FeCo Nanoparticles Research Articles

Correlation of phase composition, magnetic properties and hyperthermia efficiency of silica-coated FeCo nanoparticles for therapeutic applications

The local atomic order, magnetic properties, hyperthermia efficiency, drug loading capacity and in-vitro cytotoxicity are investigated for the core–shell (Fe25Co75)x(SiO2)100-x (70 ≤ x ≤ 100, wt.%) nanoparticles (NPs) sintered by the metals co-precipitation followed with SiO2 TEOS deposition. Electron microscopy reveal the formation of nearly spherical structures with medium diameter from 80 nm to 220 nm containing 20–50 nm cores identified by XRD as α-FeCo bcc alloy. Mössbauer spectra and magnetometry reflects the formation of magnetically-interacting net of single-domain FeCo cores with broad size distribution. Observed decrease in magnetization (MS) and effective magnetic anisotropy (Keff) for NPs with × is the consequence of the increasing thickness of the SiO2 shells. Calculations indicate that there is an optimal thickness δ of SiO2 shells ranging between 90 ÷ 120 nm for the highest value of specific absorption rate (SAR) originating from their effect on Keff values. Experimentally proved that SAR has the highest value for (FeCo)80(SiO2)20 NPs in correlation with the Linear Response Theory approach. High drug loading capacity (up to 98%) and low in-vitro cytotoxicity (IC50 index below 230 µg/ml) experimentally proved for (FeCo)x(SiO2)100-x NPs make them perfect candidates for designing smart drug delivery systems.

Synergistic effect of selectively etched CoFe and N-doped hollow carbon spheres for high performance lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) feature benefits of high theoretical specific capacity, but they are severely constrained by the shuttle effect of lithium polysulfides and volume expansion in the process. To address these issues, CoFe nano particles covered in N-doped carbon (SE-CoFe@NC) layer were prepared by bimetallic-organic skeleton pyrolysis method and used as cathode matrix for LSBs. The nitrogen-carbon shell layer and polar CoFe-alloy nanoparticles provide plentiful chemisorption sites for polysulfides, and the alloy is essential for accelerating the redox conversion of polysulfides. Nitrogen-doped carbon layer promotes ion/electron transport and the nitrogen doping is generally considered to have a strong adsorption effect on polysulfides, with the hollow carbon spheres acting synergistically in promoting electrolyte penetration, enhancing sulfur loading capacity and accommodating sulfur expansion during cycling. Take advantage of these benefits, the S@CoFe/NC-80 composite cathode exhibits strong adsorption capability of lithium polysulfides (LiPSs), efficient reaction kinetics and stable cycling performance (reversible capacity of 617 mAh g−1 at 0.2C after 200 cycles, and when the charging/discharging rate reaches 1C, it maintains a reversible discharge capacity of 490 mAh g−1 after 1000 cycles with a per-cycle decay rate of only 0.05%). The synergistic effect of the dual properties of the catalytic activity of the CoFe alloy and the conductive hollow nitrogen-carbon layer provides a viable solution for the appropriate design of bimetallic alloy structures and promotes further applications.

Sol-gel synthesis control of iron-cobalt alloy/ferrite core/shell nanoparticles supported by a carbon medium with semi-hard magnetic features

We explore a simple and optimized approach for obtaining magnetic nanoparticle-carbon composites by a novel one-pot sol-gel method. In them, various metal cations ratios of Fe3+ and Co2+ are evaluated. The ratio of Fe:Co is a critical parameter that governs the presence of different crystalline phases with tailored magnetic properties. Interestingly, the smallest introduction of Co into the synthesis (19Fe:1Co) provides an abrupt emergence of the body-centered cubic (bcc) Fe-Co alloy, instead of the orthorhombic Pnma structure characteristic of the Fe3C intermetallic compound (1Fe:0Co). Advanced structural and electronic characterizations reveal the formation of Fe-Co/Co-ferrite core/shell nanoparticle structures embedded in a carbon matrix. The sphere-like nanoparticles range from 10 to 45 nm and the shells show a spinel structure with a thickness of 2–3 nm. In addition, X-ray absorption spectroscopy unveils that the oxidation state of Fe and Co cations is close to zero, demonstrating their predominant metallic character. The magnetic properties can be modulated by a precise control of the alloy composition varying the Co content, displaying saturation magnetization values close to ∼137 emu/g. The nanoparticles are mainly single magnetic domain with a considerable coercive field (∼450 Oe), higher than those reported in the literature for Fe-Co nanoparticles. This semi-hard character is due to a notable spring exchange effect emerged by passivating the surface of Fe-Co-bcc cores with a thin Co-ferrite-like shell.

High-valent metal site incorporated heterointerface catalysts for high-performance anion-exchange membrane water electrolysers

The design of heterointerface-structured catalysts with tunable active sites is critical to address the activity and durability challenges of water oxidation process. In this study, a novel interfacial engineering strategy based on the anionic diffusion-limited Kirkendall effect (KE) was employed for the synthesis of a FeCo/FeCoP with high-valent Fe (Fe+3.18) sites. Specifically, a model system of the FeCo/FeCoP heterointerface was obtained through the phosphidation of carbon-encapsulated FeCo nanoparticles. The highly efficient and stable oxygen evolution reaction (OER) performance of the FeCo/FeCoP catalyst was demonstrated in an anion-exchange membrane water electrolyser (12.26 A cm–2 at 2.0 V). Through density functional theory calculations, the high-valent Fe sites in the FeCo/FeCoP heterointerface were found to balance the adsorption energetics of the OER intermediates. The structure–oxidation state–OER activity correlation of the FeCo/FeCoP catalysts demonstrated herein emphasises the significance of understanding the water oxidation chemistry of heterointerface-structured catalysts for their potential applications in different energy conversion devices.

Flexible electrospun FeCo/carbon hybrid nanofiber films as binder-free anodes for enhanced lithium storage performance

The design of electrodes with excellent mechanical elasticity is the significant to developing flexible electronic devices with mechanical endurance and outstanding lithium storage properties. Herein, the flexible FeCo/carbon hybrid nanofiber membranes (named as FeCo@CNFM) were successfully prepared via electrospinning and subsequent carbonization process. From the macroscopic perspective, the FeCo@CNFM can bend at a large angle without any destruction, and be directly used as working electrode of lithium ions batteries (LIBs) without any expensive additives, demonstrating its extraordinary mechanical flexibility. From the microscopic perspective, the homogeneously dispersed fine FeCo nanoparticles and the three-dimensional (3D) interconnected transport network constructed of carbon nanofibers significantly shorten the lithium-ion transfer distance, eliminate the volume fluctuation during lithiation/delithiation process, enhance the utilization rate of active materials, and promote the electrical conductivity of the composite electrode, thus leading to remarkably improved electrochemical properties. As a consequence, the optimized FeCo@CNFM manifests a superior discharge capacity of 584.9 mA h g−1 at 100 mA g−1 after 100 cycles with long cycling stability and good rate capability of 227.1 mA h g−1 even at a large current rate of 2 A g−1, making it a promising flexible self-supporting anode for LIBs.

Role of biochar-based catalysts in microwave-induced biomass pyrolysis: Structural properties and modification with Fe-series metals

Biochar-based catalysts have great potential for microwave-induced biomass pyrolysis due to the combination of their excellent microwave absorption performance, good porous structure, and high catalytic activity. In this work, the potential of biochar-based catalysts for microwave-induced catalytic biomass pyrolysis to produce gaseous fuel and upgrade bio-oil was explored and the role of the structural characteristics and Fe-series modification was revealed. The results indicated that the catalytic performance of pure biochar was influenced by their microstructures, and the KOH-activated biochar with abundant microporous structures could effectively promote the gas yields from biomass pyrolysis under microwave heating conditions. With the loading of Fe0 crystal nanoparticles on biochar, the catalytic activity of biochar was greatly enhanced, resulting in an increase in combustible gas (CO, H2 and CH4) yield by 50 % compared to pure biochar, reaching 502.09 mL/g at 650 °C, as well as significant simplification of the bio-oil. Furthermore, the Fe-series alloy crystals exhibit superior catalytic activity over Fe0, further improving gas yields and promoting bio-oil upgrading. The biochar loading of Fe0.64Ni0.36 nanoparticles resulted in a combustible gas yield as high as 574.84 mL/g, and the production of hydrocarbons was greatly enhanced, with a high relative content of 33.9 % in bio-oil. Biochar-based CoFe nanoparticles promoted selective production of H2, with a yield as high as 230.84 mL/g, and the content of mono-phenols in the bio-oil was improved to 74.0 % with the composition of a high phenol relative content of 17.508 %, a trans-isoeugenol relative content of 17.260 %, and a guaiacol relative content of 12.780 %.

The bifunctional 3D-on-2D FeCo/Ni(OH)2 hierarchical nanocatalyst for industrial-level electrocatalytic water splitting

Developing high-performing and cost-effective bifunctional electrocatalysts under the industrial conditions is significant for revolutionizing the hydrogen economy. Herein, we developed a bifunctional 3D-on-2D FeCo/Ni(OH)2 hierarchical nanocatalyst on Ni mesh by a facile and low-cost method that can boost both the two half-reactions of water splitting all at once. The FeCo/Ni(OH)2/Ni mesh showed an outstanding electrocatalytic performance under the industrial conditions (3 M KOH, 90 °C) with applied voltages of 1.47 and 1.91 V to drive the electrolyzer at 10 and 500 mA/cm2, respectively, much better than the Ni(OH)2/Ni mesh, FeCo/Ni mesh, and Raney Ni/Ni mesh samples. Furthermore, it can maintain good stability for more than 192 h under the working condition of 500 mA/cm2. This promotion in electrocatalytic properties can be ascribed to the synergistic effects between 3D FeCo nanoparticles and 2D Ni(OH)2 nanosheets, including the large electrochemically active surface areas, the intense electronic interplay between the two component and the elevated interfacial contact and charge transport. Eventually, this water electrolyzer yields a 14.7% solar-to-hydrogen efficiency when integrated with Si solar cells, which exceeds analogous solar-driven systems reported so far.

Confined Diffusion Strategy for Customizing Magnetic Coupling Spaces to Enhance Low‐frequency Electromagnetic Wave Absorption

AbstractThe rational design of magnetic composites has great potential for electromagnetic (EM) absorption, particularly in the low‐frequency range of 2–8 GHz. However, the scalable synthesis of such magnetic absorbers with both high magnetic content and good dispersity remains challenging. In this study, a confined diffusion strategy is proposed to fabricate functional magnetic‐carbon hollow microspheres. Driven by the ferromagnetic enhanced Kirkendall diffusion effect, the in situ alloying of FeCo nanoparticles is tightly confined in carbon shells, effectively inhibiting magnetic agglomeration. Moreover, the core–shell FeCo–carbon nano‐units further assemble into dispersive microscale magnetic‐carbon Janus bulges on both the inner and outer surfaces of the hollow microsphere. The optimized hollow FeCo@C microspheres exhibit excellent low‐frequency EM wave absorption performance: the minimum reflection loss (RLmin) is −35.9 dB, and the absorption bandwidth covers almost the entire C‐band. Systematic investigation reveals that the large size of the magnetic‐carbon integration, high–density confined magnetic units, and strong magnetic coupling are essential for enhancing the magnetic loss dissipation of low‐frequency EM waves. This study provides a novel strategy for fabricating advanced EM wave absorbers and significant inspiration for investigating the magnetic attenuation mechanism at low frequency.

Entropy production on couple-stress hybrid nanofluid flow in a rocket engine nozzle with non-Fourier’s and non-Fick’s law

At the industrial level, hybrid nanofluid plays a significant role in innovative technologies and engineering expedients. The current investigation focused on assessing heat and mass relocation concerned with the flow of a couple-stress hybrid nanofluid in a rocket engine nozzle with non-Fourier’s and non-Fick’s law. The amalgamation of spherical-shaped nanoparticles of CoFe 2 O 4 and MWCNT suspended in engine oil (ordinary fluid) are considered hybrid nanofluids. This study is unique because it includes entropy generation, viscous dissipation, thermal radiation, Thomson and Troian, thermal, and concentration slips. From the intended problem, the obtained partial differential equations were transfigured into ordinary differential equations with the help of resemblance conversion and then solved by bvp4c. The significant effects of influential physical parameters are investigated and presented by graphs and tables. The result shows that an increment in the couple-stress parameter upsurges the velocity of the fluid and entropy generation. An increase in the Thomson and Troian slip parameters, on the other hand, results in a decrease in the fluid’s velocity. Also, it is observed from the result that an increment in the thermal relaxation parameter reasons a decline in temperature distribution. Likewise, it is noticed from the study that the highest enhancement of heat relocation rate happens at a ( CoFe 2 O 4 + MWCNT ) nanoparticles volume fraction of 4 % (i.e. 66.12 % of the CoFe 2 O 4 nanoparticles). Also, the Brinkman number needs to be well-organized to minimize entropy production in the system.

A simple antigen-antibody reaction using ultrasmall FeCo nanoparticles

In this study, we prepared ultrasmall FeCo nanoparticles (NPs) with a high magnetic moment and examined their antigen-antibody reaction for biodetection applications. The FeCo NPs were collected from the FeCo-BaF2 nanogranular film with Fe:Co:Ba:F = 14:11:21:54 at.%, by dissolving the film in water since the BaF2 matrix was deliquescent. The size of FeCo NPs was ∼5 nm and the saturation magnetization was estimated to be ∼15.30 kG (149.0 emu/g). The Candida albicans antibodies (abcam ab53891)-conjugated FeCo NPs were collected by using an ultracentrifugal separation (110 000 rpm, 90 min), they were then reacted with Candida albicans. The obtained result indicates that Candida albicans were absorbed successfully onto FeCo NPs, and the number of Candida albicans bound to FeCo NPs counted from the micrographs of the aggregates of FeCo NPs and Candida albicans increased significantly by adding sonication treatment of the film in water before binding them to the antibodies. The success of antigen-antibody reaction of ultrasmall NPs with high magnetic moment improves detection sensitivity as well as offers potential detection for smaller biomolecules.

Study of the radar absorption of metal-carbon nanocomposites (review)

Development of the technology for the synthesis of magnetic nanoparticles of metals and alloys has opened up the possibility of their use in the field of radar-absorbing materials (RAM). The results of studying the properties of nanocomposites, method for the synthesis of metal-carbon nanocomposites by pyrolysis using infrared heating are reviewed. The magnetic, electromagnetic, and radar-absorbing properties of the obtained nanocomposites depending on the synthesis temperature and metal concentration were studied. It is shown that the chosen metals, alloys (FeCo) and carbon material are effective for isolating magnetic nanoparticles when developing hybrid radar-absorbing composites. Moreover, methods for controlling the radar-absorbing properties of hybrid composites and the prospects for improving the impedance matching are considered. An analysis of the efficiency of absorption of electromagnetic radiation by FeCo/C nanocomposites synthesized by different methods is presented. The possibility of controlling the morphology and properties of metal-carbon nanocomposites using certain approaches to synthesis, varying the compositions of precursors, and the orientation of FeCo nanoparticles synthesized in the form of flakes in the composite has been revealed. The results of the study can be used to improve the technique of using FeCo/C nanocomposites obtained by pyrolysis of organometallic precursors based on polyacrylonitrile in the field of radar-absorbing materials.

Effect of alkaline activation on the structural characteristics of nanocomposites based on carbonized chitosan and Fe-Co bimetallic nanoparticles

Metal-carbon nanocomposites consisting of Fe-Co bimetallic nanoparticles uniformly dispersed in the carbon matrix were synthesized by pyrolysis of a precursor based on chitosan and metal salts in the temperature range 500-800°C. The change in the structural characteristics of the samples after activation in the presence of potassium hydroxide was studied. It was found that alkaline activation leads to an increase in the specific surface area of the nanocomposites up to 700 m2/g and in the size of metal nanoparticles, whereas the phase composition and morphology of the carbon support remain unchanged.

FeCo/Graphene Nanocomposites for Applications as Electromagnetic Wave-Absorbing Materials

Simple and efficient preparation high-performance magnetic carbon-based nanocomposites as electromagnetic wave-absorbing materials is a research hotspot. Here, employing a straightforward, ecologically friendly, and effective solid-state technique, FeCo/graphene nanocomposites with good electromagnetic wave absorption capabilities were successfully fabricated without the use of any external carbon sources. m-NaCl powder is combined with Co(acac)2 and Fe(acac)3 and then annealed at a particular temperature. During the annealing process, FeCo nanoparticles were synthesized and supported on graphene nanocomposites. Following annealing at 700 °C, the material showed an ideal reflection loss of −71.63 dB at 10.8 GHz, an effective bandwidth of 4.24 GHz, and a thickness of 2.68 mm. The radar cross section (RCS) of FeCo/C-700 is less than −10 dB m2, which provides evidence that the samples have good radar wave attenuation capabilities when the scattering angle is between 0 and 60°. The approach for creating graphene composites with FeCo nanoparticles suggested in this study serves as a crucial source of inspiration for the later development of new magnetic carbon nanocomposite systems.

Facile synthesis of FeCo–MnO2 core–shell nanoparticles as high-frequency microwave absorbers using a two-step method

The absorption performance of Fe80Co20 (FeCo) nanoparticles for electromagnetic waves is diminished by their low complex permittivity. The complex permittivity of FeCo nanoparticles can be easily tuned by combining the nanoparticles with dielectric materials. A MnO2 shell has a porous structure, and its pore size increases with increasing thickness, resulting in enhanced impedance matching and multiple scattering within pores. Herein, FeCo–MnO2 core–shell nanoparticles with different MnO2 shell thicknesses were synthesized using a polyol-coating method. Their imaginary permeability was almost constant regardless of the MnO2 shell thickness, whereas their complex permittivity increased with increasing MnO2 shell thickness. The FeCo–MnO2 (71 nm) nanoparticles showed Lorentz-type dielectric resonance due to a displacement current lag at a core–shell interface. The FeCo–MnO2 (71 nm) nanoparticles showed a high reflection loss of –36 dB at 17 GHz, wide bandwidth of 4.9 GHz, and microwave absorber thickness of 1.9 mm. The mechanisms responsible for microwave absorption were magnetic coupling, natural resonance, interfacial polarization, Lorentz type resonance, hopping, and multiple scattering. This strategy enables the easy and practical design of magnetic core–dielectric shell-based microwave absorbers.

N,S-co-doped FeCo Nanoparticles Supported on Porous Carbon Nanofibers as Efficient and Durable Oxygen Reduction Catalysts.

Finding high-performance, low-cost, efficient catalysts for oxygen reduction reactions (ORR) is essential for sustainable energy conversion systems. Herein, highly efficient and durable iron (Fe) and cobalt (Co)-supported nitrogen (N) and sulfur (S) co-doped three-dimensional carbon nanofibers (FeCo-N, S@CNFs) were synthesized via electrospinning followed by carbonization. The as-prepared FeCo-N,S@CNFs served as efficient ORR catalysts in alkaline 0.1 m KOH solutions that were N2 and O2 -saturated. The experimental results revealed that FeCo-N,S@CNFs were highly active ORR catalysts with defect-rich active pyridinic N and pyrrolic N and metal bonds to N and S atom sites, which enhanced the ORR activity. FeCo-N,S@CNFs exhibited a high onset potential (Eonset =0.89 V) and half-wave potential (E1/2 =0.85 V), similar to the electrocatalytic activity of commercial Pt/C. Additionally, the durability of the as-prepared FeCo-N,S@CNFs catalysts was maintained for 14 h with long-term stability and high tolerance to methanol stability, accounting for their excellent catalytic ability. Furthermore, Co-N@CNFs, Fe-N@CNFs, and varying Fe and Co ratios were compared with those of FeCo-N,S@CNFs. Synergistic interactions between metals and heteroatoms were believed to play a significant role in enhancing the ORR activity. Owing to their excellent catalytic reduction ability, the as-prepared FeCo-N,S@CNFs can be widely used in battery-based systems and replace commercial Pt/C in fuel cell applications.

Preparation of FeCo/C-N and FeNi/C-N Nanocomposites from Acrylamide Co-Crystallizates and Their Use as Lubricant Additives.

FeCo and FeNi nanoalloy particles encapsulated in a nitrogen-doped carbonized shell (FeCo/C-N and FeNi/C-N) were synthesized by thermolysis at 400 °C of polyacrylamide complexes after frontal polymerization of co-crystallizate of Fe and Co or Ni nitrates and acrylamide. During the thermolysis of polyacrylamide complexes in a self-generated atmosphere, Co(II) or Ni(II) and Fe(III) cations are reduced to form FeCo and FeNi nanoalloy particles, while polyacrylamide simultaneously forms a nitrogen-doped carbon shell layer. This unique architecture provides high chemical and thermal stability of the resulting nanocomposites. The average crystallite size of FeCo and FeNi nanoparticles is 10 and 12 nm, respectively. The nanocomposites were studied by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The nanocomposites have been tested as antifriction and antiwear additives in lubricating oils. The optimal concentrations of nanoparticles were determined, at which the antifriction and antiwear properties of the lubricant manifest themselves in the best possible way.

Fabrication of FeCo/Multidimensional Carbon-Based Nanocomposites as Excellent Cathodic Catalysts of Zn-Air Battery

Zn-air battery, like other electrochemical power devices such as fuel cells, has the advantages of environmental friendliness and high energy convert efficiency. One of the main problems facing Zn-air battery is how to improve the electrocatalytic activity of the cathode catalyst with low cost and simple preparation process. Herein, N-doped carbon nanosheets/nanotubes composite loaded Fe-Co nanoparticles were prepared via a facile pyrolysis of the solid mixture composed of dicyandiamide, sucrose, cobalt nitrate, iron nitrate, iron phthalocyanine (FePc) and cobalt phthalocyanine (CoPc). The samples were well characterized and their electroactivity towards oxygen reduction reaction (ORR) was tested in a full pH range including acidic, neutral and alkaline media. In 0.1 mol l−1 KOH solution, the ORR onset potential and half-wave potential of the FeCo-FePc/NTu-CNsh are 1.03 V and 0.91 V, which are very close to the performance of commercial Pt/C catalyst (40%). In neutral solution (1 M KCl+4 M NH4Cl), FeCo-FePc/NTu-CNsh presents an ORR onset potential of 0.93 V and half-wave potential of 0.82 V, which are superior to Pt/C with onset potential of 0.92 V and half-wave potential of 0.81 V. The home-made Zn-air battery with the prepared samples as the cathodic catalysts reveal excellent performance, and the FeCo-FePc/NTu-CNsh Zn-air battery presents a maximum power density of 281.8 mW·cm−2 as well as the high stability at different discharging current densities.

Self-standing CoFe embedded nitrogen-doped carbon nanotubes with Pt deposition through direct current plasma magnetron sputtering for direct methanol fuel cells applications

Herein, ultra-low amount Pt is uniformly deposited on the surface of CoFe nanoparticles (NPs) embedded nitrogen-doped carbon nanotubes which are grown directionally on the surface of carbon fiber cloth (Pt–CoFe@NCNT/CFC) using the direct current plasma magnetron sputtering (DC-PMS) technique. The designed electrode exhibits excellent trifunctional catalytic activities towards oxygen reduction reaction (ORR) (in 0.1 M KOH, E1/2 = 0.807 V; in 0.5 M H2SO4, E1/2 = 0.723 V), hydrogen evolution reaction (HER) (in 1 M KOH, η10 = 17 mV and η100 = 93 mV; in 0.5 M H2SO4, η10 = 42 mV and η100 = 100.5 mV) and methanol oxidation reaction (MOR) (in 0.5 M H2SO4 + 0.5 M CH3OH, peak current density reaches 115 mA mg−1Pt@1.116 V). It is verified that the DC-PMS technique can greatly improve the utilization efficiency of Pt, so as to reduce the dosage of Pt, and shows better catalytic performance and excellent stability than the commercial Pt/C catalysts. The rich hierarchical heterostructures of the designed electrode can provide more non-noble metal active sites, so as to enhance the catalytic activity and further cut down the consumption of noble metals. Impressively, Pt–CoFe@NCNT/CFC electrode assembled direct methanol fuel cell achieved a remarkable maximum power density of 73.41 mW cm−2 and shows excellent stability.

In-situ exsolution of bimetallic CoFe nanoparticles on (La,Sr)FeO3 perovskite: Its effect on electrocatalytic oxidative coupling of methane

This study presents in-situ reduction of lanthanum strontium cobalt ferrite (LSCF) perovskite as an effective method for modifying its surface properties and enhancing its electrocatalytic reactivity for oxidative coupling of methane (OCM). The evolution of hetero-phases during the reduction of LSCF resulted in CoFe nanoparticles being formed at the surface. The in-situ reduced LSCF cell for OCM could be operated in either an ion pump or a fuel cell mode. High selectivity of 63% and 10.2% were reported for C2+ hydrocarbons and C3H6, respectively. DFT calculations on LSCF and CoFe revealed that the high selectivity of C2+ hydrocarbons on the LSCF primarily stems from the presence of CoFe nanoparticles. In-situ DRIFTS conducted under CH4 proved that complete oxidation of CH4 can be effectively inhibited by reducing LSCF, and control of oxygen supply is an important parameter for selective conversion of CH4 to higher order hydrocarbon.

Schiff-base polymer derived FeCo-N-doped porous carbon flowers as bifunctional oxygen electrocatalyst for long-life rechargeable zinc-air batteries

Rational design and exploration of low-cost and robust bifunctional oxygen electrocatalysts are vitally important for developing high-performance zinc-air batteries (ZABs). Herein, we reported a facile yet cost-efficient approach to construct a bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electrocatalyst composed of N-doped porous carbon nanosheet flowers decorated with FeCo nanoparticles (FeCo/N-CF). Rational design of this catalyst is achieved by designing Schiff-base polymer with unique molecular structure via hydrogen bonding of cyanuramide and terephthalaldehyde polycondensate in the presence of metal cations. It exhibits excellent activity and stability for electrocatalysis of ORR/OER, enabling ZAB with a high peak power density of 172 mW cm−2 and a large specific capacity of 811 mA h g−1Zn at large current. The rechargeable ZAB demonstrates excellent durability for 1000 h with slight voltage decay, far outperforming a couple of precious Pt/Ir-based catalysts. Density functional theory (DFT) calculations reveal that high activity of bimetallic FeCo stems from enhanced O2 and OH− adsorption and accelerated O2 dissociation by OO bond activation.