Effect of adsorbate geometry and hydrogen bonding on the enhanced adsorption of VOCs by an interfacial Fe3O4-rGO heterostructure

Volatile organic compounds (VOCs) produced from a wide range of industrial and household chemicals are toxic to human health. Hence, effective VOC removal strategies such as adsorption are essential. Developing a carbon based adsorbent for the selective adsorption of VOCs without affecting its inherent adsorption capacity is challenging. In this study, we prepared three Fe3O4-doped reduced graphene oxide (Fe-rGO) materials via a liquid-phase reduction technique under acidic, neutral, and basic coagulation conditions. The Fe-rGO adsorbents exhibited a hydrolysis-induced GO network with a wrinkled layer morphology. Acidic conditions yielded an rGO surface with a large number of O-functional groups (epoxy and carboxylic groups), which act as anchoring sites for the growth of Fe3O4 nanoparticles. The synergistic effect of Fe3O4 domains and O active sites led to the effective and selective adsorption of amphiphilic VOCs including C4-C7 alkanes, ketones, and aromatic compounds (10.8-63.2 mg g-1). Experimental analyses and density functional theory calculations revealed three crucial factors that determine the improved amphiphilic VOC adsorption of the Fe-rGO materials: geometry of the adsorbate, hydrogen bonding at the rGO surface, and Fe3O4 nanoparticles controlling the charge density. Our facile and effective rGO surface manipulation strategy involving the fabrication of a metal oxide-carbon heterostructure provides a selective adsorption platform for amphiphilic VOCs.