the graphene yield decreases to 39.3% with a worse graphene quality including higher layers and / values of 1.68-2.13. In addition, small-size graphite powders are not suitable for the electrochemical exfoliation. With the particle size decreasing from 50 to 325 mesh, the graphene yield decreases almost linearly from 46.3% to 5.5%. Conductive network and electrolyte migration synergize and constrain each other, codetermining the electrochemical exfoliation. Within an encapsulated structure, the electrochemical exfoliation of the graphite powder electrode proceeds from the outside to the inside. The insights revealed here will provide direction for further development of electrochemical exfoliation of graphite powder to produce graphene.
以石墨粉为原料生产石墨烯的电化学剥离法在成本效益方面比常用的块状石墨更具优势。然而，石墨粉电极内部关键的导电网络及其形成和影响机制仍不清楚。在此，为此设计了一种具有三明治结构的可调压石墨粉电极。适当的封装压力是必要的，有利于构建连续稳定的导电网络，但过载的封装压力不利于剥离和石墨烯质量。初始封装压力（IEP）为4 kPa时，石墨粉迅速膨胀至最终稳定膨胀压力49 kPa，最终石墨烯产率为46.3%，其中84%的石墨烯片层小于4层，I值在0.22至1.24之间。将IEP提高到52 kPa，膨胀压力增加到73 kPa，但石墨烯产率降至39.3%，石墨烯质量变差，包括层数增加，I值为1.68 - 2.13。此外，小尺寸石墨粉不适合电化学剥离。随着粒径从50目减小到325目，石墨烯产率几乎呈线性从46.3%降至5.5%。导电网络和电解质迁移相互协同并相互制约，共同决定电化学剥离过程。在封装结构内，石墨粉电极的电化学剥离从外部向内部进行。这里揭示的见解将为进一步发展石墨粉电化学剥离制备石墨烯提供方向。
