Carbon dioxide-assisted fabrication of highly uniform submicron-sized colloidal carbon spheres via hydrothermal carbonization using soft drink

Abstract

An eco-friendly and economical method for the formation of highly uniform-sized carbon spheres by hydrothermal dehydration/condensation of a commercial carbonated beverage at 200 °C is reported. Until now, the effect of an extra pressure which is built up by dissolved CO2 on the generation of carbon spheres under hydrothermal condition less than 250 °C hasn’t been demonstrated yet. In general, a complicated reactor is required to put overpressure on the autoclave vessel by adding inert gases, whereas the manipulation of a carbonated beverage including fructose and glucose molecules as precursors is favorable to design a simple experimental set-up and to investigate the effect of extra pressure on the growth of carbon spheres under mild hydrothermal condition. Herein, CO2 dissolved in the beverage accelerates the dehydration kinetics of the dissolved sugar molecules leading to production of homogeneous carbon spheres having a diameter less than 850 nm. In addition, the rough surface of these carbon spheres likely results from continuous Ostwald ripening of constituent microscopic carbon-containing spheres that are formed by subsequent polymerization of intermediate hydroxymethylfurfural molecules.