Cohen in 1989, predicted β-C3N4, a new covalent compound based on the crystal structure of β-Si3N4, and prepared β-C3N4 in 1993, which was amazingly found to be much harder than diamond. Through theoretical calculations, reported the five different phases of C3N4, specifically α-C3N4, β-C3N4, cubic-C3N4, pseudocubic-C3N4, and g-C3N4 with the bandgap values of . Among these five phases, the narrowest bandgap and good light absorption is shown by g-C3N4 . Tri-s-triazine (C6N7) and triazine (C3N3) rings are the basic two structural units of g-C3N4, of which tri-striazine structure is more stable. Both C6N7 and C3N3 rings are connected by C-N bonds to form a layered structure with uniform distribution of triangular nanopores, which is different from graphene layers formed by the closely connected honeycomb structure. g-C3N4 is a n-type semiconductor, and possess two dimensional and three-dimensional graphitic carbon due to the presence of very high N2 content occupied by a pyridinic and graphitic nitrogen. g-C3N4 is the most stable allotrope under ambient conditions in C3N4 with a thermal stability upto 600 ˚C in air, and cannot be dissolved in acidic, alkali, or organic solvents . The chemical inertness and poor solubility of g-C3N4, are the two main reasons for it has been not utilized well for some period of time. In 2009, Wang and co-workers reported that g-C3N4 has a moderate band gap of 2.7 eV with a conduction and valence band positions at -1.3 eV and +1.4 eV, respectively, and can act as a visible-light active metal-free polymeric semiconductor photocatalyst suitable for hydrogen evolution reaction (HER) . Ever since, the research focus on g-C3N4 materials were increased for various applications like photocatalytic water splitting, carbon dioxide (CO2) photoreduction, and electrocatalytic hydrogen evolution. g-C3N4 has the layer spacing of about 0.326 nm, which is slightly lesser than that of graphite and shows electrical conductivity less than 1 S cm -1 . The intrinsically high N content (57.1 at%), abundant pores and defects in g-C3N4, makes them suitable for supercapacitors and batteries . The utilization of g-C3N4 in the arena of supercapacitors started in the beginning of 21 st century, and has become unprecedentedly hot in recent years. However, the synthesis of g-C3N4 via the traditional high-temperature solid-state reaction results in a bulk phase material, with a poor specific surface area. Two-dimensional (2D) g-C3N4 shows various intriguing physicochemical properties, compared with the bulk phase g-C3N4. 2D g-C3N4 are mono-or few-layered g-C3N4, which have the structure similar to graphene, and composed of tri-s-triazine units bridged by amino groups, with dangle hydrogens in the C-N layers and periodic vacancies in lattices. The specific surface area of 2D g-C3N4 nanosheets is significantly enhanced due to the ultrathin nanostructure with defective and disorder framework in the range from 50 to 400 m 2 g -1 , which is much higher than the bulk phase g-C3N4 with a specific surface area of 10 m 2 g -1 . There is resistance to the transfer of electrons in between the layers of g-C3N4, makes the 2D g-C3N4 as more conducting material. In the tri-s-triazine layers of g-C3N4, triangular nanopores are uniformly distributed and results in strong in-plane piezoelectricity. Specifically, stronger piezoelectricity is attained in the case of 2D g-C3N4 due to the presence of thin layered nanosheets with a large number of polar tri-s-triazine groups in the layers. 2D g-C3N4 shows enlarged bandgap compared to the bulk phase g-C3N4 due to the quantum size effect. The few layered morphology and uniformly distributed triangular nanopores in 2D g-C3N4, exposes large number of edge sites and provides the convenience for the modification using some specific strategies, such as elemental doping, and interface engineering, etc . 2D g-C3N4 is promising material for applications in electrochemical techniques, due to the presence of higher content of nitrogen.