Unveiling the roles of Fe-Co interactions over ternary spinel-type ZnCoxFe2-xO4 catalysts for highly efficient CO2 hydrogenation to produce light olefins

Abstract

Abstract Currently, the CO2 conversion to light olefins is attractive in clean energy research. Despite numerous works on Co-Fe bimetallic catalysts, the lack of well-defined bulk structures with identical crystalline phase and similar textural property hinders the in-depth understanding of the roles of Fe and Co species. Herein, series of uniform K-containing spinel-type ZnCoxFe2-xO4 nanoparticles (x\u202f=\u202f0, 0.5, 1.0, 1.5, 2.0) were successfully synthesized via a single source layered double hydroxide precursor route. Compared to ZnFe2O4 and ZnCo2O4, as-fabricated ternary ZnCo0.5Fe1.5O4 spinel nanoparticles as the catalyst exhibited an outstanding performance toward CO2 hydrogenation to produce light olefins, with a 36.1% selectivity toward C2=-C4= products at a 49.6% conversion and an unprecedentedly high iron time yield for CO2 conversion to light olefins (∼29.1 μmolCO2·gFe−1·s−1) at the gaseous hourly space velocity of 24000\u202fmL·gcat−1·h−1. In combination with structural characterizations and reaction results, it was unveiled that during the CO2 hydrogenation over ternary ZnCoxFe2-xO4 catalysts, the formation of electron-rich Fe0 atoms in the CoFe alloy phase significantly promoted in situ the generation of active iron-cobalt carbide, Co2C, and θ-Fe3C phases, thereby improving the reactivity of catalysts for the production of hydrocarbons and simultaneously inhibiting both the CO2 methanation and the secondary hydrogenation of olefins. The present findings provide a clear understanding of the roles of Fe-Co interactions over ternary ZnCoxFe2-xO4 catalysts for the highly efficient hydrogenation of CO2 to produce light olefins.