Ultrahigh nitrogen-doped carbon derived from g-C3N4 assisted by citric acid for superior potassium-ion storage

Nitrogen-doped carbon is regarded as a promising anode for potassium ion batteries (PIBs) because nitrogen atoms can regulate the structures of carbon and generate abundant active sites. How to improve the nitrogen content in carbon through simple and effective methods remains to be further addressed. In this paper, a carbon material (60NC) with ultrahigh nitrogen content (16 %) was prepared from graphite phase carbon nitride (g-C3N4) by a convenient freeze-drying and high-temperature pyrolysis method, assisted by citric acid. When used as an anode for PIBs, 60NC exhibited a superior reversible capacity of 318.1 mAh g−1 after 200 cycles at 0.1 A g−1. Even at the high current density of 1A g−1, 60NC maintained a specific capacity of 261.8 mAh g−1 after 1000 cycles. The excellent electrochemical performance of 60NC mainly stems from its abundant K+ storage active sites caused by nitrogen doping, large layer spacing, and hierarchical porous structure. [Display omitted] •Preparation of 2D ultra-high nitrogen-doped carbon by citric acid assisted g-C3N4.•Excellent potassium storage performance of 60NC anode studied.•The 60NC possesses ultra-stable long-cycle performance (83.9 % capacity retention with 1000 cycles) at 1 A g−1.