A universal strategy towards porous carbons with ultrahigh specific surface area for high-performance symmetric supercapacitor applications

Porous carbons with ultrahigh specific surface area (> 3000 m²/g) prepared at low KOH/char ratio (e.g. less than 0.5) is of great importance for their future applications, yet this remains a significant challenge due to the uneven dispersion of the activating agent within carbon source. Herein, a universal combination strategy (solid-state reaction at room temperature followed by chemical activation) to prepare ultrahigh surface area porous carbons has been developed. The specific surface area can reach to 3775 m²/g even at a very low KOH/char ratio (0.19), and the morphologies, specific surface and pore size distributions of the products can be simply tuned by the KOH/char ratios. We found the solid-state reaction at room temperature prior to chemical activation is an efficient way to achieve the even dispersion of the activating agent and thus improve the utilization of KOH greatly. As a typical example, the as-obtained EDTA-3 K not only have an ultrahigh specific surface area up to 3614 m²/g, but also deliver a large total pore volume of 2.09 m³/g. Benefited from the ultrahigh specific surface area, hierarchically porous structure and unique morphology, the EDTA-3 K based supercapacitor exhibits excellent capacitive performance in both KOH and Li₂SO₄ electrolyte. Hence, this study not only exploits a new approach for the synthesis of hierarchically porous carbon materials with ultrahigh specific surface area for electrochemical energy storage applications, but also provides a universal combination strategy to improve the utilization ratio of activating reagent for the producing of porous carbons.