Lattice Mn Doping Enables Dual-Pathway CO2 Methanation on Ru/Cr2O3

Rational design of highly active catalysts for low-temperature CO 2 methanation remains a critical challenge for efficient CO 2 utilization. Herein, we demonstrate that Mn incorporation into the Cr 2 O 3 lattice, rather than surface modification, markedly enhances the catalytic performance of Ru/Cr 2 O 3 catalysts. The optimal Ru/Mn 0.10 Cr 0.90 O x catalyst (2.24 wt % Ru) achieves 91% CO 2 conversion at 200 ° C with a space velocity of 36,000 mL g cat –1 h –1 , substantially exceeding that of the parent Ru/Cr 2 O 3 (4% at 200 ° C). Compared with Ru/Cr 2 O 3 , Ru/Mn 0.10 Cr 0.90 O x exhibits a 4.1-fold higher turnover frequency at 180 ° C, confirming the intrinsic catalytic enhancement conferred by Mn lattice doping. Comprehensive characterization revealed that Mn lattice doping generates Mn-O-Cr bonds, creating distinct Ru/O-Cr-O v -Mn interfacial sites in contrast to the Ru/O-Cr-O v -Cr interfaces present in undoped Ru/Cr 2 O 3 . In situ DRIFTS and H 2 -TPSR-MS studies demonstrated that low-temperature CO 2 methanation on Ru/Mn 0.10 Cr 0.90 O x proceeds concurrently via both CO* and HCOO* intermediate pathways, whereas only the CO* pathway operates on Ru/Cr 2 O 3 . DFT calculations revealed that Mn doping selectively modulates CO 2 adsorption at the interface while minimally affecting bridged Ru sites. At the Ru/O-Cr-O v -Mn interface, oxygen vacancies form and regenerate more readily than at the Ru/O-Cr-O v -Cr interface during CO 2 methanation, enabling an additional HCOO* pathway. This dual-pathway mechanism fundamentally underpins the enhanced low-temperature activity of Ru/Mn 0.10 Cr 0.90 O x and provides a promising design strategy for developing efficient CO 2 methanation catalysts.