Onion‐Like Graphene Carbon Nanospheres as Stable Catalysts for Carbon Monoxide and Methane Chlorination

Abstract Thermal treatment induces a modification in the nanostructure of carbon nanospheres that generates ordered hemi‐fullerene‐type graphene shells arranged in a concentric onion‐type structure. The catalytic reactivity of these structures is studied in comparison with that of the parent carbon material. The change in the surface reactivity induced by the transformation of the nanostructure, characterized by TEM, XRD, X‐ray photoelectron spectroscopy (XPS), Raman, and porosity measurements, is investigated by multipulses of Cl 2 in inert gas or in the presence of CH 4 or CO. The strained CC bonds (sp 2 ‐type) in the hemi‐fullerene‐type graphene shells induce unusually strong, but reversible, chemisorption of Cl 2 in molecular form. The active species in CH 4 and CO chlorination is probably in the radical‐like form. Highly strained CC bonds in the parent carbon materials react irreversibly with Cl 2 , inhibiting further reaction with CO. In addition, the higher presence of sp 3 ‐type defect sites promotes the formation of HCl with deactivation of the reactive CC sites. The nano‐ordering of the hemi‐fullerene‐type graphene thus reduces the presence of defects and transforms strained CC bonds, resulting in irreversible chemisorption of Cl 2 to catalytic sites able to perform selective chlorination.