Crucial Role of Surface FeO x Components on Supported Fe-Based Nanocatalysts for CO2 Hydrogenation to Light Olefins

Currently, Fe-based catalysts show excellent catalytic performance in the hydrogenation of CO2 to produce light olefins. Despite numerous studies, the identification of the role of catalytically active components over Fe-based catalysts for CO2 hydrogenation is not quite clear. In this work, a series of ZrO2-supported cobalt-doped Fe-based catalysts were fabricated by a microliquid film reactor-assisted coprecipitation method. It was demonstrated that appropriately strong interactions between Fe-containing species and the ZrO2 support in catalyst precursors could facilitate the generation of a defective FeO x component upon reduction treatment and inhibit the carburization of metallic iron during the reaction. Among all Fe-based catalysts, the catalyst bearing a (Co + Fe)/ZrO2 mass ratio of 3:7 and a Co/Fe molar ratio of 1:9 achieved a highest light olefins selectivity of about 38% at 49% CO2 conversion under reaction conditions (i.e., 320 °C, 2.0 MPa, and 4800 mL·gcat –1·h–1), along with a high Fe time yield to light olefins of 9.2 μmolCO2 ·gFe –1·s–1 and a low CO selectivity of 4.7%. Comprehensive structural characterization and catalytic CO2 hydrogenation experiments clarified that the surface-dominant defect-rich FeO x component as catalytically active species substantially played a crucial role in governing the hydrogenation of CO2, mainly owing to their enhanced adsorption and binding ability for CO2 and the CO intermediate. This study offers a new strategy to design Fe-based catalysts and provides deep insight into the role of iron oxide species for CO2 hydrogenation to produce light olefins.