Unveiling the Activity Origin of Iron Nitride as Catalytic Material for Efficient Hydrogenation of CO₂ to C₂₊ Hydrocarbons

Abstract

Developing efficient catalytic materials and unveiling the active species are significant for selective hydrogenation of CO2 to C2+ hydrocarbons. Fe2N@C nanoparticles were reported to exhibit outstanding performance toward selective CO2 hydrogenation to C2+ hydrocarbons (C2+ selectivity: 53.96 %; C2‐C4= selectivity, 31.03 %), outperforming corresponding Fe@C. In situ X‐ray diffraction, ex situ Mössbauer and X‐ray photoelectron spectra revealed that iron nitrides were in situ converted to highly active iron carbides, which acted as the real active species. Moreover, the combined results of in situ diffuse reflectance infrared Fourier transform spectroscopy and control experiments suggested an in situ formed carbonyl iron‐mediated conversion mechanism from iron nitrides to iron carbides.

High C2-C4 selectivity in CO2 hydrogenation by particle size control of Co-Fe alloy nanoparticles wrapped on N-doped graphitic carbon

“…The activity of sample 3 is markedly higher than that of most active Fe or Co-based catalysts and even ruthenium, nickel, or molybdenum-based catalysts found in the literature. Table S12 summarizes the selectivity for C 2 -C 4 hydrocarbons reported in previous studies on CO 2 hydrogenation ( Baddour et al., 2020 ; Cored et al., 2019 ; Jiang et al., 2018 ; Kim et al., 2020 ; Liu et al., 2018 ; Mutschler et al., 2018 ; Wang et al., 2018 ; Yan et al., 2019 ; Zhao et al., 2021 ).…”

“…Information from molecular electrostatic potential (MEP) surface analysis of non-supported (M1) and supported (G1) Co-Fe cluster model reveals two extremely positive [+34 eV (M1)] and negative [-22 eV (M1)] regions which become much attenuated [+14 and −18 eV (G1)] when the Co-Fe NP is interacting with graphene ( Figure 7 A). Overall, it is easy to foresee that positive regions (blue color) should be repulsive for CO 2 [δ + (C) = 0.30] adsorption, whereas strong adsorption should be expected for negative regions (red color), even though highly negative regions do not assist the subsequent desorption process ( Zhao et al., 2021 ). Therefore, it is suggested that the catalysis takes place in the boundary between the afore-mentioned negative and positive regions.…”

Comprehensive Understandings into Complete Reconstruction of Precatalysts: Synthesis, Applications, and Characterizations

“…provided the depth understanding of reconstruction mechanism of nitride catalyst during CO 2 hydrogenation via various characterizations. [ 229 ] The in situ formed carbonyl iron was detected and recognized as the key intermediate for the conversion from nitride to carbide. To sum up, it is urgent to further explore the scientific issues including the reconstruction chemistry of precatalysts, the recognition of the fine structure for reconstructed species, the relationship between catalyst structure and catalytic activity, as well as the identification of real active sites.…”

“…studied core–shell carbon wrapped iron nitride (Fe 2 N@C) nanoparticles for efficient hydrogenation of CO 2 to C 2+ hydrocarbons. [ 229 ] The time‐dependent crystal phase reconstruction was confirmed via in situ XRD measurements. During CO 2 hydrogenation, the diffraction peaks for Fe 2 N were vanished and there was a complete phase change from Fe 2 N to Fe 2.5 C, and the formed one was recognized as the veritable active species.…”

“…implemented in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to uncover the phase reconstruction mechanism during CO 2 hydrogenation of Fe 2 N precatalyst. [ 229 ] The in situ formed carbonyl iron intermediate was detected, which was responsible for the conversion mechanism from iron nitrides to iron carbides. This intermediate was not detectable by in situ XRD, which suggests the superiority of in situ FTIR in the detection of reconstructed intermediates.…”