Nitrogen-doped porous carbon/graphene nanosheets derived from two-dimensional conjugated microporous polymer sandwiches with promising capacitive performance

Abstract

Conjugated microporous polymers (CMPs) are considered as promising precursors to fabricate multi-functional porous carbons. However, CMPs are formed under kinetic control, and most of them are obtained as amorphous powders without long-range order. Carbon materials derived from CMPs usually preserve the particular structure of the CMP precursors, thus the direct pyrolysis of CMPs into two-dimensional (2D) porous carbon nanosheets remains a great challenge. In this work, 4-iodophenyl-substituted graphene (RGO-I) is used both as a building block and a structure directing template for the construction of nitrogen–rich graphene–CMP (GMP) sandwiches using a solution-based approach. The 2D structure of RGO-I with its large aspect ratio allows for the growth of uniform CMP shells onto both sides of the graphene sheets. Thereby, aggregation and restacking of the graphene sheets can be effectively suppressed even during high-temperature treatment. Thereby, well-defined nitrogen-doped porous carbon/graphene nanosheets were readily obtained by direct pyrolysis of the GMP sandwiches. The sandwich-like nitrogen-doped porous carbon/graphene nanosheets were used as electrode materials for supercapacitor devices with very promising capacitive performance, superior in comparison to the corresponding porous carbons derived from the graphene-free CMPs. The good 2D electron transport ability of graphene together with the intimate interactions between porous carbon and graphene layers provide a combination of large electrochemically active surface area for charge transfer and minimized ion diffusion paths during the charge/discharge process. This unique set of physical properties effectively boosts the capacitive performance values if applied in supercapacitor devices.