Sustainable Synthesis of N,P-doped activated carbons from chitosan for superior supercapacitor performance

In this work, N,P-doped carbon materials were synthesized from an abundant biomass source (i.e. chitosan with different molecular weights) by using an easy synthetic protocol based on chemical activation with phosphoric acid and subsequent heat treatment. Chitosan-derived activated carbon exhibits a well-developed porous texture (S BET from 930 to 1515 m 2 g −1 ) and nitrogen and phosphorus contents of 2.33-3.33 at % and 0.40-0.56 at %, respectively. The presence of heteroatoms was maintained even after treatment at high temperatures (900 °C), which endow the activated carbon with unique electrochemical properties. The assessment of developed N,P-doped carbon materials as supercapacitor electrodes revealed that they exhibit a promising electrochemical performance. The best-performing supercapacitor (ACM_TT) displays an energy density of 18.2 Wh kg −1 and a capacity of 24 F g −1 with a remarkable capacitance retention value of 94 % after 10000 galvanostatic charge-discharge cycles, which is better than that of the supercapacitor based on an activated carbon used in commercial capacitors (YP-50F). The cornerstone of this work is the dual effect attained by both heteroatoms in the carbon matrix, which together with the straightforward and sustainable approach of the study makes the developed chitosan-derived activated carbons excellent candidates for energy storage devices.