▎ 摘　　要

Developing low-cost and highly effective electrode materials is crucial for advanced supercapacitors. In this work, N-doped graphene with an interconnected porous structure is prepared with a solvothermal method combined with freeze-drying. The hierarchical porous structure with a large specific surface area (291.3 m(2) g(-1)) and high total pore volume (0.418 cm(3) g(-1)) offers many adsorption sites and fast transfer channels for electrolyte ions, enhancing the supercapacitive performance. Also, the intrinsic oxygen and the doped nitrogen (9.95 at%)-based functional groups increase the hydrophilicity of the as-prepared electrode material and provide the additional pseudo-capacitance, further improving the supercapacitive behavior. Under the present conditions, the optimal graphene (denoted as hp-NGR-1.0), which is fabricated by using 1.0 mL of tetraethoxysilane, possesses a specific capacitance of 328.5 F g(-1) at 1.0 A g(-1) in the three-electrode device, and the corresponding symmetric configuration displays an energy density of 31.2 Wh kg(-1) at 400 W kg(-1), which is superior to many previous results. Also, the optimal material depicts good cycling stability and rate capability. The prominent properties endow hp-NGR-1.0 promising potentials in the fields of high-performance electric energy storage devices. (C) 2021 Elsevier B.V. All rights reserved.