Utilizing 2D Graphite Carbon Nitride for Industrial Applications – from Supercapacitors to Biosensors

Abstract

2D materials are slowly overcoming the critical drawbacks of stability, low conductivity, reproducibility and cost. Therefore, with their intrinsic advantages of: ultra-large specific surface areas, well-defined layered architecture, tuneable redox activity and material hybridization, many 2D materials beyond graphene are being discovered. Few such 2-D materials, which have been reported are WS2, MoS2, h-BN, etc. Recently, 2D nano-sized graphite carbon nitride (g-C3N4) has been reported, with prediction that it can become an excellent candidate for miniaturized energy storage and optoelectronic devices. Graphite carbon nitride is a 2-D layered structure, where the tris-triazine unit are connected with planner amino groups in each layer, and weak van der Waal force acts between the layers. The quantum size effect are quite prominent along the inplane direction, which leads to interesting modulations in electrical and chemical properties. The nitrogen functional groups-rich frame-work is also expected to synergistically contribute in enhancing the electrochemical response of the material. Large synthesis of this material has remained a challenging task.In this paper, using a low-cost pyrolysis synthesis protocol, it is established that 2D nano-sized graphite carbon nitride can be produced in large quantities, with reproducible characteristics. The preliminary characterization of graphite carbon nitride was performed using XRD, SEM, TEM, Raman, FTIR, AFM, and BET techniques. The sizes of the nanosheets was found to be in the range of 200-300 nm, while the thickness of these sheets was ~90 nm. The performance of 2D nano-sized graphite carbon nitride in supercapacitors was investigated in detail. The electrochemical properties were investigated by cyclic voltammetry and charge-discharge measurements in 3 M KOH. The results clearly indicated improved cyclic stabilities up to 2500 cycles, with a specific capacitance of 84 F g-1 at 1 A g-1 current density. A typical charge-discharge profile (as a function of current density) for the synthesized g-C3N4 is shown in Fig. 1. A symmetric supercapacitor was also fabricated using this material as an active electrode, which showed ~ 11Wh Kg-1 energy and 500 W Kg-1 power density. The versatilaty of the material is established by extending its application to biosensing and catalytic applications. The results of electrochemical sensor for the detection of hydrogen peroxide is also presented in the paper. The result of cyclic voltammetry and chronoamperometric experiments showed that the linear response ranges are 0-80 nM, with a detection limit of 0.42 nM. The materials also shows excellent capability to catalytically reduce p-nitrophenol, which is a common pollutant in industrial waste water. Figure 1