Enhancing low-temperature CO2 methanation over Ni-based catalysts with Mn modifying: Catalytic activity and mechanistic elucidation

Nickel-based catalysts are widely employed in CO2 methanation, but their effectiveness at low temperatures remains challenging. Herein, a series of Mn-promoted Ni/gamma-Al2O3 catalyst (xMn-NA) for CO2 methanation at low-temperature was developed, and the promoting mechanisms were clarified. The optimal 1Mn-NA catalyst exhibited 88.9 % CO2 conversion and nearly 100 % CH4 selectivity at a temperature as low as 220 degrees C. A series of characterization experiments suggested that incorporation of Mn into Ni-based catalyst modified the surface properties, promoting CO2 adsorption at medium basic sites, improving the catalyst's reducibility, and enhancing H2 adsorption/spillover, thereby improving the low-temperature activity. Furthermore, in situ DRIFTS experiments and theoretical calculations revealed that the formate route was the dominant reaction pathway, with Mn facilitating the formation of key intermediate HCOO* species, consequently enhancing the CO2 methanation activity. With its excellent low-temperature performance, the 1Mn-NA catalyst showcases great potential for scale-up applications in CO2 utilization.