Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA.
Department of Materials Science and Engineering, UCLA, Los Angeles, CA, 90095, USA.
Adv Mater. 2018 Feb;30(8). doi: 10.1002/adma.201704449. Epub 2018 Jan 10.
A facile method to convert biomolecule-based carbon nanodots (CNDs) into high-surface-area 3D-graphene networks with excellent electrochemical properties is presented. Initially, CNDs are synthesized by microwave-assisted thermolysis of citric acid and urea according to previously published protocols. Next, the CNDs are annealed up to 400 °C in a tube furnace in an oxygen-free environment. Finally, films of the thermolyzed CNDs are converted into open porous 3D turbostratic graphene (3D-ts-graphene) networks by irradiation with an infrared laser. Based upon characterizations using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman spectroscopy, a feasible reaction mechanism for both the thermolysis of the CNDs and the subsequent laser conversion into 3D-ts-graphene is presented. The 3D-ts-graphene networks show excellent morphological properties, such as a hierarchical porous structure and a high surface area, as well as promising electrochemical properties. For example, nearly ideal capacitive behavior with a volumetric capacitance of 27.5 mF L is achieved at a current density of 560 A L , which corresponds to an energy density of 24.1 mWh L at a power density of 711 W L . Remarkable is the extremely fast charge-discharge cycling rate with a time constant of 3.44 ms.
提出了一种将基于生物分子的碳纳米点（CND）转化为具有优异电化学性能的高表面积 3D 石墨烯网络的简便方法。首先，根据先前发表的方案，通过微波辅助热解柠檬酸和尿素合成 CND。接下来，将 CND 在管式炉中于无氧环境下在 400°C 下退火。最后，通过用红外激光辐照，将热解 CND 的薄膜转化为开放多孔 3D 乱层石墨烯（3D-ts-石墨烯）网络。通过扫描电子显微镜、透射电子显微镜、X 射线光电子能谱、X 射线衍射、傅里叶变换红外光谱和拉曼光谱的表征，提出了 CND 的热解和随后的激光转化为 3D-ts-石墨烯的可行反应机制。3D-ts-石墨烯网络具有优异的形态特性，如分层多孔结构和高表面积，以及有前途的电化学性能。例如，在电流密度为 560 A L 时，实现了近理想的电容行为，体积电容为 27.5 mF L ，相应的能量密度为 24.1 mWh L 在功率密度为 711 W L 时。值得注意的是，其具有非常快的充放电循环速率，时间常数为 3.44 ms。
