A systematic study on Equisetum ramosissimum Desf. derived honeycomb porous carbon for supercapacitors: Insight into the preparation-structure-performance relationship

It is always of considerable significance for the development of high-performance carbon-based supercapacitors to regulate the porosity and understand the preparation-structure-performance relationship. In this work, a KOH-assisted hydrothermal pre-treatment combined with pyrolysis strategy is successfully employed to fabricate N -doped honeycomb-like three-dimensional porous carbon from Equisetum ramosissimum Desf. weeds. The pore structure is well-regulated by tuning the KOH concentration and carbonization temperature, thus optimizing the electrochemical properties. Three types of pore structures are proposed, and their differences and connections in terms of preparation and electrochemical performance are systematically explored. The carbon sample with the optimized pore structure delivers a high specific capacitance of 427 F g-1 at 0.2 A g-1 in the aqueous KOH electrolyte. When assembled into an aqueous symmetric supercapacitor device, the energy density reaches up to 30.9 Wh kg- 1 at a power density of 500 W kg-1. The results indicate that a moderate Vmirco/Vmeso should play the key role in the excellent rate capability, while the co-contribution of double-layer capacitance and pseudo -capacitance as well as the rational pore size regulation should be responsible for the high specific capacitance.