Hybrid of Fe@Fe3O4 core-shell nanoparticle and iron-nitrogen-doped carbon material as an efficient electrocatalyst for oxygen reduction reaction

Novel and Green Synthesis of Nitrogen-Doped Carbon Cohered Fe3O4 Nanoparticles with Rich Oxygen Vacancies and Its Application

A one-pot and green synthesis methodology was successfully designed to prepare nitrogen-doped carbon (NC) cohered Fe3O4 nanoparticles with rich oxygen vacancies (Fe3O4-OVs/NC). The preparation was achieved via cold-atmospheric-pressure air plasma using Fe2O3 nanoparticles as the only precursor, and pyridine as the carbon and nitrogen source. Systematic characterization results of the as-prepared Fe3O4-OVs/NC confirmed the transition from Fe2O3 to Fe3O4, along with the generation of oxygen vacancies, while preserving the original needle-like morphology of Fe2O3. Moreover, the results indicated the formation of the NC attaching to the surface of the formed Fe3O4 nanoparticles with a weight percent of ~13.6%. The synthesized nanocomposite was further employed as a heterogeneous Fenton catalyst to remove phenol from an aqueous solution. The material has shown excellent catalytic activity and stability, demonstrating a promising application for wastewater treatment.

Fe/N-doped hollow porous carbon spheres for oxygen reduction reaction

Herein, we design a dual-template-assisted pyrolysis method to prepare ultra-small Fe₃O₄ nanoparticles anchored on Fe/N-doped hollow porous carbon spheres (0.010-Fe/NHPCS-800) for oxygen reduction reaction (ORR). The synthesized SiO₂ nanospheres, which are selected as the hard template, contribute to forming macroporous structure. Pluronic ® F127 is employed to fabricate mesopores through high-temperature pyrolysis as a soft template. In this way, the 0.010-Fe/NHPCS-800 architecture represents an ordered hierarchically porous property with a large BET surface area (1812 m² g^-1), which can facilitate the mass transport of reactants and increase the electrochemically active area. The Fe₃O₄ nanoparticles wrapped by graphitic carbon layers provide more active sites, and the synergistic interaction between Fe₃O₄ nanoparticles and doping N has a positive effect on ORR performance. The 0.010-Fe/NHPCS-800 catalyst outperforms the most effective ORR activities among a series of Fe/NHPCS samples with onset potential of 0.95 V (versus reversible hydrogen potential) and half-wave potential of 0.81 V, which is almost the same as the commercial Pt/C (0.96 and 0.81 V, correspondingly) in 0.10 M KOH. However, both the stability and durability of 0.010-Fe/NHPCS-800 surpass those of commercial Pt/C. Given all these advantages, 0.010-Fe/NHPCS-800 is a promising candidate to take the place of Pt-based electrocatalysts for ORR in the future.

NH3-Plasma pre-treated carbon supported active iron–nitrogen catalyst for oxygen reduction in acid and alkaline electrolytes

A new strategy in the synthesis of M–N–C type catalysts was introduced through the combination of plasma pre-treatment followed by conventional pyrolysis, which demonstrated higher ORR activity and stability than pristine M–N–C catalysts.

Green synthesis of nitrogen-doped self-assembled porous carbon-metal oxide composite towards energy and environmental applications

Increasing environmental pollution, shortage of efficient energy conversion and storage devices and the depletion of fossil fuels have triggered the research community to look for advanced multifunctional materials suitable for different energy-related applications. Herein, we have discussed a novel and facile synthesis mechanism of such a carbon-based nanocomposite along with its energy and environmental applications. In this present work, nitrogen-doped carbon self-assembled into ordered mesoporous structure has been synthesized via an economical and environment-friendly route and its pore generating mechanism depending on the hydrogen bonding interaction has been highlighted. Incorporation of metal oxide nanoparticles in the porous carbon network has significantly improved CO₂ adsorption and lithium storage capacity along with an improvement in the catalytic activity towards Oxygen Reduction Reaction (ORR). Thus our present study unveils a multifunctional material that can be used in three different fields without further modifications.

Three-Dimensional Multi-Doped Porous Carbon/Graphene Derived from Sewage Sludge with Template-Assisted Fe-pillared Montmorillonite for Enhanced Oxygen Reduction Reaction

Three-dimensional multi-doped porous carbon/graphene (Fe-Mt-SS-C) was prepared by carbonization of sewage sludge with template-assisted Fe-pillared montmorillonite. The material consisted of nanosheet- and particle- carbon had a high specific surface area (784.46 m²·g⁻¹) and hierarchical porous structure of micro-, meso- and macropores. The prepared Fe-Mt-SS-C had a high degree of graphitization and large amount of defect atoms. The pyrolysis process made full use of the C, N, Fe, and S by turning them into the carbon framework of the as-obtained material in situ. Template-assisted Fe-pillared montmorillonite contributed to more characteristics of morphology and composition on Fe-Mt-SS-C than other three materials (SS-C, Mt-SS-C and Fe-SS-C), and enhanced the electrocatalytic ORR activity by providing more adsorption sites and the electronic structure, resulting in the increase of conductivity and electrochemical activity. The ORR activity performance of Fe-Mt-SS-C, including the value of onset potential (0.03 V) and E_1/2 (−0.09 V), was better than that of commercial 20 wt% Pt/C (−0.02 V and −0.18 V, respectively). Moreover, the Fe-Mt-SS-C possessed excellent durability and outstanding immunity toward methanol crossover effects. Therefore, the resultant Fe-Mt-SS-C has great potential to applied as a high-efficiency ORR electrocatalyst, more importantly, it realizes the utilization of the sludge at the same time.

Hollow Nitrogen-Doped Carbon Spheres with Fe3O4 Nanoparticles Encapsulated as a Highly Active Oxygen-Reduction Catalyst

The development of nonprecious electrocatalyst with low cost and high efficiency for the oxygen reduction reaction (ORR) is a main challenge for electrochemical energy technology. In this work, a hierarchical hollow core-shell structured N-doped carbon spheres (N-HSCS), in which Fe₃O₄ nanoparticles are encapsulated (Fe₃O₄/N-HCSC) has been successfully prepared. The Fe₃O₄/N-HCSC electrocatalyst exhibits a remarkable catalytic performance toward ORR. The porous hollow core-shell structure and synergistic effect between Fe₃O₄ and protective nitrogen-doped graphitic layers are mainly responsible for such an excellent ORR catalytic property and stability. This work demonstrates a promising strategy of nanostructure-engineering to the future design and preparation of highly efficient non-noble metal electrocatalysts.

Superiority of boron, nitrogen and iron ternary doped carbonized graphene oxide-based catalysts for oxygen reduction in microbial fuel cells

The exploration of highly active and cost-effective catalysts for the oxygen reduction reaction is vitally important to facilitate the improvement of metal-air batteries and fuel cells. Herein, super-active catalysts made from an interesting metal-polymer network (MPN) that consist of Fe-N_x-C, B-N and Fe₃O₄/Fe₃C alloys were prepared via facile one-pot carbonization. The achieved catalysts possessed an amazing porous structure that was derived from the MPN with the assistance of a "bubble-template". Remarkably, the content of highly active Fe-N_x-C can be regulated by introducing graphene, and the ORR activity of the catalyst was enhanced dramatically with an increase in the Fe₃O₄/Fe₃C alloy content. The most active BNFe-C-G2 catalyst exhibited superior ORR activity/stability, and was then employed as an air cathode electrocatalyst in a microbial fuel cell. The results showed that the output voltage and power density of BNFe-C-G2 were significantly improved to 575 ± 11 mV and 1046.2 ± 35 mW m^-2, respectively. These values are 4.5% and 44.44% higher than those of commercial Pt/C. Thus, due to the synergistic electrocatalysis of the Fe-N_x-C, B-N and Fe₃O₄/Fe₃C alloys, the super-active and low-cost BNFe-C-G2 material should be a promising ORR catalyst for application in biofuel cells, and in many other energy conversion and storage devices.

Microwave-assisted synthesis and prototype oxygen reduction electrocatalyst application of N-doped carbon-coated Fe3O4 nanorods

Fe₃O₄ nanorods coated with nitrogen-doped mesoporous carbon (ND-Fe₃O₄@mC) shells of defined thicknesses have been prepared via a new microwave-assisted approach. Microstructural characterization of these ND-Fe₃O₄@mC structures was performed using x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. Following identification, the electrochemical performance of the catalysts was evaluated using linear sweep voltammetry with a rotating disc electrode system. The present investigation reveals enhanced oxygen reduction reaction catalytic activity and the carbon layer thickness influences oxygen diffusion to the active Fe₃O₄ nanorod core.

Uniformly distributed and in situ iron–nitrogen co-doped porous carbon derived from pork liver for rapid and simultaneous detection of dopamine, uric acid, and paracetamol in human blood serum

Pork liver with rich nitrogen, iron, and carbon can be transformed into an electrochemical selective sensorviaa one-step calcination method.

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.

Tuning α-Fe2O3 nanotube arrays for the oxygen reduction reaction in alkaline media

α-Fe₂O₃ nanotube arrays were fabricated and employed as low cost non-noble electrocatalysts for the oxygen reduction reaction (ORR). As-prepared α-Fe₂O₃ nanotube arrays exhibit excellent ORR catalytic activity and durability in alkaline media.