demonstrated the synthesis of NiO-ZnO-modified g-C3N4 hierarchical composites via a simple hydrothermal method, in which the g-C3N4 nanosheets served as the matrix for the attachment of NiO and ZnO nanoparticles . The NiO-ZnO@g-C3N4 showed the SBET of 168.1 m 2 g - capacitance of 346.2 F g -1 at 0.5 A g -1 , and the 65% cycling stability after 1000 cycles. The NiO-ZnO@g-C3N4 electrode displayed the energy density of 7.91 W h Kg -1 at a power density of 160 W Kg -1 , which was found to be higher than that of NiO-ZnO (2.93 W h Kg -1 ) and pure g-C3N4 (1.60 W h Kg -1 ). The higher specific surface area, and improved electronic conductivity of the NiO-ZnO@g-C3N4 composite has significantly promoted the electron transfer and ion diffusion for enhanced electrochemical performance. were performed in 0.5 M H2SO4. The constant current charge-discharge profiles were recorded at 1 A g -1 , and the specific capacitances of 99, 101, 300, and 175 F g -1 were revealed for GCN/Bio-C0, GCN/Bio-C10, GCN/Bio-C20, and GCN/Bio-C30, respectively as shown in one-pot synthesis of Co3O4@g-C3N4 hybrid for dual applications i.e., supercapacitors and degradation of pollutants in water . In this study, the g-C3N4 was synthesized via thermal condensation of melamine, and pure Co3O4 was obtained by thermal decomposition of cobalt nitrate. The Co3O4@g-C3N4 hybrid was synthesized by mixing melamine with cobalt nitride, and heated at 550 ˚C for 2 h. The Co3O4 and Co3O4@g-C3N4 displayed the SBET of 6.0 and 13.1 m 2 g -1 , respectively. The Co3O4@g-C3N4 electrode revealed a higher specific capacitance of ~ 457.2 F g -1 at 1 A g -1 than that of pristine Co3O4 (~ 193.3 F g -1 ) and pristine g-C3N4 (106.6 F g -1 ) in 3 M KOH aqueous electrolyte. Further, a symmetric supercapacitor was fabricated using two identical Co3O4@g-C3N4 electrodes, and obtained a specific capacitance of ~ 92 F g -1 at 1 A g -1 , cycling stability of ~ 92% over 5000 cycles, and Coulombic efficiency of 94% after 5000 cycles. The Co3O4@g-C3N4 symmetric supercapacitor delivered the maximum energy density and power density of 11.3 W h Kg -1 and 1800 W Kg -1 , respectively. The higher supercapacitive performance of the studied electrode materials were attributed to the surface area, and higher porosity for the non-faradaic and faradaic process. Ce doped SnO2/g-C3N4 composites by hydrothermal method, and studied its bifunctional performance for asymmetric supercapacitor and visible light photocatalytic applications . The EDX analysis of Ce-SnO2@ g-C3N4 showed N, and O heteroatoms with 1.3, and 51.9 at. %, respectively. Under three-electrode setup with 2 M KOH electrolyte solution, the Ce-SnO2@ g-C3N4 composite electrode delivered the highest specific capacitance of 274 F g -1 at 1 A g -1 , while compared to that of g-C3N4 (32 F g -1 ), SnO2 (124 F g -1 ), Ce-SnO2 (130 F g -1 ), and SnO2@g-C3N4 (245 F g -1 ). The Ce-SnO2@g-C3N4 electrode showed the capacitance retention of 81.85% after 5000 charge/discharge cycles. Further, the asymmetric supercapacitor (ASC) full cell device was fabricated using Ce-SnO2@ g-C3N4, and activated carbon (AC) as positive and negative electrodes, respectively. The Ce-SnO2@g-C3N4//AC showed the energy density of 39.3 W h Kg -1 and the power density of 7425 W Kg -1 , and displayed the retention of 84.2% after completing 5000 cycles. Ramesh et al. reported the fabrication of Cu2O nanoflakes, CdFe2O4 nanoparticles placed on g-C3N4 sheets (Cu-CdFe/g) using a hydrothermal and wet impregnation process using melamine as the precursor for g-C3N4 sheets . The electrochemical studies were carried out in a three-electrode system using 2 M KOH aqueous solution and the GCD curves recorded for g-C3N4, Cu2O, CdFe, Cu/g, CdFe/g, Cu-CdFe/g electrodes at 0.25 A g -1 are shown in Fig. . The Cu-CdFe/g showed the specific capacitance of 1067 F g -1 at 0.25 A g -1 , which was about 1.4 times higher than that of Cu2O (250 F g -1 ), g-C3N4 (204 F g -1 ), and the binary composite Cu-CdFe (742 F g -1 ) electrodes.