Surface Iron Species in Palladium-Iron Intermetallic Nanocrystals that Promote and Stabilize CO2 Methanation

Abstract

It is of pivotal importance to develop efficient catalysts and investigate the intrinsic mechanism for CO₂ methanation. Now, it is reported that PdFe intermetallic nanocrystals afforded high activity and stability for CO₂ methanation. The mass activity of fct-PdFe nanocrystals reached 5.3 mmol g^-1 h^-1 , under 1 bar (CO₂ :H₂ =1:4) at 180 °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 CO₂ methanation. The metallic Fe in PdFe intermetallic nanocrystals induced the direct conversion of CO₂ into CO* as the intermediate, contributing to the enhanced activity.

Keywords: CO2 hydrogenation; intermetallic nanocrystals; iron; palladium.