Unveiling the role of cobalt in the product regulation for CO2 hydrogenation to light olefins over alumina-supported Co-Fe catalysts

Abstract

CoFe-based catalysts for CO2 hydrogenation reactions have been widely studied, but the effects of cobalt on the product regulation remains largely over-looked. In the present study, we report a series of Na-decorated alumina-supported Co-Fe bimetallic catalysts with varying Co/Fe molar ratios for the direct conversion of CO2 to light olefins. In situ XRD and Mössbauer spectroscopy reveal that Co doping significantly promotes the reduction and carburization of Fe species, leading to the formation of active CoFe alloy carbides. Furthermore, the DFT results indicate that cobalt decreases the H2 adsorption energy, thereby regulating the surface C/H ratio and enhancing the tandem RWGS and Fischer-Tropsch reactions. These effects synergistically improve the formation and desorption of light olefins. As a result, the optimal Co1Fe2 catalyst (Co/Fe = 1/2) achieves a high STY of 315.1 g kgcat−1 h−1 for light olefins with a CO2 conversion of 51.9% at 320 °C. This study provides mechanistic insights into cobalt-assisted product selectivity control and offers a promising strategy for designing highly efficient CO2-to-light olefins catalytic systems.