Tailoring nitrogen-rich C₃N₅ nanosheets as a potential electrode material for high-performance supercapacitor

Carbon nitride has recently transpired as the inevitable two-dimensional polymeric layered material tailoring in various fields due to its chemical stability and tunable band gap. Herein, the facile and scalable synthesis through the thermal polymerization of 3-amino-1,2,4-triazole precursor serendipitously forms another stable allotrope, C₃N₅. An ultrathin C₃N₅ nanosheet was fortuitously achieved through the protonation process. Because of its electron-rich character and delamination of the stacked interlayer, the hydrochloric acid-treated C₃N₅ is endowed with ultra-high capacitance and impressive cyclic stability, outperforming the other carbon and metal oxide-based materials. As a result, it attains a high specific capacitance of 875 F/g, which is eight-fold higher than the pristine C₃N₅ and other acid-treated C₃N₅. It also displayed excellent cyclic stability of 100% over 10,000 cycles. Furthermore, the fabricated symmetric device demonstrated remarkable power and energy densities of 480 W/kg and 18 Wh/kg, respectively, with excellent cyclic stability of 90% over 5000 cycles. The rate capability and improved capacitance of hydrochloric acid-treated C₃N₅ are due to the effective construction of charged ions from the synergistically interplayed effect of segregated stacked interlayers with their strong in-planar heptazine unit of electron-rich nitrogen moieties. Additionally, ex situ Raman and SEM investigations were also performed, highlighting the CN heterocyclic unit robust structural packing even after the cycling mechanism. This will be an archetype for future sustainable development with commendable electrochemical properties as a resurgence to meet global energy demand.