Operando Spectroscopic Study of Dynamic Structure of Iron Oxide Catalysts during CO2 Hydrogenation

Understanding of dynamic structure of active sites is of paramount importance for rational design of industrial catalysts. This work revealed the structure evolution of iron active phases for CO2 hydrogenation over iron-based catalysts. With a combination of operando Raman spectroscopy and X-ray Diffraction coupled with online gas chromatography, the panoramic structure evolution of iron oxides (alpha-Fe2O3 and gamma-Fe2O3) during activation and CO2 hydrogenation were elaborated, that is, alpha-Fe2O3 (gamma-Fe2O3)->alpha-Fe3O4 (gamma-Fe3O4)->alpha-Fe (gamma-Fe)->chi-Fe5C2 (theta-Fe3C). Both iron carbides showed high catalytic activities while chi-Fe5C2 exhibited higher selectivity to lower olefins but weaker chain growth probability than theta-Fe3C.