Integration of H ₂ -activating metal clusters with metal oxides for boosting the low-temperature reverse water–gas shift reaction

The reverse water-gas shift (RWGS) reaction provides an important pathway for converting CO₂ to CO, which can then be used to produce high-value chemicals through Fischer-Tropsch synthesis. Metal oxide materials, especially Fe₂O₃, offer considerable potential for use in the RWGS reaction at high temperatures, but their catalytic performance is hindered by the inadequate activation and dissociation capabilities of H₂ at low temperatures. Herein, we report the introduction of Fe₄ with high H₂ activation capability near Fe₂O₃, which shows a synergistic effect and achieves excellent activity and selectivity in the RWGS reaction at low temperatures. Fe₂O₃ nanoparticles and Fe₄ clusters supported on carbon (Fe₂O₃-Fe₄/C) were prepared via KCl-assisted pyrolysis of NH₂-MIL-88B(Fe) precursors. Fe₂O₃-Fe₄/C delivers a remarkable CO selectivity of 99.4% and a space-time yield of 15.2 μmol_CO g_cat^-1 s^-1 at 350 °C under atmospheric pressure. <i>In situ</i> diffuse reflection infrared Fourier-transform spectra and density functional theory calculations demonstrate that the introduction of Fe₄ clusters can activate H₂ and significantly lower the reaction energy barrier of CO₂ hydrogenation on Fe₂O₃ sites, thus boosting the RWGS performance at low temperatures.