Ultrafine Fe₂C Iron Carbide Nanoclusters Trapped in Topological Carbon Defects for Efficient Electroreduction of Carbon Dioxide

Abstract

Normally, the CO2 reduction reaction (CO2RR) on Fe‐based materials is unfavorable due to the poisoning of reaction sites by CO products. By modulating the electronic structures of Fe sites via carbonization, the CO binding strength can be optimized to facilitate the CO2RR. In the present study, a dual N‐elimination strategy is adopted to synthesize and stabilize a rarely reported iron carbide phase Fe2C nanoclusters with a mean diameter of 1.07 nm trapped in topological carbon defects. Notably, the ultrafine Fe2C clusters present an excellent performance on electrocatalytic CO2RR, which can drive a current density of 8.53 mA cm−2 with Faradaic efficiency of 97.1% for CO production at −0.7 V versus reversible hydrogen electrode. Density functional theory calculations reveal that the nanometric Fe2C cluster possesses much weaker binding with CO than the Fe crystalline surfaces and other iron carbides, thus promoting the CO desorption and overall CO2RR process.

Enhancing Electrocatalytic CO2-to-CO Conversion by Weakening CO Binding through Nitrogen Integration in the Metallic Fe Catalyst

“…After the stability test, the SEM and XRD results (Figure S9) indicate that the morphology and structure of the N–Fe@NC catalyst remain nearly unchanged. Remarkably, such exceptional performance of N–Fe@NC can be compared to the best CO 2 RR outcomes among the reported Fe-based electrocatalysts, as listed in Table S5. ,,,,,− …”

“…16−18 Even worse, Fe has been shown to act as a relatively robust catalyst for the hydrogen evolution reaction (HER), which is the primary competing reaction accompanying with the CO 2 RR process, further reducing the already low selectivity for CO generation. 19,20 Hence, it remains of significant importance to develop highly active Fe-based catalysts for the CO 2 RR with high selectivity toward the CO product.…”

“…16,22,27−29 raised by the high-energy valence orbitals of p-block elements upon their incorporation into Fe, consequently lowering its dband center relative to Fermi level. 19 Among such p-block elements, nitrogen (N) is the most commonly employed nonmetal dopant heteroatom. 3 The rational design and construction of Fe−N compounds are expected to improve the CO 2 RR performance of Fe-based materials.…”

“…In particular, the electrochemical CO 2 reduction reaction (CO 2 RR) is considered as a promising approach to addressing energy and environmental challenges through leveraging renewable energy sources to convert CO 2 into value-added chemicals and fuels. − Among the various CO 2 RR products, carbon monoxide (CO) holds significant importance as the primary chemical feedstock and intermediate in the widespread manufacturing of bulk chemicals, medicine, and gas fuels. , In recent years, there has been extensive research on transitional metal-based materials to improve the CO 2 RR performance for CO generation, in terms of higher product generation rate, selectivity, and long-term durability. − Iron (Fe) is one of the cheapest and most earth-abundant transitional metals, with partially filled d subshells make Fe-based materials promising candidates for catalytic applications. − However, there is limited attention given to the study of Fe-based catalysts for CO 2 RR electrocatalysis in the recent literature. This may be because Fe particles and compounds normally display sluggish kinetics for CO 2 RR, mainly attributed to the strong binding of Fe active centers and CO molecules. − Even worse, Fe has been shown to act as a relatively robust catalyst for the hydrogen evolution reaction (HER), which is the primary competing reaction accompanying with the CO 2 RR process, further reducing the already low selectivity for CO generation. , Hence, it remains of significant importance to develop highly active Fe-based catalysts for the CO 2 RR with high selectivity toward the CO product.…”

Modulation of the electronic structure of metallic bismuth catalysts by cerium doping to facilitate electrocatalytic CO2 reduction to formate

“…3a, suggesting its superior CO 2 RR activity compared with other Bi-based catalysts. The step-potential electrolysis was conducted at the applied potentials ranging from −0.8 to −1.3 V vs. RHE with on-line monitoring of the as-generated gas products, 50,51 while the liquid-phase products were quantified by 1H nuclear magnetic resonance (NMR) analysis using DMSO as an internal standard after electrolysis (Fig. S13†).…”