Unique CuOx–FeOx interfaces in Cu-decorated Fe-based catalysts facilitating CO2 hydrogenation to higher hydrocarbons

Abstract

Currently, research on iron-based catalysts applied in CO2 hydrogenation to higher hydrocarbon products (C2+), especially light olefins, has gained significant attention. However, a comprehensive understanding of the synergy between active Fe-containing species and promoters on their catalytic performances is still lacking. In this study, ZrO2-supported Cu-decorated iron catalysts were constructed through the coprecipitation with the aid of a microliquid-film reactor and evaluated in CO2 hydrogenation. It was shown that the incorporation of a small amount of Cu promoted the reduction of Fe species and facilitated the formation of surface defective Fe3O4 (FeOx) component containing a large number of oxygen vacancies and thus highly dispersed surface CuOx/FeOx structures. Notably, the 2.0 wt% Cu-incorporated Fe-based catalyst exhibited superior performance, along with high selectivity to C2+ products (77.1 %) and yield of C2+ products (27.3 %) under reaction conditions (i.e., 4800 mL·gcat-1·h−1, 2.0 MPa, and 320 ℃), outperforming the current state-of-the-art Fe-based catalysts. Through a combination of comprehensive structural characterizations and density functional theory calculations with reaction results, it was unveiled that surface FeOx favored CO2 adsorption and H2 dissociation, and meanwhile, CuOx component with high Cu+ fractions adjacent to FeOx on Cu-decorated Fe-based catalysts also could remarkably promote H2 dissociation and the adsorption of CO2 and CO intermediate. Therefore, such-generated unique CuOx–FeOx interfaces in Fe-based catalysts could facilitate the generation of adsorbed adjacent CHx species through both the hydrogen-assisted indirect dissociation pathway of CO intermediate and the formate intermediate pathway, thus promoting CO2 hydrogenation to higher hydrocarbons. This work affords a promising strategy for the construction of Fe-based based catalysts to boost CO2 hydrogenation to higher hydrocarbon products and a deep understanding of the role of CuOx–FeOx interfaces in CO2 hydrogenation.