Switch CO2 Hydrogenation Selectivity from CH4 to CO by Decorating Sulfur on Ru Nanoparticles

The hydrogenation of CO 2 to CO represents a promising synthetic pathway to replace coal gasification and methane reforming. Ru-based catalysts showed high activity in CO 2 hydrogenation but lower CO selectivity due to competing methanation reactions. Here, we reported a surface sulfur (S) decoration strategy to shift the methanation to 99% selectivity for CO on the Ru/TiO 2 catalyst in CO 2 hydrogenation. The optimized 2%Ru/TiO 2 -SO catalyst achieved a CO 2 conversion of 57.9% with 100% CO selectivity at 550 ° C, and it operated stably even in a reaction gas containing an H 2 S impurity. Notably, even after high-temperature oxidation treatment at 800 ° C, the 2%Ru/TiO 2 -SO catalyst still retains high CO selectivity (>98.2%). Structural characterization confirms strong S–Ru interactions between S species and Ru nanoparticles in S-decorated catalysts, with highly dispersed S species bonded to the Ru surface as S 2− , thereby leaving the surface Ru atoms in an electron-deficient state. Mechanistic studies reveal that CO was formed via direct dissociation of CO 2 on this 2%Ru/TiO 2 -SO catalyst. The adsorption strength of CO* species and H 2 activation capacity were significantly suppressed on S-decorated catalysts featuring electron-deficient Ru species, thus inhibiting the deep hydrogenation of CO and enabling exclusive CO generation. The surface S decoration strategy employed here will provide insights and guidance for the design of supported metal catalysts with tunable selectivity in other heterogeneous catalytic hydrogenation reactions, particularly those operating at high temperatures.