Application Of G-C₃N₄ In Supercapacitors

With the excessive development and consumption of energy,exploring a clean,efficient and ecofriendly energy source has become increasingly important.Supercapacitors,a high-performance energy storage device,have attracted increasing attention because of their fast charge-discharge rates,high energy and power density and long cycle life.Based on the difference in the energy storage mechanism,a supercapacitor can be divided into an electric double layer capacitor?EDLC?and a pseudocapacitor.The EDLC stores energy through the adsorption and release of ions between the electrolyte and electrode material,which are composed of C materials such as activated carbon,carbon nanotubes and graphene.Pseudocapacitors store energy through fast reversible faradaic reactions on the surface of electrode materials,which are composed of conducting polymers and metal oxides such as RuO₂ and MnO₂.G-C₃N₄?CN?,a two-dimensional?2D?graphite-like structure,has attracted increasing attention because of its high nitrogen content,which can provide more active reaction sites and additional electrons to enhance conductivity and improve wettability with electrolytes.Usually,there are two methods to address g-C₃N₄ for supercapacitors,g-C₃N₄ is oxidized through a treatment with concentrated acid,and oxidized g-C₃N₄?OCN?possesses abundant oxygen-containing functional groups,such as hydroxyl and carboxyl groups that allows the metal oxide to be loaded onto the oxidized CN for supercapacitors.The second method of processing is to use various methods to peel off CN to obtain CN nanosheets and apply them to supercapacitors.?1?g-C₃N₄ is oxidized through a treatment of concentrated nitric acid.The oxidation treatment of g-C₃N₄ through concentrated nitric acid successfully cuts the large layered g-C₃N₄ to smaller segments that have a large surface area,which not only increases the edge nitrogen atoms of g-C₃N₄ but also introduces many oxygen functional groups that increase the electrostatic interaction between the Fe³⁺and oxygen-containing groups in g-C₃N₄.The composite with 10%Fe₂O₃ nanospheres coupled with the oxidized g-C₃N₄ exhibits an electrochemical performance with an excellent specific capacitance of 243 F g^-1,which is better than that of pure Fe₂O₃.Moreover,the 10%Fe₂O₃/OCN exhibits excellent cycling performance after 1000 cycles.?2?Graphitic carbon nitride?g-C₃N₄?nanosheets were synthetized by chemical oxidation method and thermal oxidation method.The properties of the prepared g-C₃N₄ nanosheets were analyzed using TEM,XRD,FTIR and their electrochemical performance were further investigated using cyclic voltammetry?CV?,electrochemical impedance spectrometry?EIS?,and chronopotentiometry?GCD?.The g-C₃N₄,the g-C₃N₄ after chemical oxidation and the g-C₃N₄ after thermal oxidation show different electrochemical properties.More importantly,the specific capacitance of g-C₃N₄ nanosheets after thermal oxidation of 580°C(170.1 F g^-1)is higher than CN(127.7 F g^-1)and g-C₃N₄ after 12M sulfuric acid(133.6 F g^-1)at a current density of 0.5 A g^-1.And an excellent cyclic stability was obtained with a capacity retention of approximately 95.9%after 1000 cycles in a 2M KOH solution.Further,g-C₃N₄nanosheets after thermal oxidation of 580°C show good energy density of 3.740wh/kg and power density of 99.46w/kg characteristics superior application potential for high performance energy storage devices.