Iron Nitride Nanoparticles Research Articles

Encapsulation of Iron Nitride by Fe–N–C Shell Enabling Highly Efficient Electroreduction of CO2 to CO

The conversion of CO2 into valuable chemicals has captured extensive attention for its significance in energy storage and greenhouse gas alleviation, but the development of cost-effective electrocatalysts with high activity and selectivity remains the bottleneck. Herein, we designed a Fe–N–C nanofiber catalyst featuring a core–shell structure consisting of iron nitride nanoparticles encapsulated within Fe and N codoped carbon layers that can efficiently catalyze CO2 to CO with nearly 100% selectivity, high faradic efficiency (∼95%), and remarkable durability at −0.53 V versus reversible hydrogen electrode. Theoretical calculations reveal that the introduction of an iron nitride core can facilitate the CO intermediate desorption from the Fe and N codoped shell, thus enhancing the catalytic performance of CO2 reduction. This work presents an ideal approach to rationally design and develop transition-metal and N codoped carbon materials for efficient CO2 reduction.

Catalysis for Low-Temperature Fuel Cells

Today, the development of active and stable catalysts still represents a challenge to be overcome in the research field of low-temperature fuel cells.[...]

Highly dispersed iron nitride nanoparticles embedded in N doped carbon as a high performance electrocatalyst for oxygen reduction reaction

The iron nitride nanoparticles embedded in N doped carbon catalyst material has been successfully synthesized and employed as a promising alternative for oxygen reduction reaction (ORR). The resultant catalyst exhibits superior electrocatalytic activity, good stability and low cost. Here, we pay more attention to “high dispersion” of iron, nitrogen and carbon. We developed a uniform dispersed FeNC catalyst synthesized by one-pot method, which exhibits superior electrocatalytic activity for ORR in alkaline media. Moreover, we also studied the influence of various pyrolysis temperatures and different mass ratio of nitrogen precursors and iron source on ORR electrocatalytic activity.

Oxygen Reduction Electrocatalysts Based on Coupled Iron Nitride Nanoparticles with Nitrogen-Doped Carbon

Aimed at developing a highly active and stable non-precious metal electrocatalyst for oxygen reduction reaction (ORR), a novel FexNy/NC nanocomposite—that is composed of highly dispersed iron nitride nanoparticles supported on nitrogen-doped carbon (NC)—was prepared by pyrolyzing carbon black with an iron-containing precursor in an NH3 atmosphere. The influence of the various synthetic parameters such as the Fe precursor, Fe content, pyrolysis temperature and pyrolysis time on ORR performance of the prepared iron nitride nanoparticles was investigated. The formed phases were determined by experimental and simulated X-ray diffraction (XRD) of numerous iron nitride species. We found that Fe3N phase creates superactive non-metallic catalytic sites for ORR that are more active than those of the constituents. The optimized Fe3N/NC nanocomposite exhibited excellent ORR activity and a direct four-electron pathway in alkaline solution. Furthermore, the hybrid material showed outstanding catalytic durability in alkaline electrolyte, even after 4,000 potential cycles.

Insights into the nitridation of zero-valent iron nanoparticles for the facile synthesis of iron nitride nanoparticles

The process of nitridation of zero-valent iron nanoparticles (ZVINPs) is investigated by employing two different synthesis strategies such as solvothermal method and gas diffusion using N2 and NH3.

ChemInform Abstract: Large Scale Synthesis and Formation Mechanism of Highly Magnetic and Stable Iron Nitride (ε‐Fe3N) Nanoparticles.

Abstractε‐Fe3N magnetic nanospheres of an average 45 nm size are prepared by nitriding Fe nanoparticles with gaseous NH3 (alumina boat, 650 °C, 4 h).

Large scale synthesis and formation mechanism of highly magnetic and stable iron nitride (ε-Fe3N) nanoparticles

We have demonstrated the large-scale synthesis of highly magnetic and stable iron nitride nanoparticles through nitridation of zero-valent iron nanoparticles.

Influence of pyrolysis temperature on oxygen reduction reaction activity of carbon-incorporating iron nitride/nitrogen-doped graphene nanosheets catalyst

Carbon-incorporating iron nitride nanoparticles deposited onto nitrogen-doped graphene nanosheets (FeCN/NG) as an alternative non-noble metal catalyst was successfully synthesized by pyrolysis under an ammonia atmosphere in this study. Influence of pyrolysis temperature on its crystalline structure, oxidative valence, morphology, chemical environment and catalytic activity of each FeCN/NG catalyst was examined by X-ray diffractometer, X-ray absorption near edge spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and rotating ring-disk electrode technique, respectively. The optimally sized FeCN nanoparticles around 10 nm were obtained at a pyrolysis temperature of 700 °C, delivering favorable oxygen reduction reaction (ORR) activity in the acid medium. After the durability test of 2000 cycles, not only the onset potential was not significantly shifted but also more than 80% retention on its ORR activity recorded at 0.5 V was achieved, demonstrating its catalytic stability.

Iron Nitride and Carbide: from Crystalline Nanoparticles to Stable Aqueous Dispersions

Iron nitride and carbide nanoparticles were synthesized using iron oxide particles as template. They were furthermore dispersed in aqueous solution via stabilization with a poly(ionic liquid). They provide a great potential combining a high saturation magnetization with low toxicity compared to the iron based compounds that are currently used in several applications such as cell-sorting and hyperthermia or as contrast enhancers for magnetic resonance imaging. We here present a sustainable and green procedure to synthesize iron nitride and carbide by resorting to the variety of iron oxide template nanoparticles. In this way the shape and the size can be precisely controlled and tuned within the nanometer range. During calcination, urea enables to control the composition of the product material, whereas a biopolymer agar protects the particles from agglomeration. We dispersed the particles in water by using poly(1-ethyl-3-vinylimidazolium bromide) as stabilizing agent. Magnetic measurements of the converted particles show that particles with a diameter of 18 nm are located at the border of superparamagnetic and ferromagnetic behavior. As expected after conversion the saturation magnetization of the particles was notably increased. The herein presented synthetic approach can be applied to other metals and has thus the potential to be important for the synthesis of nitrides and carbides in general.

Nitrogen-doped graphene nanosheet-supported non-precious iron nitride nanoparticles as an efficient electrocatalyst for oxygen reduction

Nitrogen-doped graphene-supported carbon-containing iron nitride (FeCN/NG) was synthesized by the chemical impregnation of iron and nitrogen-containing precursors in the presence of ammonia under thermal treatment. The resultant graphene-based material acted as an electrode with a much higher electrocatalytic activity in the catalysis via a 4-electron pathway in fuel cells. The results of X-ray diffraction, scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy indicated that graphite oxide was successfully reduced to nitrogen-doped graphene. X-Ray absorption spectroscopy further confirmed that carbon was incorporated into iron nitride, demonstrating that Fe–N–C catalytic active sites may be responsible for the oxygen reduction reaction. To the best of our knowledge, this is the first report of the combination of N-doped graphene with non-precious metal for oxygen reduction in fuel cells, and may open up a new possibility for preparing graphene-based nanoassemblies for intensive applications.

Low-Temperature Nitridation of Fe Nanoparticles Precursor

Nitridation of Fe nanoparticle precursor was performed in a NH3 atmosphere at the temperatures of 473 K and 673 K for one hour. Fe nanoparticles precursor had a typical spherical shape with iron oxides shell and alpha-Fe core, which was obtained by an arc-discharge method. Up to date, the nitriding temperature of 473 K in present work was the lowest by thermal ammonolysis method because of the characteristics of the nano-sized particles. The resultant product after nitridation was a mixture of iron-nitrides (gamma'-Fe4N and epsilon-Fe3N) nanoparticles with homogeneous dispersion. The nitriding mechanism, oxidizing behaviors and magnetic properties of iron-nitride nanoparticles were measured and discussed.

Preparation and Characterization of Fe–N Nanoparticles by Gas Flow Sputtering

Iron nitride (Fe–N) nanoparticles were prepared by reactive gas flow sputtering. The structure, size distribution, and magnetic properties of these particles were studied as a function of the average atomic ratio of N against Fe (N/Fe ratio). X-ray diffraction analysis revealed that the mixture of α-Fe and γ'-Fe4N was formed at an N/Fe ratio of approximately 0.2 and ε-Fe2–3N began to appear at an N/Fe ratio of approximately 0.4. Using transmission electron microscopy, it was found that α-Fe and γ'-Fe4N crystallites were not formed in one particle; instead, Fe particles and γ'-Fe4N particles coexisted. The size distribution was well fitted by a log–normal distribution; the mean diameter and standard deviation were approximately 50 and 15 nm, respectively, and were independent of the N/Fe ratio. The saturation magnetization decreased monotonously with an increase in the N/Fe ratio.

Magnetic investigation of iron-nitride-based magnetic fluid

Transmission electron microscopy (TEM), Mossbauer spectroscopy and magnetization measurements were used in the present study to investigate a non-aqueous iron-nitride-based magnetic fluid (MF) sample containing about 2 × 1016 particle/cm3. The TEM micrographs indicated spherical-shaped iron nitride nanoparticles with an average diameter of 12.3 nm and diameter dispersity of 0.14. The 77 K Mossbauer spectrum of the frozen MF sample indicated the presence of about 95% of the γ′-Fe4N phase, with a residual 5% of the ɛ-Fe4N phase. The temperature dependence of the magnetization was investigated under zero-field-cooled (ZFC) condition, in the temperature range of 4 to 165 K. The ZFC-data were curve-fitted using a new approach that takes into account the particle size distribution and the temperature dependence of the magnetocrystalline anisotropy, making the description of the experimental situation more realistic.