Carbon Nanodomains Research Articles

Incorporation of edge-N into La-doped hierarchical carbon framework enables high-efficiency phosphate electrosorption: Boosting accessible active centers and bridging charge transfer paths

Achieving high-efficiency removal of phosphate has been an urgent issue to combat eutrophication and meet ever-stricter emission standards. Electro-assisted adsorption, a mild electrochemical technology, demonstrated great potential for wastewater treatment owing to the merits of considerable removal performance, facile operation, and energy efficiency. Exploring and boosting the properties of electrode materials is exceedingly vital for technological advancement. In this study, the novel edge-N decorated La-doped hierarchical carbon composites (LNPCs) were developed via in-situ nucleation and one-pot pyrolysis strategy as phosphate capture electrodes. The LNPC900 electrode exhibited an ultrahigh phosphate removal capability of 533.06 mg PO43- g−1 at 1.2 V, surpassing most of the reported electrode materials. Furthermore, this electrochemical system also performed well in the purification of natural river water with low phosphate concentration, where the treated concentration was below the first-class emission standard in China (0.5 mg P L−1). Comprehensive analysis and theoretical calculations indicate that the synergistic property of edge-N and small graphitic carbon nanodomains ensured more accessible active centers and conductive efficiency. The superb phosphate removal capability mainly originated from the coupling contribution of the electrical double layer capacitance, ligand exchange, and electrostatic attraction. This study possesses insight into the theoretical basis for the practical application of phosphate electrosorption and provides a new level of the technology.

Durable Li2CN2 Solid Electrolyte Interphase Wired by Carbon Nanodomains via In Situ Interface Lithiation to Enable Long‐Cycling Li Metal Batteries

AbstractLithium metal batteries (LMBs) are becoming the promising candidate of high‐energy storage systems. However, the fragile natural solid electrolyte interphase (SEI) cannot retard the Li dendrite growth at anode, which will cause the low coulombic efficiency (CE) of Li plating/stripping and safety hazards in LMBs. Here, an in situ construction strategy of novel artificial SEI consisting of Li2CN2 ionic conductor wired by carbon nanodomains via dicyandiamide solution reaction method on Li metal surface is proposed. This lithiophilic Li2CN2 has the higher anti‐reduction stability and longer critical length for Li dendrite, showing the excellent dendrite suppressing ability. The wired carbon domains promote the electron connection and charge homogenization in SEI, leading to the uniform Li nucleation around Li2CN2/C grains with enhanced interface kinetics and reduced polarization. This dual conductive Li2CN2/C network enables the durable preservation of high CE and low voltage hysteresis during Li plating/stripping, endowing LiNi0.8Mn0.1Co0.1O2/Li cells with ultralong cycling life exceeding 1000 cycles at high rate. The cycling stabilization effect is also remarkable even under thin Li anode and high‐loading cathode conditions. This study provides a solution to robust SEI configuration of high conductivity via in situ interface lithiation reaction for high‐performance LMBs.

A Reverse‐Defect‐Engineering Strategy toward High Edge‐Nitrogen‐Doped Nanotube‐Like Carbon for High‐Capacity and Stable Sodium Ion Capture

AbstractDeveloping high‐performance defect‐rich carbon materials with abundant accessible active sites is exceedingly vital for electrochemical water desalination, but this still remains a significant challenge. Herein, a reverse‐defect‐engineering strategy is reported to synthesize high edge‐nitrogen‐doped nanotube‐like carbon through the annealing process of protonated g‐C3N4 under H2 atmosphere. The hydrogen bonds interaction between the proton and nitrogen atoms performs a crucial role in regulating nitrogen configurations. The nitrogen‐doped carbon obtained from HCl pretreatment (HCl‐NC) reduces the proportion of graphitic N and exhibits a high ratio of pyrrolic N to pyridinic N. Thus, the resulting synergetic structure of high edge‐type N and small graphitic carbon nanodomains ensures more accessible active sites and fast charge‐transfer kinetics simultaneously, contributing to high desalination capacity (100.3 mg g−1 at 1.2 V), fast time‐average specific adsorption rate (1.7 mg g−1 min−1), low energy consumption (82.9 kJ molNaCl−1), and superior cyclic stability (no signs of performance decay after long‐term cycling). The Na+‐intercalation mechanism and structure‐response relationship of HCl‐NC are revealed by the electrochemical quartz crystal microbalance with dissipation monitoring and density functional theory calculations, respectively. This study provides a novel idea to modulate the nanotube‐like, nitrogen‐containing configurations for engineering carbon nanomaterials for advanced electrochemical applications.

3D Periodic and Interpenetrating Tungsten-Silicon Oxycarbide Nanocomposites Designed for Mechanical Robustness.

Metal-ceramic nanocomposites exhibit exceptional mechanical properties with a combination of high strength, toughness, and hardness that are not achievable in monolithic metals or ceramics, which make them valuable for applications in fields such as the aerospace and automotive industries. In this study, interpenetrating nanocomposites of three-dimensionally ordered macroporous (3DOM) tungsten-silicon oxycarbide (W-SiOC) were prepared, and their mechanical properties were investigated. In these nanocomposites, the crystalline tungsten and amorphous silicon oxycarbide phases both form continuous and interpenetrating networks, with some discrete free carbon nanodomains. The W-SiOC material inherits the periodic structure from its 3DOM W matrix, and this periodic structure can be maintained up to 1000 °C. In situ SEM micropillar compression tests demonstrated that the 3DOM W-SiOC material could sustain a maximum average stress of 1.1 GPa, a factor of 22 greater than that of the 3DOM W matrix, resulting in a specific strength of 640 MPa/(Mg/m3) at 30 °C. Deformation behavior of the developed 3DOM nanocomposite in a wide temperature range (30-575 °C) was investigated. The deformation mode of 3DOM W-SiOC exhibited a transition from fracture-dominated deformation at low temperatures to plastic deformation above 425 °C.

Shedding light onto the nano- and micro-structures of B-containing SiOC glasses using high resolution TEM 3D imaging

The internal structure of nanostructured pyrolyzed SiBOC glasses has been analyzed using a combination of transmission electron microscopy techniques including high resolution imaging, EELS spectroscopy and 3D imaging. For the first time, we provide direct information on the 3D architecture within such complex glasses containing SiC nanograins, silica-rich and carbon nanodomains. Their sizes and relative 3D distribution have been precisely quantified. It was shown that the SiC nanocrystals and the silica-rich domains exhibit different types of connectivities with the graphitic carbon network. A direct evidence of the existence of “covalent” bridges between the edges of graphitic nanoplatelets and the SiC nanocrystals is provided. In addition, it was demonstrated that the silica rich domains are not covalently bonded to the graphitic platelets. As a consequence, this amorphous phase can be dissolved into HF and may generate a bimodal porosity, in strong relationship with the initial nanostructure of the SiBOC glass specimen.

A Highly Efficient Oxygen Evolution Catalyst Consisting of Interconnected Nickel-Iron-Layered Double Hydroxide and Carbon Nanodomains.

In this work, a one-pot solution method for direct synthesis of interconnected ultrafine amorphous NiFe-layered double hydroxide (NiFe-LDH) (<5 nm) and nanocarbon using the molecular precursor of metal and carbon sources is presented for the first time. During the solvothermal synthesis of NiFe-LDH, the organic ligand decomposes and transforms to amorphous carbon with graphitic nanodomains by catalytic effect of Fe. The confined growth of both NiFe-LDH and carbon in one single sheet results in fully integrated amorphous NiFe-LDH/C nanohybrid, allowing the harness of the high intrinsic activity of NiFe-LDH due to (i) amorphous and distorted LDH structure, (ii) enhanced active surface area, and (iii) strong coupling between the active phase and carbon. As such, the resultant NiFe-LDH/C exhibits superior activity and stability. Different from postdeposition or electrostatic self-assembly process for the formation of LDH/C composite, this method offers one new opportunity to fabricate high-performance oxygen evolution reaction and possibly other catalysts.

Controlled Solvent-Free Formation of Embedded PDMS-Derived Carbon Nanodomains with Tunable Fluorescence Using Selective Laser Ablation with A Low-Power CD Laser.

We present a study of the application of a single-step and solvent-free laser-based strategy to control the formation of polymer-derived fluorescent carbon nanodomains embedded in poly-dimethylsiloxane (PDMS) microchannels. A low-power, laser-induced microplasma was used to produce a localised combustion of a PDMS surface and confine nanocarbon byproducts within the exposed microregions. Patterns with on-demand geometries were achieved under dry environmental conditions thanks to a low-cost 3-axis CD-DVD platform motorised in a selective laser ablation fashion. The high temperature required for combustion of PDMS was achieved locally by strongly focusing the laser spot on the desired areas, and the need for high-power laser was bypassed by coating the surface with an absorbing carbon additive layer, hence making the etching of a transparent material possible. The simple and repeatable fabrication process and the spectroscopic characterisation of resulting fluorescent microregions are reported. In situ Raman and fluorescence spectroscopy were used to identify the nature of the nanoclusters left inside the modified areas and their fluorescence spectra as a function of excitation wavelength. Interestingly, the carbon nanodomains left inside the etched micropatterns showed a strong dependency on the additive materials and laser energy that were used to achieve the incandescence and etch microchannels on the surface of the polymer. This dependence on the lasing conditions indicates that our cost-effective laser ablation technique may be used to tune the nature of the polymer-derived nanocarbons, useful for photonics applications in transparent silicones in a rapid-prototyping fashion.

Mechanical and microwave absorbing properties of Tyranno ® ZMI fiber annealed at elevated temperatures

Abstract The tensile strength and microwave absorbing properties of the amorphous silicon carbide fiber (Tyranno-ZMI) annealed at different temperatures were studied. The tensile strength of the as-received ZMI fiber tows was 1.1 GPa; and the average real and imaginary parts of permittivities of the as-received ZMI/resin samples were 11.3 and 10.5 respectively. The major dielectric loss mechanism of the fibers was conduction loss, which was due to high electrical conductivity of the enriched carbon in ZMI fibers. The 2.0 mm thick ZMI/resin composites could absorb 80% microwave energy in X band, indicating good microwave absorbing property. After heat treatment, fibers degraded gradually and permittivities increased, which were mainly attributed to the decomposition of amorphous SiC x O y and the growth of the SiC nanocrystals and free carbon nanodomains.

Influence of sp(3)-sp(2) Carbon Nanodomains on Metal/Support Interaction, Catalyst Durability, and Catalytic Activity for the Oxygen Reduction Reaction.

In this work, platinum nanoparticles were impregnated by two different techniques, namely the carbonyl chemical route and photodeposition, onto systematically surface-modified multiwalled carbon nanotubes. The different interactions between platinum nanoparticles with sp(2)-sp(3) carbon nanodomains were investigated. The oxidation of an adsorbed monolayer of carbon monoxide, used to probe electronic catalytic modification, suggests a selective nucleation of platinum nanoparticles onto sp(2) carbon nanodomains when photodeposition synthesis is carried out. XPS attests the catalytic center electronic modification obtained by photodeposition. DFT calculations were used to determine the interaction energy of a Pt cluster with sp(2) and sp(3) carbon surfaces as well as with oxidized ones. The interaction energy and electronic structure of the platinum cluster presents dramatic changes as a function of the support surface chemistry, which also modifies its catalytic properties evaluated by the interaction with CO. The interaction energy was calculated to be 8-fold higher on sp(3) and oxidized surfaces in comparison to sp(2) domains. Accelerated Stability Test (AST) was applied only on the electronic-modified materials to evaluate the active phase degradation and their activity toward oxygen reduction reaction (ORR). The stability of photodeposited materials is correlated with the surface chemical nature of supports indicating that platinum nanoparticles supported onto multiwalled carbon nanotubes with the highest sp(2) character show the higher stability and activity toward ORR.

Porous carbons from ionic liquid precursors confined within nanoporous silicas

We propose Vycor® porous glass and various types of enhanced pore size Vycor® (hereafter referred to eps-Vycor®) as hard templates for the development of micro-mesoporous N-doped carbons via nanocasting/thermolytic treatment of 1-alkyl-3-methylimidazolium tricyanomethanide Ionic Liquids (ILs). Vycor® is less costly than mesoporous ordered silicas of the type SBA-15 and MCM-41 which are sometimes employed for the development of micro-mesoporous carbons (CMK-3) as inverse replicas from the solid matrix; in addition Vycor® and eps-Vycor® can also be used in the form of sheets or tubes, thus opening the road for the development of composite carbon/silica substrate membranes with molecular sieving characteristics. We find that the nitrile functional groups in the anion of the IL lead to enhanced carbon yield while nanocasting and nanoconfinement are decisive for producing functional carbons with high levels of microporosity. In addition, the developed functional carbons exhibited extended mesoporosity with characteristic H2 or H1 types of hysteresis in their N2 adsorption isotherms (77 K), solely in the cases when eps-Vycor® was applied as the hard template. The widening of the Vycor® pores, especially of the pore constrictions by treatment in HF for varying periods led to the formation of thicker carbon nanodomains that exhibited the required mechanical stability to retain the inverse structure (replica) upon dissolution of the hard template.

Mesoporous silicon oxycarbide materials for controlled drug delivery systems

The suitability of using mesoporous silicon oxycarbide materials as controlled drug delivery systems is reported here. The silicon oxycarbide materials are known for their nanostructured nature composed of silica and carbon nanodomains in an amorphous matrix. The SiOC present a large surface area and a bimodal porous structure with pores of 6 and 100nm size. The surface modification of the SiOC with amino-containing silanes leads to a similar porous structure with the grafted silane adopting a specific configuration depending on the amount of silane. The availability of the amino groups to interact with the loaded drug molecule has been determined through infrared spectroscopy whereas the amount of drug adsorbed on the material has been calculated through UV–vis spectroscopy and thermogravimetry. The materials are biologically inactive but they can host a large amount of active drug molecules per cm2 into their porous structure. The adsorption kinetics have been compared with mesoporous silica and mesoporous active carbon and we have deducted that the drug penetrates faster in the SiOC than in the AC and the adsorption mechanism occurs via acceptor–donor interactions between the drug molecules and the surface of the materials.

Low-cost formation of bulk and localized polymer-derived carbon nanodomains from polydimethylsiloxane.

We present two simple alternative methods to form polymer-derived carbon nanodomains in a controlled fashion and at low cost, using custom-made chemical vapour deposition and selective laser ablation with a commercial CD-DVD platform. Both processes presented shiny and dark residual materials after the polymer combustion and according to micro-Raman spectroscopy of the domains, graphitic nanocrystals and carbon nanotubes have successfully been produced by the combustion of polydimethylsiloxane layers. The fabrication processes and characterization of the byproduct materials are reported. We demonstrate that CVD led to bulk production of graphitic nanocrystals and single-walled carbon nanotubes while direct laser ablation may be employed for the formation of localized fluorescent nanodots. In the latter case, graphitic nanodomains and multi-wall carbon nanotubes are left inside microchannels and preliminary results seem to indicate that laser ablation could offer a tuning control of the nature and optical properties of the nanodomains that are left inside micropatterns with on-demand geometries. These low-cost methods look particularly promising for the formation of carbon nanoresidues with controlled properties and in applications where high integration is desired.

Structure properties relationship in silicon oxycarbide glasses obtained by spark plasma sintering

Spark plasma sintering (SPS) technology has been employed to obtain nanocomposites of a silicon oxycarbide glass matrix (SiOC) reinforced with SiC, SiO2 or Al2O3 nanoparticles. The characterization of the obtained materials revealed a dependence on the structural characteristics of the precursors with the properties and the reactions taking place during sintering. In the materials reinforced with SiO2, the stoichiometry of the oxycarbide phase is independent on the carbon content in the SiOC whereas when reinforcing with Al2O3, the mullite phase formation occurs at expense of the SiOC metastable phase. The measured mechanical and electrical properties have been revealed to be dependent of the size of the carbon nanodomains.

Dielectric and microwave absorption properties of polymer derived SiCN ceramics annealed in N2 atmosphere

Abstract Porous SiCN ceramics were successfully fabricated by pyrolysis of a kind of polysilazane. The effects of annealing temperature on the microstructure evolution, direct-current electrical conductivity, dielectric properties, and microwave absorption properties of SiCN in the frequency range 8.2–12.4 GHz (X-band) were investigated. With the increase of annealing temperature, SiC, Si3N4 and free carbon nanodomains are gradually formed in the SiCN. Both the SiC and free carbon nanodomains lead to the increases of the complex relative permittivity and loss tangent of SiCN. With the increase of the annealing temperature, the average real permittivity, imaginary permittivity and loss tangent increase from 4.4, 0.2 and 0.05 to 13.8, 6.3 and 0.46, respectively. The minimum reflection coefficient and the frequency bandwidth below −10 dB for SiCN annealed at 1500 °C are −53 dB and 3.02 GHz, indicating good microwave absorption properties.

Micron-Sized Single-Crystal-like CoAPO-5/Carbon Composites Leading to Hierarchical CoAPO-5 with Both Inter- and Intracrystalline Mesoporosity

Commercial mesopores-containing carbon (carbon black BP2000) has been used as crystallization host as well as hard template of intracrystalline mesopores in CoAPO-5 materials prepared with N-methyldicyclohexylamine as specific structure-directing agent. As a result, micrometer-sized AFI-structured terminated-tip (pencil-like) hexagonal prims have been obtained. Despite the appearance of single crystals, the crystals are actually composites formed by a large number of elongated-shape CoAPO-5 and carbon nanodomains. Indeed, the removal of carbon by calcination leaves an inorganic Co-doped AlPO4-based material having a complex hierarchical pore system, formed by the expected microporosity for an AFI-structured material and both intra- and intercrystalline mesoporosity. In good agreement with the nanocomposite nature of these micrometer-sized crystals, the size of their fibers generated by burning the carbon matrix can be relatively controlled by the conditions of the calcination processes. Under optimized synthesis and calcination conditions, AFI-structured materials with high mesoporous surface area and pore volume can be afforded.

Electrical, dielectric and microwave-absorption properties of polymer derived SiC ceramics in X band

Porous silicon carbide ceramics were successfully fabricated by pyrolysis of a polycarbosilane precursor. The direct-current electrical conductivity, dielectric and microwave absorption properties over the frequency range of 8.2–12.4GHz (X band) were investigated. Polymer derived silicon carbide is composed of SiC nano-crystals and free carbon nanodomains. The high-temperature direct-current conductivities of samples indicate the transformation of amorphous semiconductor into polycrystalline semiconductor with the increase of the annealing temperature. After annealed at 1500°C, the real permittivity, imaginary permittivity and the loss tangent increase from 3.6, 0.17 and 0.05 to 8.49, 10.01 and 1.18, respectively. The increases of the relative complex permittivity and loss tangent are ascribed to the appearance of SiC nano-crystals and free carbon nanodomains. The average reflectivity of the polymer derived SiC ceramics annealed at 1400°C is −9.9dB, which exhibits a promising prospect as microwave absorbing materials.

Surface and Structural Modification of Nanostructured Mesoporous Silicon Oxycarbide Glasses Obtained from Preceramic Hybrids Aged in NH4OH

Highly meso‐porous silicon oxycarbide glasses have been obtained from preceramic hybrid materials aged in NH4OH solutions. Surface characterization reveals the amphoteric character of the surface because of the presence of carbon and silica nanodomains. The dependence of the surface Lewis base constant with the concentration of the NH4OH solution suggests different distribution in the carbon nanodomains because of the addition of the aging solution. Structural characterization reports on the increase in the crosslinking degree in the materials treated in NH4OH, whereas the number of dangling bonds increases significantly in the microporous material taken as a reference.

29Si and13C Solid-State NMR Spectroscopic Study of Nanometer-Scale Structure and Mass Fractal Characteristics of Amorphous Polymer Derived Silicon Oxycarbide Ceramics

Polymer derived silicon oxycarbide ceramics (SiOC-PDCs) with widely different carbon contents have been synthesized, and their structures have been studied at different length scales using high-resolution 13C and 29Si magic-angle-spinning (MAS) NMR spectroscopic techniques. The data suggest that the structure of these PDCs consists of a continuous mass fractal backbone of corner-shared SiCxO4-x tetrahedral units with “voids” occupied by sp2-hybridized graphitic carbon. The oxygen-rich SiCxO4-x units are located at the interior of this backbone with a mass fractal dimension of ∼2.5 while the carbon-rich units display a slightly lower dimensionality and occupy the interface between the backbone and the free carbon nanodomains.

Nanoscale patchworks

Patching carbon and boron nitride nanodomains emerges as an efficient way to engineer bandgaps in graphene, opening a new avenue for optoelectronic devices.

C−BN Patterned Single-Walled Nanotubes Synthesized by Laser Vaporization

We report on the synthesis of C-BN single-walled nanotubes made of BN nanodomains embedded into a graphene layer. The synthesis process consists of vaporizing, by a continuous CO2 laser, a target made of carbon and boron mixed with a Co/Ni catalyst under N2 atmosphere. High-resolution transmission electron microscopy (HRTEM) and nanoelectron energy loss spectroscopy (nanoEELS) provide direct evidence that boron and nitrogen co-segregate with respect to carbon and form nanodomains within the hexagonal lattice of the graphene layer in a sequential manner. A growth model is proposed to account for the observed C-BN self-organization and to explain how kinetics and local energetics at intermediate states can tailor ultimate single layer BN-C heterojunctions.