Filter Paper-Derived Hierarchical Porous Carbon by a Simple Molten Salt Strategy in Air for High-Performance Supercapacitors

Carbon materials are widely used as electrode materials for supercapacitors due to their low cost and high porosity. The traditional preparation scheme requires the participation of inert gas, and the electrochemical performance exhibited still leaves much to be desired. Here, a hierarchical porous structure with a large specific surface area is successfully constructed through a simple molten salt strategy with low-cost filter paper as the precursor and urea as the nitrogen source. Molten salt can function as both a sealant, maintaining the integrity of the prepared carbon structure, and a template, facilitating the formation of pores within the carbon material. Incorporating nitrogen atoms into carbon materials creates additional electrochemical active sites, facilitating enhanced redox reactions and improving the electrochemical performance. The prepared FPAC/Urea-3:4 (FPAC: filter paper-based activated carbon) has an impressive large specific surface area of 1020 m2 g–1 and abundant heteroatom doping. In the three-electrode system, the specific capacitance of FPAC/Urea-3:4 can reach 230.8 F g–1 at 1 A g–1. The study also investigated the potential application of FPAC/Urea-3:4 in symmetric supercapacitors, with an energy density of 7.4 Wh kg–1 and a specific power of 125.3 W kg–1, and the device can light up an LED lamp. In addition, it also showed excellent cycle stability with a capacitance retention rate of up to 97.7% after 5000 cycles. This study proposes an efficient and promising application technology for the preparation of porous carbon in air.