Carbon Nanosphere-Encapsulated Fe Core-Shell Structures for Catalytic CO₂Hydrogenation

We synthesized a unique carbon nanosphere (CNS)-encapsulated Fe core-shell catalyst (CNS-Fe) for CO2 hydrogenation. The synthesized CNS-Fe catalyst exhibited a core-shell structure with a core of ca. 40 nm containing iron species and a shell thickness of ca. 10 nm composed of mainly graphitic carbon. X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis were used to characterize the fresh and spent CNS-Fe catalysts and reveal a mixture of Fe3O4, metallic Fe, and Fe5C2 in the core and graphitic carbon as the shell with defect sites. Hydrogen temperature-programmed reduction, X-ray absorption near-edge structure, and extended X-ray absorption fine structure for the fresh CNS-Fe confirmed the composition of the iron species encapsulated in the CNS. The catalytic performance of CNS-Fe was investigated at ambient pressure for CO2 hydrogenation with hydrocarbons (CH4, C2-C4=, C2-C40), and CO was observed as the main product.