Shape-Shifting via Salt Crystallization: Conversion of a Nanostructured Polymer into a Site-Selective Nitrogen-Doped Carbon Sheet with Enhanced Supercapacitive Performance

The production of selective nitrogen-doped graphitic nanoporous carbon plays a pivotal role in performance enhancement and widens the scope of practical applications of functional materials. The synthesis of selective nitrogen-doped graphitic nanoporous carbon is very difficult because high temperature encourages the escape of nitrogen species during pyrolysis and there is a lack of suitable precursors. Here, we demonstrate the conversion of a zero-dimensional (0D) poly(N-methylaniline) (PNMA) hollow nanostructure into a 2D selective nitrogen-doped (pyridinic and pyrrolic) graphitic nanoporous carbon sheet (NGPCS) at high temperature (1000 °C). Before carbonization, PNMA is sealed using sodium chloride salt that acted as a nanoreactor in the course of carbonization. It promotes the 2D sheet formation, graphitization, and high incorporation of nitrogen species (atom % of ∼8.6) within the carbon framework. NGPCS15 materials (the number indicates the weight ratio of PNMA and NaCl) display excellent electrochemical capacitive performance (277.9 F g–1 at a scan rate of 2 mV s–1), good rate capability, and outstanding cyclic stability (no loss of specific capacitance after 5000 cycles). We believe that NGPCS15 can be used as an advanced electrochemical supercapacitor.