(449b) Boosting Ru/MgO Catalyst for CO Production in CO2 Hydrogenation

Recent reports suggest that the CO₂ methanation pathway on Ru catalysts for CO₂ hydrogenation could be altered towards the reverse water-gas shift (RWGS) reaction pathway for CO production [1, 2], a versatile raw material for producing value-added products through processes such as the Fischer-Tropsch synthesis. However, their current low efficiency in CO production necessitates further improvement for potential industrial applications, and the underlying structure-activity relationship in CO₂ hydrogenation remains unclear.

In this work, Ru/MgO catalysts with Ru in the form of single atoms (Ru₁) and a combination of single atoms and small Ru clusters (Ru₁-Ru_C) were prepared for CO₂ hydrogenation. It was demonstrated that the Ru₁-Ru_C/MgO catalyst, featuring Ru single atoms and small Ru clusters with a size of 0.6-1.0 nm, showed the CO yield (38.5%) that was 2.8 times of that (13.8%) on Ru₁/MgO at 600 ^oC. As confirmed by H₂-TPR, the presence of Ru_C facilitated the H₂ dissociation. On Ru₁ sites, CO₂ hydrogenation followed the RWGS pathway, resulting in the production of CO. In contrast, on Ru_C sites, the enhanced H₂ dissociation ability, along with the presence of adsorbed bidentate and monodentate carbonate species at the Ru-MgO interface, facilitated the formation of CH₄ through the CO₂ methanation pathway. Consequently, a composite structure comprising both Ru₁ and Ru_C size on MgO should be favored for the CO₂ hydrogenation reaction to efficiently generate the value-added CO. In addition, our research revealed that by engineering the Ru-CeO₂ interfaces, the CO yield could reach 50.4% on Ru-CeO₂/MgO, which was 3.6 times of that on Ru₁/MgO. These findings demonstrate the significant impact of Ru structure and local coordination environment within Ru/MgO catalysts on the CO₂ hydrogenation reaction pathway.

References:

[1] H. Xin, et al., J. Am. Chem. Soc. 2022, 144, 4874.

[2] A. Aitbekova, et al., J. Am. Chem. Soc. 2018, 140, 13736.