Carbon-coated Nanoparticles Research Articles

Preparation of N, S doped Co-Fe/C catalyst derived from ZIF-67/ionic liquid and its catalytic activity for oxygen reduction reaction in alkaline electrolyte

ZIF-67(CoFe) was synthesized using the solvothermal method, and the precursor of ZIF-67(CoFe)/xC-yIL was obtained by grinding the mixture of ZIF-67(CoFe), [BMIM][NTf2] ionic liquid (IL), and carbon black. A series of ZIF-67(CoFe)/xC-yIL-T catalysts were prepared by calcining the precursor at different temperatures. The structure of the catalysts was examined using XRD, TEM, BET and XPS analysis. The results show that the high-temperature treatment of the precursor contributes to the formation of the structure of the N, S-co-doped carbon-coated nanoparticles. The introduction of ionic liquid increases the specific surface area of the catalysts and exposes more active sites. At the same time, as a sulfur source, ionic liquid forms a C-S bond, which is conducive to improving ORR activity. The optimal ORR half-wave potential and limited current density of ZIF-67(CoFe)/1.5 C-45IL-600 are 0.87 V vs. RHE and 4.64 mA cm-2, respectively, in 0.1 mol L−1 KOH.

Improved Activity and Durability of Carbon-Coated Pd and PdNi Anode Catalysts in AEMFC

Anion exchange membrane fuel cells (AEMFC) have received growing attention due to the strategic potential of using low content (or absence) of PGM catalysts in the electrodes.[1] Completely PGM-free cathode catalysts are well established in those conditions,[2] while the anode ones remain critical in terms of the beginning-of-life activity and long-term performance.[3] The widely Pt- and Pd-based catalysts degrade mainly by nanoparticles detachment and agglomeration in alkaline conditions.[4] These degradations may be slowed down by wrapping the nanoparticles in some carbon layers (called carbon-coated), that prevent also metal oxidation and leaching into the electrolyte in the RDE setup.[5] However, the performance in AEMFC of carbon-coated nanoparticle catalysts is still unclear.Here, two groups (previously characterized in RDE, XRD, IL-TEM, XPS and ICP-MS techniques[5]) of carbon-coated catalysts were investigated in 5 cm2 AEMFC: monometallic Pd (Pd@C/C) and bimetallic PdNi (PdNi@C/C) nanoparticles supported on carbon, and compared them to unprotected ones (Pd/C and PdNi/C). The four different anode catalysts were compared for a fixed Pd anode loading of 0.27 mgPd cm-2, and were combined with a ZIF-8 derived Fe-N-C cathode catalyst (previously developed Fe0.5-NH3). The Pd@C/C and PdNi@C/C reached superior initial performances (700 and 1300 mA cm-2) than the Pd/C and PdNi/C references (300 and 390 mA cm-2) at 0.6 V and Tcell = 60 °C. This translates into an initial activity trend of PdNi@C/C > PdNi/C > Pd@C/C > Pd/C. After 12 h durability test at a cell voltage of 0.3 V, the AEMFC with the PdNi@C/C based anode exhibits a dramatically higher retention of performance (95%) than the cells with Pd/C (55%) and PdNi/C (70%) anodes. These results evidence the robustness of bimetallic carbon-coated nanoparticle catalysts for AEMFC anodes. Figure 1

Special issue and perspective on the chemistry and physics of carbonaceous particle formation

Carbonaceous particles formed during the partial oxidation of a fuel constitute a primary pollutant (i.e., soot) impacting human health and the environment. The competing soot formation and oxidation pathways associated with fossil fuels and carbon-containing renewable fuels must be understood to support the development of energy-conversion devices that limit health and environmental impacts. Such knowledge is also helpful in optimizing the properties of carbon black and other carbonaceous materials used in major industrial manufacturing processes, such as graphene, nanotubes, and (functional) carbon-coated nanoparticles. The current Special Issue comprises 16 articles that highlight progress relevant to carbonaceous particles.

The Behavior of Carbon-Coated Nanoparticles in Oxidizing and Reducing Gas Environment in Environment TEM (E-TEM) Mode

The idea of a carbon-coated nanoparticles for electrochemical catalysis is not new and was widely used in direct methanol fuel cell (DMFC) [1], since the carbon coating acts as a barrier to prevent severe oxidation, thus protecting the nanoparticles from detrimental and irreversible degradation/corrosion. Recently, this type of catalyst was demonstrated to show excellent durability towards hydrogen oxidation and evolution reactions (HOR and HER), but also oxygen evolution and reduction reactions (OER and ORR), both in acid and (especially) in alkaline environment. For example, in alkaline media, Gao et. al and Doan et. al did show the excellent performance of carbon-coated Ni nanoparticles in both HOR and HER, vs. non-coated Ni; the latter degraded quickly because of severe oxidation/passivation or severe hydride poisoning. [2,3] In this work, we synthesize carbon-coated Pd or Pd-Ni nanoparticles that are supported Vulcan carbon and study their electrochemical response in RDE. Their behavior is compared to non-carbon-coated Pd or Pd-Ni. The two kinds of catalysts materials are also thoroughly evaluated in environmental transmission electron microscopy (E-TEM) mode, using various temperature, either in high vacuum, oxygen, or hydrogen gas; these conditions were applied to mimic the inert or oxidizing/reducing environments witnessed in operating fuel cells and observe the behavior of the nanoparticles in such conditions. The experiments were conducted using a FEI TITAN E-TEM at IRCELYON, and the fast camera in the system provided the video of described experiments. It is shown that the carbon-coated Pd or Pd-Ni nanoparticles have enhanced robustness than their non-coated counterparts.

Carbon nanotube-bridged N-doped mesoporous carbon nanosphere with atomic and nanoscaled M (M = Fe, Co) species for synergistically enhanced oxygen reduction reaction

Rational design of hierarchically structured carbon nanomaterials and also the facile regulation of their metal species decoration for enhanced oxygen reduction reaction (ORR) are urgently required. Herein, N-doped carbon nanospheres (N-MCN) with plentiful pyridinic and graphitized N-induced active sites were closely bridged with carbon nanotubes to remedy the conductivity loss of N-doping. The as-obtained [email protected] exhibited hierarchically porous structure with large surfaces area and good conductivity with small charge transfer resistance, which therefore had a superior ORR activity to the other carbon-base catalysts. Importantly, the metal species (M = Fe or Co) can be loaded in this porous [email protected] via a simple co-pyrolysis, where their numbers and shapes can be easily regulated. It was found the optimal adsorption of metal ions into the precursors produced both single atom and few carbon-coated nanoparticles in M/[email protected], which thus synergistically contributed the enhanced ORR performances, including large current density, low onset and half-wave potentials, as well as superior stability and methanol tolerance than those of commercial 20 wt% Pt/C. Moreover, M/[email protected] also demonstrated comparable oxygen evolution reaction activity to RuO2 possibly due to the regulated metal species. This work provided a strategy to regulate the nanostructure and intrinsic active sites of carbon-based electrocatalysts.

Electrochemical Properties of Sn/C Nanoparticles Fabricated by Pulse Wire Evaporation for Lithium Secondary Batteries.

In this work, bare Sn and carbon-coated Sn nanoparticles were prepared by a pulsed wire evaporation process. The effect of binder and pressing ratio on electrochemical properties of Sn/C composite electrodes was investigated to enhance the structural stability of Sn anode. The electrode containing the polyamide-imide (PAI) binder with high tensile strength (52 MPa) exhibited higher coulombic efficiency and better cycle performance compared to the electrode with the conventional polyvinylidene fluoride (PVdF) binder. The 5%-pressed Sn/C electrode with the proper porosity in the electrode demonstrated the best cycle performance corresponding to 45% of capacity retention ratio until 100 cycles.

Stretchable Electrochemical Biosensing Platform Based on Ni-MOF Composite/Au Nanoparticle-Coated Carbon Nanotubes for Real-Time Monitoring of Dopamine Released from Living Cells

Existing electrochemical biosensing platforms, using traditional rigid and unstretchable electrodes, cannot monitor the biological signaling molecules released by cells in a mechanically deformed state in real time. Here, a stretchable and flexible electrochemical sensor was developed based on nickel metal-organic framework composite/Au nanoparticle-coated carbon nanotubes (Ni-MOF composite/AuNPs/CNTs) for sensitive detection of dopamine (DA) released by C6 living cells in real time. A Ni-MOF composite was obtained by introducing Ni, NiO, and a carbon frame onto the surface of two-dimensional (2D) Ni-MOF nanosheets using an efficient one-step calcination method. The hybrid of Ni-MOF composite/AuNPs/CNTs that deposited on the poly(dimethylsiloxane) (PDMS) film endowed the sensor with excellent electrochemical performance with a wide linear range of 50 nM to 15 μM and a high sensitivity of 1250 mA/(cm2 M) and also provided the sensor with desirable stability against mechanical deformation. Furthermore, the stretchable electrode also displayed good cellular compatibility while C6 living cells can be cultured and proliferated on it with strong adhesion. Then, the DA released by C6 living cells with chemical induction in both natural and stretched states was monitored using our stretchable and flexible electrochemical sensor in real time. This indicates that our new design of flexible Ni-MOF composite/AuNPs/CNTs/PDMS (NACP) film electrodes provides more opportunities for the detection of chemical signals released from cells and soft living organisms even under mechanically deformed states.

Enhanced electrochemical energy storage properties of carbon coated Co3O4 nanoparticles-reduced graphene oxide ternary nano-hybrids

In this article, we have synthesized carbon-coated cobalt oxide nanoparticles (NPs) and their nanocomposite with reduced graphene oxide (C@Co3O4/r-GO) via chemical and ultrasonication techniques. The observed higher electrical conductivity (1.4 × 10−3 S/m) of the nanocomposite than the pristine NPs (1.9 × 10−8 S/m) was due to the combined effect of the carbon-coating and r-GO nanosheets. The higher specific surface area (118 m2/g) of the nanocomposite was due to the relived agglomeration of the NPs via the carbon-coating and r-GO matrix. The nanocomposite based electrode shows exceptional gravimetric capacitance of 674 F/g at 1 A/g and loses just 18% of its initial capacitance after 103 charges/discharge cycles. The superior electrochemical performance of the nanocomposite was due to its higher surface area and synergistic improvements between carbon-coated NPs and highly conductive r-GO nanosheets. In the nanocomposite, the r-GO nanosheets play a double role to increase the energy storage properties. For example, the r-GO sheets acted as a capacitive supplement as well as a conductive matrix for a speedy redox reaction. Highly conductive nanocomposite also showed lower charge transfer resistance (Rct ~ 12.78 Ω) during the electrochemical impedance spectroscopic (EIS) tests that further facilitated the redox reaction to achieve higher pseudocapacitance. The observed electrical and electrochemical results demonstrate the potential of the C@Co3O4/r-GO nanocomposite for hybrid supercapacitors.

Field emission characteristics of metal nanoparticle-coated carbon nanowalls

Metal nanoparticles are deposited on nitrogen-incorporated carbon nanowalls (CNWs) using Ag, Au, In, and Mg as metal species for enhancing field emission. Morphology, coverage, chemical composition, and crystallinity of the metal coatings on CNW surfaces are examined by varying nominal thickness of metals within 10 nm. The emission characteristics reveal that coating CNWs with any metal species lowers emission turn-on fields and thus increases emission efficiency. The inverse dependence of field enhancement factor and turn-on field upon nominal thickness of metals confirms that additional field amplification at metal nanoparticles governs emission efficiency regardless of work functions of the metals. The Ag-coated CNWs retain the highest current density for long-time emission at a constant applied field, while the non-coated CNWs have higher emission stability and a larger time constant of current degradation than the metal-coated ones.

Synthesis of monodisperse rod-shaped silica particles through biotemplating of surface-functionalized bacteria.

Mesoporous silica particles of controlled size and shape are potentially beneficial for many applications, but their usage may be limited by the complex procedure of fabrication. Biotemplating provides a facile approach to synthesize materials with desired shapes. Herein, a bioinspired design principle is adopted through displaying silaffin-derived 5R5 proteins on the surface of Escherichia coli by genetic manipulations. The genetically modified Escherichia coli provides a three-dimensional template to regulate the synthesis of rod-shaped silica. The silicification is initiated on the cell surface under the functionality of 5R5 proteins and subsequentially the inner space is gradually filled. Density functional theory simulation reveals the interfacial interactions between silica precursors and R5 peptides at the atomic scale. There is a large conformation change of this protein during biosilicification. Electrostatic interactions contribute to the high affinity between positively charged residues (Lys4, Arg16, Arg17) and negatively charged tetraethyl orthosilicate. Hydrogen bonds develop between Arg16 (OH), Arg17 (OH and NH), Leu19 (OH) residues and the forming silica agglomerates. In addition, the resulting rod-shaped silica copy of the bacteria can transform into mesoporous SiOx nanorods composed of carbon-coated nanoparticles after carbonization, which is shown to allow superior lithium storage performance.

Zn-substituted iron oxide nanoparticles from thermal decomposition and their thermally treated derivatives for magnetic solid-phase extraction

Controlled thermal decomposition of zinc and iron acetylacetonates in the presence of oleic acid and oleylamine provided surfactant-capped magnetic nanoparticles with narrow size distribution and the mean diameter of ≈15 nm. The combined study by XRD, XRF and Mössbauer spectroscopy revealed three important features of the as-prepared nanoparticles. First, the actual ratio of Zn:Fe was considerably lower in the product compared to the initial ratio of metal precursors (0.14 vs. 0.50). Second, a pure stoichiometric Zn-doped magnetite system, specifically of the composition Zn0.37Fe2.63O4, with no signatures of oxidation to maghemite was formed. Third, Zn2+ ions were distributed at both tetrahedral and octahedral sites, and the observed preference for the tetrahedral site was only twice as high as for theoctahedral site. Furthermore, carbon-coated nanoparticles were achieved by pyrolysis of the surfactants at 500 °C, providing a potential sorbent of organic pollutants with room-temperature magnetization as high as 79.1 emu g−1 and very low carbon content of 5 wt%. The thermal treatment, albeit intended only for the carbonization of surfactants, did alter also the non-equilibrium cation distribution toward the equilibrium one by the relocation of a considerable fraction of the octahedrally coordinated Zn2+ to the tetrahedral sites. Preliminary experiments with magnetic solid-phase extraction of β-estradiol from aqueous solutions evidenced applicability and reusability of the carbon-coated product in the separation of steroid pollutants.

Self-Assembled Nanoparticle Supertubes as Robust Platform for Revealing Long-Term, Multiscale Lithiation Evolution

Summary Herein, free-standing supertubes, composed of a single layer of close-packed carbon-coated nanoparticles, are fabricated by a confined-epitaxial-assembly strategy. Benefiting from the tubular geometry, monolayer superlattice structure, and uniform and conformal carbon coating, such free-standing supertubes promise high electrochemical performance while simultaneously serving as a robust platform for reliably elucidating the structure-performance relationship of lithium-ion batteries (LIBs). As a model, Fe3O4 supertubes, when used as LIB anodes, can deliver a capacity of ∼800 mAh g−1 after 500 cycles at 5 A g−1, outperforming most Fe3O4-based materials reported previously. More importantly, the structural evolution of Fe3O4 supertubes is revealed at meso-/nano-/atomic scales simultaneously upon lithiation and delithiation, which correlates well with the battery's capacity reactivation, stabilization, and degradation behaviors during the course of 500 cycles.

An advanced blackberry-shaped Na3V2(PO4)3 cathode: Assists in high-rate performance and long-life stability

Na3V2(PO4)3 is suitable for the rapid migration of Na+ in the electrochemical reaction process due to its open-ended structure of 3D sodium super ionic conductor type, but the low electronic conductivity and large volume deformation during the repeated Na+ extraction/insertion severely limit its rate and cycle performance. Herein, a blackberry-shaped Na3V2(PO4)3 is synthesized for the first time to address both of the problems, and the structure is composed of aggregated carbon-coated nanoparticles attaching to highly conductive 3D porous carbon scaffolds, hence provides efficient pathways for both electrons and ions. For sodium-ion batteries, the blackberry-shaped Na3V2(PO4)3 exhibits high reversible capacity (116 mA h g−1 at 0.2 C), high-rate performance (83 mA h g−1 at 20 C) and long-life stability (94.4% capacity retention after 4500 cycles at 10 C). The excellent electrochemical performance indicates that blackberry-shaped Na3V2(PO4)3 has better application prospects as an advanced cathode material for sodium-ion batteries.

Flexible Array of Microsupercapacitor for Additive Energy Storage Performance Over a Large Area.

An on-chip microsupercapacitor (MSC) pattern is obtained by layer-by-layer spray deposition of both manganese dioxide (MnO2) nanoparticle-coated carbon nanotubes (MnO2-CNTs) and MnO2 nanosheet-decorated reduced graphene oxide (MnO2-rGO) on mechanically robust, flexible polyethylene terephthalate. Layer-by-layer patterning of MSC electrodes offers rapid in-plane diffusion of electrolyte ions in electrodes the layered electrode and hence ultrahigh capacitance and energy density of 7.43 mF/cm2 (32300 mF/cm3) and 0.66 μW h/cm2 (2870 μW h/cm3), respectively, are obtained. A robust electrochemical response was measured under multiple bending of the solid-state flexible MSC as well as under repetitive cycles (∼5000).

One-Step Self-Assembly Synthesis α-Fe2O3 with Carbon-Coated Nanoparticles for Stabilized and Enhanced Supercapacitors Electrode

A cocoon-like α-Fe2O3 nanocomposite with a novel carbon-coated structure was synthesized via a simple one-step hydrothermal self-assembly method and employed as supercapacitor electrode material. It was observed from electrochemical measurements that the obtained α-Fe2O3@C electrode showed a good specific capacitance (406.9 Fg−1 at 0.5 Ag−1) and excellent cycling stability, with 90.7% specific capacitance retained after 2000 cycles at high current density of 10 Ag−1. These impressive results, presented here, demonstrated that α-Fe2O3@C could be a promising alternative material for application in high energy density storage.

Development and characterization of PLA-mPEG copolymer containing iron nanoparticle-coated carbon nanotubes for controlled delivery of Docetaxel

The practicability of application of single wall carbon nanotubes doped with iron oxide nanoparticles (Fe3O4-iSWNTs) and coated with Poly (lactic acid)-co-methoxy polyethylene glycol copolymeric (PLA-co-mPEG) micelles as a smart drug delivery systems based on hybrid nanomaterials (HNDDSs) for the puissant chemotherapy agent Docetaxel (DTX) were studied. The SWNTs treatment in the acidic medium leads to formation of carboxylate groups on the surface of SWNTs and functionalization by iron oxide nanoparticles, Then PLA-co-mPEG was synthesized by ring-opening polymerization and prepared in the form of micelles and coated the Fe3O4-iSWNTs.The surface functionalization of nanomaterials and the type of surface-interaction were characterized by Fourier transform spectroscopy (FT-IR), proton nuclear magnetic resonance (H-NMR), X-ray powder diffraction (XRD), vibrating sample magnetometers (VSM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), field-emission gun scanning electron microscope and energy dispersive X-ray (FE-SEM-EDX). The particle size of nanocomposites examined by FE-SEM was in the range of 15–50 nm. The in-vitro drug release and cytotoxicity investigations of DTX loaded on Fe3O4-iSWNTs/PLA-co-mPEG nanocomposites were also studied. Docetaxel release in tumor environment simulated conditions showed sustained release manner (43.7% was released during 348.5 h) And kinetic mechanism of release according to log-probability equation. The designed nanocomposite showed no apparent evidence of toxicity to MCF7 cancer cells while DTX-loaded nanocomposites indicated enhanced antitumor activity in comparison to free DTX, 59% and 36% of the cells were viable after incubation, respectively. It was concluded that these findings may open the possibilities for targeted and sustained delivery of DTX to the cancerous tissues under external magnetic fields.

Iron Oxyhydroxide Nanoparticle-Coated Carbon Cloth Electrode for Remediation of Cr(VI)-Contaminated Wastewater.

Among in situ and ex situ groundwater technologies, electrochemical treatment has been successfully employed to remediate water heavily contaminated with metals. Electrochemical treatment of Cr(VI)-contaminated wastewater has been attempted using various factors such as electrode materials, surfactants, and electrolytes. In this study, inexpensive carbon cloth was selected and coated with iron oxyhydroxide nanoparticles to enhance electrochemical remediation of Cr(VI)-contaminated wastewater. Iron oxyhydroxide nanoparticles (INP) synthesized by chemical precipitation were coated on carbon cloth electrodes by immersion to examine Cr(VI) removal. The efficiency of Cr(VI) reduction/immobilization was compared between carbon cloth (CC) and carbon cloth coated with iron oxyhydroxide nanoparticles (INP-CC) with/without DC application at a constant potential of 5.0 V to treat water contaminated with 100 mg/L Cr(VI) for 48 h. The removal rate of Cr(VI) was as follows: 10% for CC electrodes and 32% for INP-CC electrodes, compared to >90% for both CC and INP-CC electrodes with DC application for 48 h. In the INP-CC + EC group the pH-Eh condition tended to acidic oxidizing condition due to oxidative substances, O2(g) and hydrogen ions generated on anodic reaction during 12~24 h when Cr(VI) removal reached at 80%, but the CC + EC group remained with minor change for 36 h resulting less reduction efficiency of Cr(VI), despite a successful removal efficiency after 48 h which is similar to the INP-CC + EC group. These results indicated that multiple interactions (C/Cr6+–Cr3+/Fe3+–Fe2+/H+–OH−) on the surface of CC and INP-CC enhanced by EC might contribute to reduction of Cr(VI) and adsorption/precipitation of chromate ions. In particular, INP-CC+ EC might perform dual roles as an electron donor for Fe2+ and/or as an absorbent with DC application in Cr(VI) immobilization. INP-CC enhanced-EC technology could be an economic and efficient approach to remediation of wastewater heavily contaminated with Cr(VI).

Flexible polyaniline/carbon nanotube nanocomposite film-based electronic gas sensors

Real-time ammonia (NH3) detection in anaerobic digestion is highly desirable, due to the ammonia inhibition on methane production. Here, the interconnected nanocomposite network of polyaniline (PANI) nanoparticle-coated carbon nanotube (CNT) and PANI nanofiber is fabricated by adding ammonium persulfate into CNT-containing aniline solution for PANI polymerization and film deposition. The film is assembled as high-sensitive ammonia sensors, exhibiting highly sensitive NH3 sensing from 200ppb to 50ppm, fast response/recovery time, room-temperature operation without external aid, reliable flexibility and excellent selectivity to NH3 compared to other volatile organic compounds.

Synthesis of the Carbon-Coated Nanoparticle Co9S8 and Its Electrochemical Performance as an Anode Material for Sodium-Ion Batteries.

A Co9S8/C nanocomposite is prepared using a solid-state reaction followed by a facile mechanical ball-milling treatment, with sucrose as the carbon source. The phases, morphologies, and detailed structures of the Co9S8/C nanocomposite are well-characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. When evaluated as an anode material for sodium-ion batteries, the Co9S8/C nanocomposite electrode displays a reversible capacity of ∼567 mA h g-1 in the initial cycle and maintains a reversible capacity of ∼320 mA h g-1 after 30 cycles, indicating a larger capacity and a stable cycling performance. For comparison, the electrochemical performances of Co9S8 and Co9S8/C samples synthesized using the solid-state reaction are also displayed. The ex situ XRD and transmission electron microscopy tests demonstrate that Co9S8 undergoes a conversion-type sodium storage mechanism.

On polystyrene–block polyisoprene–block polystyrene filled with carbon-coated Ni nanoparticles

The manuscript focuses on the dispersion of magnetic nanoparticles within self-assembling block copolymers, on the preferential localization of nanoparticles and on the effect of their concentration on the magnetic properties of the nanocomposites and on the self-assembly features of the matrix. Carbon-coated nickel nanoparticles dispersed within polystyrene–block polyisoprene–block polystyrene have been investigated by Raman, X-ray, SQUID, differential scanning calorimetry, and electron microscopy. The effect of nanofiller on the self-assembly features of the block copolymer is reported. Preferential localization of nanofiller within the soft phase was noticed below 20 wt% nanofiller. Higher loadings with nanoparticles showed an uniform distribution of nanofiller within the block copolymer, consistent with the destruction of self-assembly. The effect of nanoparticles’ concentration on blocking temperature is discussed.