In-situ etching-activation towards carbon bowl-like hemispheres for energy storage

Bowl-like hemisphere is an ideal choice to increase the packing density of carbonaceous materials for energy storage applications. However, there are few reports on the preparation of bowl-like carbon hemispheres (BCH) because of the complexity and particularity of their structures. Herein, we demonstrate that KNO3 can be applied into the in-situ etching-activation approach for the templating synthesis of BCH with controllable structures. Detailed experimental studies reveal that the structures in our system can be well adjusted by changing the amount of KNO3, realizing transformation from hollow spheres to hollow spheres with hole and then to bowl shape. The resultant BCH shows uniform open hemispherical structure, abundant nitrogen species, high surface area, and rich porous structure and, as a result, deliver high capability and rate capability for energy storage in supercapacitor. This facile in-situ etching-activation approach offers new opportunities in exploring sophisticated multimodal structures for innovative applications.