Fe N-doped Carbon Research Articles

FeNC Catalysts Decorated with NiFe2O4 to Enhance Bifunctional Activity for Zn–Air Batteries

Rechargeable Zn–air battery is a promising next-generation energy storage device attributed to its high energy density, excellent safety, and low cost. However, its commercialization is hampered by sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at air electrodes. Herein, we have designed, fabricated, and demonstrated a highly efficient ORR/OER electrocatalyst, NiFe2O4/FeNC, using low-cost materials via a facile synthesis route. NiFe2O4 is successfully loaded on Fe/N-doped carbon (FeNC) through bonding to Fe3C in FeNC. Due to the existence of high ORR active sites such as FeN4 and Fe and N-doped carbon moieties, the half-wave potential of the ORR reaches a high value of 0.83 V. While benefited from NiFe2O4 with high OER activity and the synergistic effect between NiFe2O4 and FeNC, the overpotential is 310 mV at 10 mA cm–2 in the OER. The voltage difference between charging–discharging operations in the Zn–air battery employing the NiFe2O4/FeNC electrocatalyst only increases by 0.16 V after cycling for 100 h (600 cycles) at 10 mA cm–2, which is much lower than 1.28 V using the best commercial Pt/C and RuO2 catalysts.

PtFe and Fe3C nanoparticles encapsulated in Fe–N-doped carbon bowl toward the oxygen reduction reaction

The high-temperature calcination strategy facilitates the formation of alloy atoms but inevitably results in the aggregation and deactivation of the metal particles for the oxygen reduction reaction (ORR) electrocatalysts. Herein, we report the successful encapsulation of Platinum–Iron (PtFe) nanoparticles (∼4.7 nm) in the N-doped hollow carbon hemisphere matrix (NCB) containing Fe–N and Fe3C without employing high-temperature pyrolysis, which effectively facilitates the well-dispersed Pt nanoparticles and the formation of PtFe nanoalloys. The hollow carbon hemisphere structure contributes to the expansion of the specific surface area and exposure of active sites of the catalyst, meanwhile, the modification of the surface of the carbon nano-bowl from a predominantly Fe to a functional electrocatalyst with a primarily PtFe alloy can boost the ORR catalytic activity and stability. It is found that the Pt3Fe/Fe3C-NCB catalyst exhibits the optimum ORR performance with a mass activity (0.97 A mg−1Pt), 5.10 times higher than the commercial Pt/C (0.19 A mg−1Pt). Pt3Fe/Fe3C-NCB also displays excellent durability in comparison to the commercial Pt/C after 20,000 potential cycles. Combined with the Physical characterization and the electrochemical test results, Fe3C-NCB plays a strong metal-support role for the encapsulated PtFe nanoparticles structure, thereby preventing nanoparticle migration and corrosion. Experimental characterization and theoretical calculations show that the appropriate PtFe alloy composition and the strain effect induced by Fe–N/Fe3C active sites are sufficient to accelerate the detachment of oxygenated species from the alloy surface, resulting in a catalyst with excellent ORR performance.

Poly (acrylamide-co-acrylonitrile) hydrogel-derived iron-doped carbon foam electrocatalyst for enhancing oxygen reduction reaction in microbial fuel cell

Developing advanced non-precious metal catalysts for oxygen reduction reaction (ORR) is critical for microbial fuel cells (MFCs). Fe–N–C catalysts are considered the best successor to platinum-based catalysts for ORR. Herein, we have synthesized environmental friendly, cost-effective Fe–N-doped carbon foam catalyst [Fe-embedded poly (acrylamide-co-acrylonitrile) hydrogel-based carbon foam(Fe@Am-co-An/CF)] by using Fe-embedded poly (Am-co-An) hydrogel for MFCs. Poly(Am-co-An) hydrogel is used as a carbon and nitrogen precursor. The synthesized catalysts are characterized by FTIR, SEM, TEM, XRD and XPS. Furthermore, four different catalysts based on different ratios of the metal such as Fe@Am-co-An/CF (1:22), Fe@Am-co-An/CF (2:22), Fe@Am-co-An/CF (3:22), and Am-co-An/CF have been prepared. Results indicate that the Fe@Am-co-An/CF (2:22) catalyst exhibits the highest power density (736.06 mWm−2 at the current density of 1132.04 mAm−2) compared to the other catalysts. The results of CV, LSV, EIS, and chronoamperometry indicate that Fe@Am-co-An/CF (2:22) is the most promising catalyst for ORR activity in MFCs.

Tafel Slope Analysis from Inherent Rate Constants for Oxygen Reduction Reaction Over N-doped Carbon and Fe–N-doped Carbon Electrocatalysts

Tafel Slope Analysis from Inherent Rate Constants for Oxygen Reduction Reaction Over N-doped Carbon and Fe–N-doped Carbon Electrocatalysts

Two-Dimensional Fe-N-C Nanosheets for Efficient Oxygen Reduction Reaction

Fe-N-doped carbon (Fe-N-C)-based electrocatalysts are considered to be promising alternatives to replace Pt-based catalysts for oxygen reduction reactions (ORR). Here, we reported a simple and effective approach to prepare Fe-N-C-based electrocatalysts with the shape of two-dimensional nanosheets (termed Fe/NCNSs) to enhance the ORR performance. Fe/NCNSs were prepared by the calcination of Fe/Zn dual-metal ZIFs nanosheets as precursors. Benefiting from its higher specific surface area, electrochemically active surface area, and proportion of pyridinic N and Fe-N, the optimized Fe/NCNS showed excellent ORR performance both in acidic (E1/2 = 0.725 V vs. RHE) and alkaline (E1/2 = 0.865 vs. RHE) media, being 23 mV more negative and 24 mV more positive than that of a commercial Pt/C. The optimized Fe/NCNS also exhibited long durability. In addition, the Zn-air battery with Fe/NCNS-1 and RuO2 as the air catalyst exhibited high power density (1590 mW cm−2 at a current density of 2250 mA cm−2) and superior charging/discharging durability.

Molten-salt-assisted synthesis of onion-like Co/CoO@FeNC materials with boosting reversible oxygen electrocatalysis for rechargeable Zn-air battery

A melt-salt-assisted method is utilized to construct an onion-like hybrid with Co/CoO nanoparticles embedded in graphitic Fe-N-doped carbon shells (Co/CoO@FeNC) as a bifunctional electrocatalyst. The iron-polypyrrole (Fe-PPy) is firstly prepared with a reverse emulsion. Direct pyrolysis of Fe-PPy yields turbostratic Fe-N-doped carbon (FeNC) with excellent oxygen reduction reaction (ORR) electrocatalysis, while the melt salt (CoCl2) mediated pyrolysis of Fe-PPy obtains onion-like Co/CoO@FeNC with a reversible overvoltage value of 0.695 V, largely superior to Pt/C and IrO2 (0.771 V) and other Co-based catalysts reported so far. The ORR activity is mainly due to the graphitic FeNC and further enhanced by CoNx bonds, whereas the oxygen evolution reaction (OER) activity is principally due to the Co/CoO composite. Concurrently, Co/CoO@FeNC as cathode catalyst enables Zn-air battery with a high open circuit voltage of 1.42 V, a peak power density of 132.8 mW cm−2, a specific capacity of 813 mAh gZn−1, and long-term stability.

Fe–N-doped carbon nanoparticles from coal tar soot and its novel application as a high performance air-cathode catalyst for microbial fuel cells

Coal tar soot (CTS), which is an industrial product of the incomplete combustion of coal tars or heavy oil, is a low-value additive for the production of cement, ink, oil paint, etc. However, it has considerable potential as the catalyst support for oxygen reduction reactions (ORRs) because of its abundant oxygen-containing functional groups and interconnected porous structure. Herein, we proposed a one-pot strategy for synthesizing the high ORR performance catalyst (FePc@CTS) by simultaneously incorporating Fe and N into the carbon matrix of CTS and modifying the textural properties of CTS by using solvothermal treatment with iron phthalocyanine (FePc) and CTS in n-hexane. Electron microscopy investigation shows that the solvothermal treatment produces FePc@CTS with a spherical shape and a rather narrow particle size distribution. X-ray photoelectron spectroscopy and elemental analysis indicate that the FePc@CTS has a high Fe and N content. Due to the interconnected macroporous structure and the abundant ORR active sites, the FePc@CTS sample had the most positive half-wave potential (0.057 V vs. Ag/Cl) and the highest limiting current density (5.63 mA cm−2) among the prepared samples. An air-cathode microbial fuel cell (MFC) with FePc@CTS delivered a peak power density of 2026 ± 160 mW m−2, which was much higher than that of a cell with Pt/C (1337 ± 179 mW m−2). This work provides a facile pathway to convert low-value soot into interesting nano-structured ORR catalyst for MFCs to recover energy from wastewater.

Fe and N co-doped carbon derived from melamine resin capsuled biomass as efficient oxygen reduction catalyst for air-cathode microbial fuel cells

Cathode oxygen reduction reaction (ORR) performance is crucial for power generation of microbial fuel cells (MFCs). The current study provides a novel strategy to prepare Fe/N-doped carbon (Fe/N/C) catalyst for MFCs cathode through high temperature pyrolyzing of biomass capsuling melamine resin polymer. The obtained Fe/N/C can effectively enhance activity, selectivity and stability toward 4 e– ORR in pH neutral solution. Single chamber MFC with Fe/N/C air cathode produces maximum power density of 1166 mW m−2, which is 140% higher than AC cathode. The improved performance of Fe/N/C can be attributed to the involvement of nitrogen and iron species. The excellent stability can be attributed to the preferential structure of the catalyst. The moderate porosity of the catalyst facilitates mass transfer of oxygen and protons and prevents water flooding of triple-phase boundary where ORR occurs. The biomass particles encapsulated in the catalyst act as skeletons, which prevents catalyst collapse and agglomeration.

Characterization of Flame Synthesized Metal and Nitrogen Doped Nanocarbons for Oxygen Reduction Reaction

Carbon based electrocatalysts have shown demonstrable potential to replace platinum-based Oxygen Reduction Reaction (ORR) catalysts in low temperature fuel cells [1, 2]. The presence of a graphitic nano-shell surrounding the primary carbon particle and the formation of disordered sites in graphene through doping by nitrogen atoms, have been associated with activity towards the reduction of oxygen [3]. In addition, the introduction of transition metal atoms results in the formation of M-Nx moieties and carbon encapsulated metal-rich nanoparticles, drastically increasing the ORR activity [4]. It has also been reported that the synthesis process significantly affects the catalytic activity and performance in fuel cell electrodes of the doped carbon catalysts [1]. Therefore, the influence of the synthesis process and the effect of dopant atoms on the morphological and physico-chemical characteristics of metal, nitrogen doped carbon deserves a more detailed analysis in order to understand the correlation between process parameters and catalytic activity. This study looks at the morphological, chemical, structural and electrochemical properties of doped nanocarbons with special emphasis on Fe, N doped carbon (Fe-N-C) electrocatalysts. A novel flame-based synthesis technique, capable of generating partially graphitized carbon black, with a primary particle size ranging from 10 to 15 nm is also discussed in relation to the catalyst synthesis process (figure 1 a-c). Metal and nitrogen doped nanocarbon ORR catalysts were synthesized by a modified flame spray pyrolysis-based deposition technique called Reactive Spray Deposition Technology (RSDT) [5]. The carbonaceous material was synthesized directly from atomized organic solvents and precursors by pyrolysis at flame temperatures exceeding 1500°C. A sheath of nitrogen gas surrounding the flame and controlled oxygen flow rates were utilized to control the flame equivalence ratio and ensure incomplete combustion of the organic material resulting in the formation of carbonaceous material. The levels nitrogen and metal doping were controlled by selecting the concentrations of nitrogen and metal precursors during RSDT deposition. The structure of the carbon was analyzed using a combination of X-Ray Diffraction (XRD), Raman spectroscopy and high resolution Transmission Electron Microscopy (TEM) as shown in figure 1 d-f. XRD and Raman results indicated the presence of partially graphitized carbon [6] with highly disordered structure resulting from the incorporation of the dopant atoms into the graphene layers, which was correlated to an increase in ORR activity. Thermogravimetric Analysis (TGA) revealed the presence of amorphous and perhaps highly functionalized carbon resulting from the partial decomposition of organic precursors, suggesting further optimization of the synthesis process is required. X-Ray Photoelectron Spectroscopy (XPS) was used to analyze the near surface composition, while the electrochemical activity towards ORR was measured by Rotating Disk Electrode (RDE) in alkaline electrolyte. The effect of dopant atoms, including the influence of different transition metal atoms, on the physical and chemical characteristics of carbon particles is also discussed. Figure 1: (a) Photograph of RSDT deposition process for synthesizing doped nanocarbons for catalytic applications, (b) schematic and (c) BF TEM image showing structure of Fe, N doped carbon aggregates. The chemical and structural characterization of the primary particles using (d) XPS and (e) HRTEM, and (f) Raman spectroscopy, highlighting the influence of dopant elements Fe and N in controlling the structure of RSDT synthesized carbon.

Iron–Nitrogen-Doped Dendritic Carbon Nanostructures for an Efficient Oxygen Reduction Reaction

A novel Fe–N-doped carbon with a dendritic structure is analyzed as an electrocatalyst for the oxygen reduction reaction. The synthesis of the material was accomplished through a nanocasting approa...

Ancient Chemistry “Pharaoh’s Snakes” for Efficient Fe-/N-Doped Carbon Electrocatalysts

The method of fabricating nonprecious metal electrocatalysts with high activity and durability through a facile and eco-friendly procedure is of great significance to the development of low-cost fuel cells and metal-air batteries. Herein, we present that an ancient chemical reaction of "Pharaoh's snakes" can be a fast and convenient technique to prepare Fe-/N-doped carbon (Fe/N-C) nanosheet/nanotube electrocatalysts with sugar, soda, melamine, and iron nitrate as precursors. The resultant Fe/N-C catalyst has a hierarchically porous structure, a large surface area, and uniformly distributed active sites. The catalyst shows high electrocatalytic activities toward both the oxygen reduction reaction with a half-wave potential of 0.90 V (vs reversible hydrogen electrode) better than that of Pt/C and the oxygen evolution reaction with an overpotential of 0.46 V at the current density of 10 mA cm-2 comparable to that of RuO2. The activity and stability of the catalyst are also evaluated in primary and rechargeable Zn-air batteries. In both conditions, three-dimensional Fe/N-C exhibited performances superior to Pt/C. Our work demonstrates a success of utilizing an ancient science to make a state-of-the-art electrocatalyst.

SiO2-protected shell mediated templating synthesis of Fe–N-doped carbon nanofibers and their enhanced oxygen reduction reaction performance

An effective SiO2-protecting pyrolysis method for the synthesis of highly active meso/microporous Fe–N-CNF catalysts is presented.

Molybdenum carbide promotion on Fe-N-doped carbon nanolayers facilely prepared for enhanced oxygen reduction.

The catalysts towards the oxygen reduction reaction (ORR) are the key materials for fuel cells and have stimulated continuous investigations on rational designs. Apart from the popular strategies reported, we demonstrate here a facile method resulting in a nanocomposite composed of molybdenum carbide (Mo2C) nanoparticles embedded and buried in Fe-N-doped carbon nanolayers by directly pyrolyzing the mixture of Fe2(MoO4)3 and dicyandiamide. The underlying Mo2C donates electrons of higher energy to the exterior N-containing carbon nanolayers (NC) and strongly couples with the active sites induced by Fe in the NC layer, leading to significant improvement at half-wave potential with respect to the control sample without Mo2C. The catalyst as a whole exhibits a fairly good ORR performance comparable to commercial Pt/C. Moreover, the method is extremely simplified and the material shows better long-term stability and tolerance to the methanol crossover in comparison with Pt/C.

Monodisperse Copper Nanoparticles on Porphyrin-Derived Fe–N-Doped Carbon for Hydrogen Generation from Ammonia Borane

Monodisperse Copper Nanoparticles on Porphyrin-Derived Fe–N-Doped Carbon for Hydrogen Generation from Ammonia Borane

Space-Confined Pyrolysis for the Fabrication of Fe/N/C Nanoparticles as a High Performance Oxygen Reduction Reaction Electrocatalyst

In this manuscript, we develop a novel method based on the combination of space-confined pyrolysis and second heat-treatment for the synthesis of Fe/N-doped Carbon (Fe/N/C) ORR catalyst, targeting solving the low yield, insufficient nitrogen-doped level, and nanostructure collapse problems. The silica-confined space is constructed by covering an outer inorganic silica layer onto the surface Fe/Phenanthroline/C (Fe/Phen/C) precursor. Within this silica-confined space, the precursor loss, particle coagulation and structure collapse that are commonly encountered during high-temperature pyrolysis in an open system can be eliminated. Moreover, the porosity and nitrogen-doped configuration can further be tuned by a second heat-treatment process. The resultant Fe/N/C catalyst show excellent ORR activity in alkaline media, better durability and stronger methanol tolerance compared to those of state-of-the-art Pt/C catalyst.

Fe–N-Doped carbon foam nanosheets with embedded Fe2O3 nanoparticles for highly efficient oxygen reduction in both alkaline and acidic media

We report a high performance oxygen reduction reaction (ORR) electrocatalyst Fe2O3@Fe–N–C, which is composed of Fe–N-doped carbon foam nanosheets with embedded carbon coated Fe2O3 nanoparticles to enhance the ORR performance in both alkaline and acidic media.

Three-dimensional porous metal–nitrogen doped carbon nanostructure as a superior non-precious electrocatalyst in oxygen reduction reaction

We report the porous transition metal–nitrogen doped carbon nanostructures as cathode catalysts using a well-stacked arrangement of template materials in the presence of polyvinylpyrrolidone as nitrogen and carbon sources and metal phthalocyanine as metal and nitrogen sources. The as-prepared nanostructures show high specific surface areas (105.73–228.13m2g−1), porous structure, and doped metal and nitrogen species (pyridinic-N, pyrrolic-N, and graphitic-N) into carbon structures. In particular, the porous Fe–N-doped carbon nanostructure exhibits excellent ORR electrocatalytic properties in alkaline electrolyte; i.e., electron transfer number close to 4, high half-wave potential (0.81V), improved electrochemical stability (a slight decrease of ∼31mV in the half-wave potential after the stability test), and methanol tolerance.

Fe-N-Doped Carbon Capsules with Outstanding Electrochemical Performance and Stability for the Oxygen Reduction Reaction in Both Acid and Alkaline Conditions.

High surface area N-doped mesoporous carbon capsules with iron traces exhibit outstanding electrocatalytic activity for the oxygen reduction reaction in both alkaline and acidic media. In alkaline conditions, they exhibit more positive onset (0.94 V vs RHE) and half-wave potentials (0.83 V vs RHE) than commercial Pt/C, while in acidic media the onset potential is comparable to that of commercial Pt/C with a peroxide yield lower than 10%. The Fe-N-doped carbon catalyst combines high catalytic activity with remarkable performance stability (3500 cycles between 0.6 and 1.0 V vs RHE), which stems from the fact that iron is coordinated to nitrogen. Additionally, the newly developed electrocatalyst is unaffected by the methanol crossover effect in both acid and basic media, contrary to commercial Pt/C. The excellent catalytic behavior of the Fe-N-doped carbon, even in the more relevant acid medium, is attributable to the combination of chemical functions (N-pyridinic, N-quaternary, and Fe-N coordination sites) and structural properties (large surface area, open mesoporous structure, and short diffusion paths), which guarantees a large number of highly active and fully accessible catalytic sites and rapid mass-transfer kinetics. Thus, this catalyst represents an important step forward toward replacing Pt catalysts with cheaper alternatives. In this regard, an alkaline anion exchange membrane fuel cell was assembled with Fe-N-doped mesoporous carbon capsules as the cathode catalyst to provide current and power densities matching those of a commercial Pt/C, which indicates the practical applicability of the Fe-N-carbon catalyst.

Non-precious Mn1.5Co1.5O4–FeNx/C nanocomposite as a synergistic catalyst for oxygen reduction in alkaline media

A nanocomposite material containing non-precious bimetal oxides and FeN-doped carbon was synthesized with double synergistic effect for ORR.

Synthesis of nanoporous structured iron carbide/Fe–N–carbon composites for efficient oxygen reduction reaction in Zn–air batteries

An iron carbide-embedded Fe–N-doped carbon catalyst with high-performance for oxygen reduction in Zn–air batteries was prepared through a facile and effective strategy.