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

Abstract

Abstract 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 CO 2 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 (α‐Fe 2 O 3 and γ‐Fe 2 O 3 ) during activation and CO 2 hydrogenation were elaborated, that is, α‐Fe 2 O 3 (γ‐Fe 2 O 3 )→α‐Fe 3 O 4 (γ‐Fe 3 O 4 )→α‐Fe (γ‐Fe)→χ‐Fe 5 C 2 (θ‐Fe 3 C). Both iron carbides showed high catalytic activities while χ‐Fe 5 C 2 exhibited higher selectivity to lower olefins but weaker chain growth probability than θ‐Fe 3 C.