▎ 摘　　要

Over the years supercapacitors have established themselves as energy storage devices as well as a subject to reckon with. Thus, not surprisingly tremendous effort has been put in the field of supercapacitor research. However, a device with all desirable characteristics has not yet been realized and hence deserves to be paid utmost heed. Herein, we report a facile synthesis of porous graphene-NiO (PGNO) nanocomposites via a unique mixed solvent system through a solvothermal approach. The microscopic characterization of porous graphene (PG) reveals the presence of pores in the graphene sheets, NiO (NO) shows flake like structure and PGNO composite displays the anchoring of NO nanoflakes on the PG sheets. A series of electrode materials were prepared by varying the percentage composition of PG and the materials were named as 5-30 PGNO, respectively. The electrochemical study represented a good capacitance value of 511.0 F g(-1) at a scan rate of 5 mV s(-1) for the 10 PGNO composite in a 3-electrode method and 80% retention of initial capacitance after 10,000 cycles at a current density of 8 A g(-1). The fabricated symmetrical hybrid supercapacitor by using the 10 PGNO electrodes also depicted a good capacitance value of 86.0 F g(-1) at a scan rate of 5 mV s(-1). The fabricated device retained 84% of initial capacitance at the end of 10,000 cycles at a current density of 8 A g(-1), demonstrating the good electrochemical strength and rate capability of the material. The percentage of double layer capacitance and pseudocapacitance contributions to the overall specific capacitance of the PGNO supercapacitor has also been estimated. Overall, the results exhibited by the composite material warrants its beneficial utility in energy storage devices. (C) 2020 Elsevier B.V. All rights reserved.