Hierarchical Porous Carbon Foams Synthesized by Highly Efficient Microwave Pyrolysis for Supercapacitors

Abstract

Carbon, as an ideal electrode material for supercapacitors, plays an indelible role in the development of energy storage. Sufficient specific surface area, suitable pore distribution, and disordered graphite-like domains are the three factors that coregulate the double-layer capacitance of carbon. However, the preparation of porous carbon is still limited to uneconomical fossil raw materials, complex energy-consuming carbonization processes, and unsatisfactory properties. With the improvement of people's requirements for supercapacitors, efficient, fast, and energy-saving carbon preparation has become a key research direction of supercapacitors. In this paper, a simple and fast microwave pyrolysis method was designed to prepare porous carbon materials by using potassium citrate as a carbon source and sodium chloride as a protective molten salt. The designed electrodes have a disordered carbon layer spacing structure and a uniform distribution of micropores, which benefit from thermal diffusion from inside to outside by microwave heating and the high-frequency vibration pyrolysis mode at the molecular level. The reaction time of a few minutes can make the specific surface area of activated carbon reach 1316 m² g^-1. The mass-specific capacitance of the sample in the three-electrode system is 302 F g^-1 (0.1 A g^-1), and the assembled device can be used after 10,000 charge and discharge cycles and maintains a high capacitance retention rate (76.39%). The preparation method conforms to the concept of "green chemistry", promotes the revelation of the mechanism of the microwave chemical reaction system, and has visible practical production potential.