Regulating the Electronic Configuration of Supported Iron Nanoparticles for Electrochemical Catalytic Nitrogen Fixation

Abstract

Electrocatalytic nitrogen reduction reaction (eNRR) is a sustainable alternative to the traditional Haber-Bosch process due to its eco-friendly nature and capability of utilizing renewable energy. However, its low Faradic efficiency (FE), caused by the excessive adsorption and reduction of protons, has been regarded as the main challenge, which leads to low ammonia yield as well. Herein, a carbon-supported iron electrocatalyst is reported, which is fabricated by low-temperature (300 °C) potassium vapor reduction of FeF 3 -intercalated graphite fluoride, for efficient electrochemical nitrogen reduction. The strategy enables the unique formation of exposed Fe nanoparticles uniformly anchored on graphene and in situ doped with fluorine heteroatoms. These specific features can alter the electronic configuration of the Fe nanoparticles, leading to strong surface polarization that boosts nitrogen absorption capability for eNRR, resulting in high FE (41.6%) and ammonia yield rate (53.3 μg h -1 mg -1 ) simultaneously. First-principle calculation attributes this enhanced eNRR capability to more empty orbitals carried by the Fe atoms through the electron transfer with F dopant and substrate. As a versatile strategy for synthesizing various ultrafine and highly dispersed metal nanoparticles on the carbon support, this work might shed light on rational designing essential electrocatalysts with effective electronic structure manipulation.

Ultrasmall Iron Nanoparticle-Decorated Carbon Black for High-Efficiency Nitrate-to-Ammonia Electrosynthesis and Zinc-Nitrate Batteries

“…XPS was further used to measure the Fe species. High-resolution XPS Fe 2p spectrum of Fe@C-900 was fitted into 707.5, 710.8, 712.8, 720.0, 724.2, and 726.1 eV (Figure S6), which were ascribed to Fe 0 , Fe 2+ (2p 3/2 ), Fe 3+ (2p 3/2 ), Fe 0 , Fe 2+ (2p 1/2 ), and Fe 3+ (2p 1/2 ), indicating the presence of multiple valence states of Fe on the surface of Fe@C-900. − Although there was the presence of multiple valence states of Fe, the main Fe species was Fe 0 because the Fe NPs could be clearly observed on the CB surface (Figure c–e). The Fe content of Fe@C-900 (4.29 wt %) was tested by inductively coupled plasma-optical emission spectroscopy (ICP-OES) (Table S1).…”

Controlled etching to immobilize highly dispersed Fe in MXene for electrochemical ammonia production

“…The high‐resolution transmission electron microscopes (HRTEM) image shows an interplanar distance of 0.203 nm, which is consistent with the distance of (110) planes of Fe (Supporting Information: Figure S3B). [ 31 ] As shown in Figure 1b, after further etching with HCl solution, the as‐synthesized HD‐Fe‐MXene exhibits a looser and smoother 2D layered accordion‐like structure than that of Fe‐NPs‐MXene due to the removal of Fe nanoparticles on the surfaces of MXene. As illustrated in Figure 1c, the TEM image further reveals the abundant cracks in a 2D‐layered structure.…”

“…Fe, as an inexpensive and earth‐abundant element, has been proven to be a promising NRR electrocatalyst for its abundant d ‐orbital electrons and the unoccupied d orbitals, which could enhance the adsorption and activation of nitrogen molecules. [ 26,27 ] Recently, various Fe‐based materials, including Fe/Fe 3 O 4 , [ 28 ] Fe‐doped W 18 O 49 nanowires, [ 29 ] Fe‐SnO 2 , [ 30 ] F‐doped Fe@graphene, [ 31 ] Fe‐TiO 2 , [ 32 ] Fe‐MoS 2 , [ 33 ] Fe 3 S 4 , [ 34 ] Fe‐doped Cu 2− x S, [ 35 ] CNT@C 3 N 4 ‐Fe&Cu, [ 36 ] MXene/TiFeO x , [ 37 ] Fe SA ‐NO‐C, [ 38 ] and Fe SA /N‐doped carbon [ 39 ] have been explored as efficient catalysts for NRR. Among the above catalysts, Fe‐based single‐atom catalysts exhibit superior electrocatalytic NRR activities due to their maximum active sites and highly unsaturated coordination nature.…”

Interlinking electronic band properties in catalysts with electrochemical nitrogen reduction performance: a direct influence

“…The term 'doping' symbolizes the incorporation of heteroatom into a host material with an effort to tune electronic state and spin state resulting in charge redistribution which can be beneficial for the increase in active site selective adsorption of reactants [89], surface polarization [90] and feasible interfacial charge transfer [91]. Doping of electron rich or deficient heteroatoms into catalyst system can also manipulate the Fermi level position [92] of an electrocatalyst.…”