Promising Nitrogen-Rich Porous Carbons Derived from One-Step Calcium Chloride Activation of Biomass-Based Waste for High Performance Supercapacitors

It has long been demonstrated that KOH and ZnCl2 can be used as efficient chemical activation agents to prepare porous carbons. Herein, we develop a green activation method, that is, one-step calcium chloride (CaCl2) activation sugar cane bagasse with urea, for the preparation of nitrogen-rich porous carbons (NPCs). The nitrogen contents, specific surface areas, pore sizes, and specific capacitances of the obtained NPCs can be effectively tuned by adjusting the ratio of carbon precursor (sugar cane bagasse), nitrogen source (urea), and activation agent (CaCl2). The synthesized three-dimensional oriented and interlinked porous nitrogen-rich carbons (3D-NPCs) contain not only abundant porosities which can impose an advantage for ion buffering and accommodation, but also high nitrogen content in the carbons which can obviously increase the pseudocapacitance. Therefore, for the typical sample, obtained from pyrolysis of the mixture of sugar cane bagasse, urea, and CaCl2 in a mass ratio of 1:2:2 at 800 °C for 2 h under N2 atmosphere, shows a high specific capacitance, excellent rate capability (with 323 and 213 F g–1 at the discharge/charge current densities of 1 and 30 A g–1, respectively), and outstanding cycle performance (a negligible capacitance loss after 10 000 cycles at 5 A g–1).