Preparation of two-dimensional porous nitrogen‑oxygen co-doped recycled yeast cell wall derived‑carbon matrix for high-performance zinc ion supercapacitors

Zinc ion hybrid supercapacitors (ZIHCs) have great potential to become next-generation energy storage devices due to their high-power density, low-priced raw materials, high safety, and excellent stable cycle life. Herein, the two-dimensional (2D) porous Nitrogen‑oxygen co-doped yeast cell wall derived‑carbon with a large specific surface area is synthesized via a molten salt method by mixing urea with yeast cell walls in an air atmosphere for ZIHC cathodes. The results demonstrate that the microstructure of porous biomass carbon can be regulated by the content of urea. Together with the large specific surface area, controlled morphology and hetero-element doping (nitrogen and oxygen), the biomass carbon cathodes exhibit satisfactory electrochemical performance in supercapacitors and ZIHCs. In the three-electrode system for supercapacitors, the optimal biomass carbon blended with 20 wt% urea (NAC-20) provides a surprising 103 % capacity retention after 10,000 ultra-long lifetimes and presents an energy density of 37 W h kg−1 at 91 W kg−1 for ZIHCs. By connecting two ZIHCs in series, a light-emitting diode can light up for 5 min. This work provides a green and effective strategy through molten salt method and heterogeneous element doping, which lights the way to improve the electrochemical properties of similar high-performance electrochemical storage devices.