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.

Dynamic structural evolution of iron catalysts involving competitive oxidation and carburization during CO 2 hydrogenation

“…Similarly, Zhang et al (26) tracked the transformation of the mixture of Fe and Fe 3 O 4 by using in situ XRD and Raman and observed the carburization of -Fe to -Fe 5 C 2 and -Fe to -Fe 3 C. Besides carburization, they also showed that the CO-activated Fe 5 C 2 is oxidized to Fe 3 O 4 in CO 2 hydrogenation (27). Such a transformation strongly depends on the precursors of the catalysts, their microstructure, reaction, and treatment conditions (20,24,28). After the pre-reduction, Fe(0) is commonly used for CO 2 hydrogenation and the performance changes with TOS (29,30).…”

Addressing the CO2 challenge through thermocatalytic hydrogenation to carbon monoxide, methanol and methane

“…In contrast, PdFe nanocrystals were reported as active and selective for CO 2 methanation. 278 This work revealed that the face-centered tetragonal phase is more resilient during reactive conditions with respect to face-centered-cubic PdFe nanocrystals. Similarly, the modification of the shape of palladium nanoparticles implies the exposition of different facets for a Pd/SiO 2 material.…”

Vacancy-cluster-mediated surface activation for boosting CO2 chemical fixation

“…As shown in Figure 3b, Arrhenius plots were obtained based on the linear fitting of ln TOF vs. 1000/T. 38 Remarkably, the activation energy for FeOCl-V Fe-Cl nanosheets is 55.5 ± 1.6 kJ mol -1 , which is significantly less than that for FeOCl-V Cl nanosheets (130.2 ± 7.8 kJ mol -1 ), further indicating the positive role of vacancy cluster in boosting ring opening of epoxides. The recyclability and stability of FeOCl-V Fe-Cl nanosheets was examined by 5 consecutive reaction cycles, in which the catalytic performance of FeOCl-V Fe-Cl nanosheets was well maintained (Figure 3c).…”