Electronic and Compositional Modulation of SMSI States for Selective CO₂ Hydrogenation with Rhodium Catalysts

The role of TiO2, ZnO, and ZnTiO3 as supports for rhodium has been investigated for the CO2 hydrogenation. Rh/TiO2 demonstrated a high selectivity for CH4, which is typical for Rh catalysts; however, Rh/ZnO and Rh/ZnTiO3 shifted the product selectivity to CO almost exclusively. The difference in behavior is attributed to the modulation of strong metal–support interactions (SMSIs) by the supports. Detailed characterization revealed the formation of a distinct metallic Zn overlayer covering the RhZnx alloyed nanoparticle in Rh/ZnO, altering the electronic states of Rh, and a RhTix overlayer in Rh/ZnTiO3, suppressing the CO adsorption on Rh in bridged and tilted geometry and polarizing the CO bond. These structural features significantly modify the CO adsorption strength and mode, together with the intermediate hydrogenation behavior, influencing product formation. The study highlights the potential of tailoring SMSI states by modifying the support composition and interfacial coupling with metal nanoparticles, enabling improved CO-selective hydrogenation. These findings offer deeper insights into engineering metal–support interactions, with broad implications for advancing industrial processes involving CO, including Fischer–Tropsch synthesis, the water–gas shift reaction, and methanol synthesis.