Top‐down thickness reduction synthesis of biomass‐derived carbon nanosheets with hierarchical pore structure for high‐performance supercapacitors

Carbon electrode materials with superior rate performance are highly demanded in application scenarios of high power output/input, especially when paired with organic electrolyte for extended voltage window and high energy storage. By extracting thin sheets of entangled cellulose fibers from cell wall structures, porous carbon nanosheets as templated from the cellulose sheets are synthesized. Evident thickness reduction effect has been demonstrated with thickness reduced from several micrometers to several nanometers of the obtained thickness‐reduced activated carbon nanosheets (TRAC), which endow the material with a large surface area and high pore volume. The obtained TRAC exhibits significantly enhanced ion diffusion kinetics and superior rate capability thanks to the shortened diffusion pathway and suitable pore size distribution. Effects of sonication time have also been investigated, showing a trade‐off between ion diffusion kinetics and pseudocapacitive contribution. This thickness‐reduction method is extendable to many other biomass sources as cellulose sheets are widely existed in nature, offering a practical and easy‐to‐implement strategy of fabricating porous carbon nanostructures for efficient energy storage and utilization.