Ding Zheyuan, Mei Xiuwen, Wang Xiluan
Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University Beijing 100083 P. R. China
Nanoscale Adv. 2021 Mar 5;3(9):2529-2537. doi: 10.1039/d0na01024c. eCollection 2021 May 4.
The high value-added conversion of biomass lignin has been paramount in the field of lignin utilization, especially for high performance energy conversion and storage devices. A majority of lignin-based supercapacitors generally exhibit inferior electrochemical performance with low capacitance and slow diffusion kinetics due to the poor interfacial compatibility, low conductivity, and uncontrollable morphology. Herein, we designed all-lignin converted graphene quantum dot and graphene sheet (GQD/Gr) hetero-junction for simultaneous fast charging and boosted specific capacitance. The conversion from lignin to GQDs and then refusion into graphene allows the growth of GQDs on graphene, endowing good interfacial compatibility with the GQD/Gr hetero-junction. Furthermore, both GQDs and graphene sheets exhibit highly crystalline structure with obvious graphene lattice, giving GQDs/Gr good conductivity. GQDs play an additive role for avoiding stacks and agglomerates between graphene layers, which endow the assembled GQDs/Gr with massive electron capacitive sites and more hierarchical channels. Therefore, the GQD/Gr hetero-junction gives rise to a high specific capacitance of 404.6 F g and a short charging time constant ( ) of 0.3 s, 2.5 times higher and 7.5 times faster than that of the unmodified lignin electrode with 162 F g and 2.3 s, respectively. This proposed strategy could offer the opportunity to unblock the critical roadblocks for a superior electrochemical performance lignin-based supercapacitor by composing a 0D/2D GQD/Gr hetero-junction system and also paves a bright way for the high-value industrial lignin conversion into cheap, scalable, and high-performance electrochemical energy devices.
生物质木质素的高附加值转化在木质素利用领域至关重要，特别是对于高性能能量转换和存储设备而言。由于界面相容性差、导电性低和形态不可控，大多数基于木质素的超级电容器通常表现出较差的电化学性能，电容低且扩散动力学缓慢。在此，我们设计了全木质素转化的石墨烯量子点和石墨烯片（GQD/Gr）异质结，以实现同时快速充电和提高比电容。从木质素到石墨烯量子点的转化，然后再融合到石墨烯中，使得石墨烯量子点在石墨烯上生长，赋予了GQD/Gr异质结良好的界面相容性。此外，石墨烯量子点和石墨烯片都表现出具有明显石墨烯晶格的高度结晶结构，赋予GQDs/Gr良好的导电性。石墨烯量子点起到了避免石墨烯层之间堆叠和团聚的添加剂作用，这赋予组装后的GQDs/Gr大量的电子电容位点和更多的分级通道。因此，GQD/Gr异质结产生了404.6 F g的高比电容和0.3 s的短充电时间常数（ ），分别比具有162 F g和2.3 s的未改性木质素电极高2.5倍和快7.5倍。这种提出的策略可以通过构建0D/2D GQD/Gr异质结系统，为克服基于木质素的超级电容器优异电化学性能的关键障碍提供机会，也为将高价值工业木质素转化为廉价、可扩展和高性能的电化学能量设备铺平了光明的道路。
