Tuned selectivity and enhanced activity of CO₂ methanation over Ru catalysts by modified metal-carbonate interfaces

Carbonate-modified metal-support interfaces allow Ru/MnCO₃ catalyst to exhibit over 99% selectivity, great specific activity and long-term anti-CO poisoning stability in atmospheric CO₂ methanation. As a contrast, Ru/MnO catalyst with metal-oxide interfaces prefers reverse water–gas shift rather than methanation route, along with a remarkably lower activity and a less than 15% CH₄ selectivity. The carbonate-modified interfaces are found to stabilize the Ru species and activate CO₂ and H₂ molecules. Ru-CO* species are identified as the reaction intermediates steadily formed from CO₂ dissociation, which show moderate adsorption strength and high reactivity in further hydrogenation to CH₄. Furthermore, carbonates of Ru/MnCO₃ are found to be consumed by hydrogenation to form CH₄ and replenished by exchange with CO₂, which are in a dynamic equilibrium during the reaction. Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique catalytic functions for selective CO₂ hydrogenation.