Green fabrication of pore-modulated carbon aerogels using a biological template for high-energy density supercapacitors

Abstract

Pore modulation of carbon structures with low cost is of great importance for promoting the large-scale application of advanced supercapacitors. Herein, we innovatively propose a method for the directional preparation of hierarchical porous carbon materials using carbon aerogels assisted by mantis shrimp shells. The chitosan-based aerogel realizes self-assembly crosslinking in the mantis shrimp shell template possessing ordered pore arrays, with the template removed to obtain carbon materials with the corresponding pore structure after pre-carbonization, which is conducive to the full mixing of subsequent activators. The elimination of CaCO₃ in the template and the further activation of carbon materials promote the formation of a porous structure. Thanks to the reasonable pore size distribution, high specific surface area and N/O doping of the carbon materials, a high specific capacitance of 401 F g⁻¹ (0.5 A g⁻¹) is achieved as an electrode material in a three-electrode system with 6 M KOH electrolyte. The pore distribution of the carbon materials at 0.5 and 0.8 nm enables the symmetric supercapacitors with the EMIMBF₄ ionic liquid electrolyte to achieve an ultra-high energy density of 82.5 W h kg⁻¹ (437.5 W kg⁻¹). Further, the capacitance characteristics and ion diffusion rate are revealed in depth by Trasatti and Dunn's method as well as ion diffusion kinetic analysis. In addition, the transient distribution of electrolytes with different pore structures is simulated by COMSOL Multiphysics, which confirms that the hierarchical porous structure prepared with the assistance of mantis shrimp shells is more beneficial to the rapid diffusion of ions.