Ultra-Thin Conductive Graphitic Carbon Nitride Assembly through van der Waals Epitaxy toward High-Energy-Density Flexible Supercapacitors.

Abstract

Graphitic carbon nitride is an ordered two-dimensional stability. However, its bulk structure with low electrical conductivity (less than 1 S cm^-1) restricts the applications in electrochemical energy storage. This is because conventional synthesis methods lack effective thickness control, and the excessive nitrogen doping (∼50%) leads to poor electrical conductivity. Here, we report an ultrathin conductive graphitic carbon nitride assembly (thickness of ∼1.0 nm) through graphene-templated van der Waals epitaxial strategy with high electrical conductivity (12.2 S cm^-1), narrow pore-size distribution (5.3 nm), large surface area (724.9 m² g^-1), and appropriate nitrogen doping level (18.29%). The ultra-thin structure with nitrogen doping provided numerous channels and active sites for effective ion transportation and storage, while the graphene layers acted as micro current collectors; subsequently, it exhibits high energy storage capability of 936 mF cm^-2 at 1 mA cm^-2 with excellent stability of over 10 000 cycles. Moreover, the all-solid-state supercapacitors showed an ultra-high energy density of 281.3 μWh cm^-2 at 1 mA cm^-2 with high rate capability, Coulombic efficiency, and flexibility. This work represents a general framework for the bottom-up synthesis of ultrathin 2D materials, which may promote the application of graphitic carbon nitride in energy storage.