Seaweed-like Nitrogen-Doped Porous Carbon Superstructures via an Ultrasonic Atomization Ice Template as High-Performance Electrodes in Supercapacitors

An ultrasonic atomization ice template (UAIT) strategy was discovered to produce polymer nanosheets that could be pyrolyzed into seaweed-like nitrogen-doped porous carbon. The high-frequency ultrasound was found to effectively atomize bulk solution into micron/submicron droplets, which amplified the surface area of the feed liquid and thereby facilitated the growth kinetics of the ice template in liquid nitrogen. This crucial factor is responsible for the formation of a uniquely structured nanosheet morphology and its assembly into a three-dimensional (3D) superstructure, which was next replicated in the final porous carbon product. The fabrication efficiency of the ultrasonic atomization step (single nozzle) ranges from 0.09 to 1.35 g h–1. The thicknesses of the as-synthesized carbon nanosheets were effectively adjusted by the concentration of the polymer precursor solution. Benefiting from a hierarchically porous, interconnected nanosheet-based architecture, a high specific surface area, and nitrogen doping, the as-obtained 3D carbon superstructure served as a high-performance electrode in supercapacitors and exhibited a high capacity, a superior rate capability, and long-term stability. This work will open up an avenue for the facile and scalable preparation of seaweed-like porous carbon superstructures with diverse functions and applications beyond supercapacitors.