Single-Hole Hollow Carbon Nanospheres via a Poly(ethylene glycol)-Assisted Emulsion-Templating Strategy for Intensified Liquid-Phase Adsorption

Single-hole hollow carbon nanospheres (HCH) possess uniqueproperties that combine the advantages of a hollow cavity and an opening hole inthe shell, making them very attractive in various applications. However, it is still achallenge to synthesize HCH via a facile and scalable route. Herein, we develop apoly(ethylene glycol) (PEG)-assisted emulsion-templating method to synthesizeHCH, involving only a hydrothermal process and pyrolysis. In the emulsionsystem, the PEG molecules can be used as a reverse demulsifier to induce theformation of hollow structures with a closed shell (HCS, PEG-1000), a singlehole in the shell (HCH, PEG-2000), and a bowl-like shell (HCB, PEG-4000). Itis found that HCH exhibits higher adsorption capacities (2-4 times higher thanthose of HCS) and faster adsorption rates toward large molecules (e.g., Congored), indicating the intensification of liquid-phase adsorption induced by thesingle-hole hollow structure, which can promote mass transfer and simulta-neously enhance the adsorption capacity.