Surface Iron Species in a Palladium-Iron Intermetallic Promote and Stabilize CO2 Methanation.

CO 2 methanation exhibits great potentials in environmental remediation and renewable energy storage. Therefore, it is of pivotal importance to develop efficient catalysts and investigate the intrinsic mechanism for CO 2 methanation. Herein, we reported that PdFe intermetallic nanocrystals afforded high activity and stability for CO 2 methanation. The mass activity of fct -PdFe nanocrystals reached 5.3 mmol g -1 h -1 , under 1 bar (CO 2 :H 2 = 1:4) at 180 o C, being 6.6, 1.6, 3.3, and 5.3 times as high as that of fcc -PdFe nanocrystals, Ru/C, Ni/C, and Pd/C, respectively. After 20 rounds of successive reaction, 98% of the original activity was retained for PdFe intermetallic nanocrystals. Further mechanistic studies revealed that PdFe intermetallic nanocrystals enabled the maintenance of metallic Fe species via a reversible oxidation-reduction process in CO 2 methanation. The metallic Fe in PdFe intermetallic nanocrystals induced the direct conversion of CO 2 into CO* as the intermediate, contributing to the enhanced activity.