Superhydrophobic banana stem–derived carbon aerogel for oil and organic adsorptions and energy storage

The porous 3D structure of zinc-doped carbon aerogel is created from cellulose precursor extracted from banana stem—a biomass waste that is abundant in Vietnam—through a simple and easy-to-implement 2-step process. Additionally, sodium alginate was used as a crosslinker and zinc acetate as a network coupling agent that can strengthen the gel system and increase the porosity of the carbon aerogel. In addition, zinc acetate also acts as a doping agent, increasing the ionic mobility of the material. Zinc-doped carbon aerogels synthesized from banana stem (Zn-BS-CA) have outstanding characteristics such as high specific surface area (up to 115 m²/g), diverse pore shapes, high porosity of the material, and low bulk specific gravity. Characterization of Zn-BS-CA was shown through modern methods (scanning electron microscope, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray crystallography, energy-dispersive X-ray, and nitrogen adsorption–desorption isotherms). Zn-BS-CA reached a maximum oil adsorption capacity of 34,997 g/g and a specific capacitance of 74 F/g for Zn-BS-CA pyrolyzed at 700 °C (Zn-BS-CA700). More importantly, Zn-BS-CA 700 shows capacity retention of 95% after over 500 cycles. The above results indicate high oil adsorption and energy storage capabilities of Zn-BS-CA.