Graphene-coupled nitrogen-enriched porous carbon nanosheets for energy storage

Abstract

Two-dimensional (2D) soft materials have attracted much attention recently due to their unique carbon-rich structure and extensive potential applications for energy storage. Although the specific surface areas (SSAs) of 2D soft materials are theoretically high, practically maintaining both the uniform 2D morphology and high SSA of a single 2D soft material is still challenging. Herein, graphene-coupled covalent triazine-based frameworks (G-CTFs) with typical 2D features, large aspect ratio, and ultrahigh SSA of up to 1584 m² g⁻¹ were synthesized through polymerization of p-benzenedinitrile in molten salt in the presence of p-benzonitrile-functionalized reduced graphene oxide. After their direct pyrolysis, nitrogen-enriched porous carbon nanosheets (G-PCs) can be easily obtained, which had the frameworks' 2D morphology and exhibited a high nitrogen content and even higher SSA of up to 1982/3021 m² g⁻¹, as calculated using the Brunauer–Emmett–Teller and Langmuir methods, respectively. Benefiting from these features, the G-PCs exhibited excellent energy storage performance as electrode materials in both a Li-ion battery (235 mA h g⁻¹ at 5 A g⁻¹ for 3000 cycles), Na-ion battery (138 mA h g⁻¹ at 1 A g⁻¹ for 500 cycles), and supercapacitor (340 F g⁻¹ at 0.1 A g⁻¹ and 10 000 stable charge–discharge cycles at 5 A g⁻¹). All these results indicate that the 2D sandwich-like porous carbon materials could be promising candidates for high-performance energy storage devices.