Rapid transformation of heterocyclic building blocks into nanoporous carbons for high-performance supercapacitors

The ever-increasing global energy consumption necessitates the development of efficient energy conversion and storage devices. Nitrogen-doped porous carbons as electrode materials for supercapacitors feature superior electrochemical performances compared to pristine activated carbons. Herein, a facile synthetic strategy including solid-state mixing of benzimidazole as an inexpensive single-source precursor of nitrogen and carbon and zinc chloride as a high temperature solvent/activator followed by pyrolysis of the mixture (T = 700-1000 °C under Ar) is introduced. The addition of ZnCl₂ prevents early sublimation of benzimidazole and promotes carbonization and pore generation. The sample obtained under the optimal carbonization temperature of 900 °C and ZnCl₂/benzimidazole weight ratio of 2/1 (ZBIDC-2-900) features a moderate specific surface area of 855 m² g^-1, high N-doping level (10 wt%), and a wide micropore size distribution (∼1 nm). ZBIDC-2-900 as a supercapacitor electrode exhibits a large gravimetric capacitance of 332 F g^-1 (at 1 A g^-1 in 1 M H₂SO₄) thanks to the cooperative advantages of the electrochemical activity of the nitrogen functional groups and the accessible porosity. The excellent capacitance performance coupled with robust cyclic stability, high yield and straightforward synthesis of the proposed carbons holds great potential for large-scale energy storage applications.