Synthesis of Graphitic Carbon Coated ZnPS3 and its Superior Electrochemical Properties for Lithium and Sodium Ion Storage

Graphitic carbon-coated ZnPS3 is prepared via direct phosphosulfurization and high energy mechanical milling (HEMM) with multiwall carbon nanotubes (MWCNTs) and first introduced as an anode for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The HEMM process with MWCNTs reduces the particle size of as-synthesized ZnPS3 bulk to 100-500 nm and yields the ≈5 nm thick graphitic carbon coated ZnPS3 nanoparticles, which are the nanocomposites of 5 nm sized nanocrystallites embedded in the amorphous matrix. The ZnPS3 electrode undergoes the combined conversion and alloying reactions with Li and Na ions and exhibits high initial discharge and charge capacities in both LIBs and SIBs. The graphitic carbon-coated ZnPS3 electrode exhibits excellent high-rate capability and long-term cyclability. The superior electrochemical properties can be attributed to high electrical conductivity, high Li ion mobility, and high reversibility and structural stability derived from the graphitic carbon-coated nanoparticles. This study demonstrates that the novel graphitic carbon-coated ZnPS3 is a promising anode material for both LIBs and SIBs and the graphitic carbon coating methodology by HEMM is expected to apply to the various metal oxides, sulfides, and phosphides.

ZIF67-ZIF8@MFC-Derived Co-Zn/NC Interconnected Frameworks Combined with Perfluorosulfonic Acid Polymer as a Highly Efficient and Stable Composite Electrocatalyst for Oxygen Reduction Reactions

The development of precious metal-free (M-N-C) catalysts for the oxygen reduction reaction (ORR) is considered crucial for reducing fuel cell costs. Herein, Co-Zn/NC interconnected frameworks with uniformly dispersed Co nanoparticles and graphitic carbon are designed and successfully synthesized through the in situ growth of zeolitic imidazolate frameworks (ZIF67 and ZIF8) along with biomass nano-microfibrillar cellulose (MFC), followed by pyrolysis. A Co-Zn/NC composite is prepared by combining Co-Zn/NC with a perfluorosulfonic acid polymer. The Co-Zn/NC composite catalyst exhibits excellent ORR catalytic activity (E0 = 0.974 V vs. RHE, E1/2 = 0.858 V vs. RHE) and good long-term durability, with 90% current retention after 10000s, surpassing that of commercial Pt/C in alkaline media. The hierarchical porous structure, coupled with the uniform distribution of Co nanoparticles and nitrogen doping, contributes to superior electrocatalytic performance, while the interconnected frameworks and graphitic carbon ensure good stability. Additionally, the Co-Zn/NC composite demonstrates promising applications in acidic media. This strategy offers significant guidance to develop advanced non-precious metal carbon-based catalysts for highly efficient and stable ORR.

Effect of Methyl Groups on Formation of Ordered or Layered Graphitic Materials from Aromatic Molecules

Developing functionally complex carbon materials from small aromatic molecules requires an understanding of how the chemistry and structure of its constituent molecules evolve and crosslink, to achieve a tailorable set of functional properties. Here, molecular dynamics (MD) simulations are used to isolate the effect of methyl groups on condensation reactions during the oxidative process and evaluate the impact on elastic modulus by considering three monodisperse pyrene-based systems with increasing methyl group fraction. A parameter to quantify the reaction progression is designed by computing the number of new covalent bonds formed. Utilizing the previously developed MD framework, it is found that increasing methylation leads to an almost doubling of bond formation, a larger fraction of the new bonds oriented in the direction of tensile stress, and a higher basal plane alignment of the precursor molecules along the direction of tensile stress, resulting in enhanced tensile modulus. Additionally, via experiments, it is demonstrated that precursors with a higher fraction of methyl groups result in a higher alignment of molecules. Moreover, increased methylation results in the lower spread of single molecule alignment which may lead to smaller variations in tensile modulus and more consistent properties in carbon materials derived from methyl-rich precursors.

Designed NiMoC@C and NiFeMo2C@C core-shell nanoparticles for oxygen evolution in alkaline media

Electrochemical water splitting is one of the most promising and clean ways to produce hydrogen as a fuel. Herein, we present a facile and versatile strategy for synthesizing non-precious transition binary and ternary metal-based catalysts encapsulated in a graphitic carbon shell. NiMoC@C and NiFeMo2C@C were prepared via a simple sol-gel based method for application in the Oxygen Evolution Reaction (OER). The conductive carbon layer surrounding the metals was introduced to improve electron transport throughout the catalyst structure. This multifunctional structure showed synergistic effects, possess a larger number of active sites and enhanced electrochemical durability. Structural analysis indicated that the metallic phases were encapsulated in the graphitic shell. Experimental results demonstrated that the optimal core-shell material NiFeMo2C@C exhibited the best catalytic performance for the OER in 0.5 M KOH, reaching a current density of 10 mA cm-2 at low overpotential of 292 mV for the OER, superior to the benchmark IrO2 nanoparticles. The good performances and stability of these OER electrocatalysts, alongside an easily scalable procedure makes these systems ideal for industrial purposes.

Performance Enhancement of Moisture-driven Power Generators by Photofragmentation of Inorganic Salt Particles

We developed a novel method based on the photofragmentation of inorganic salt particles for improving the moisture-electric energy transformation performance of a moisture-driven power generator (MPG). Infrared laser irradiation on cellulose nanofiber films (CNFs) prepared by a TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation of bleached pulp induced a photothermal conversion of CNFs to porous graphitic carbon films (GCFs) with the catalyst-derived Na₂O₂ particles. Since the laser beam was focused on the top surface of CNF, the gradients of the photothermal conversion of CNFs and Na₂O₂ concentration were created along the thickness direction. Subsequent irradiation with ultraviolet (UV) light induced the photofragmentation of the micrometer-sized Na₂O₂ particles into smaller ones, which increased the surface area of the salt particles in contact with the GCFs and consequently increased the number of effective dissociable charge carriers. When the GCF was exposed to moisture, the dissociated sodium ions migrated along the preformed concentration gradient, producing continuous outputs of current and voltage. At 90% relative humidity, the maximum voltage and current density outputs of the MPG increased from 0.91 V and 18.7 μA/cm² before UV irradiation to 1.10 V and 56.2 μA/cm² after UV irradiation, respectively. Additionally, we demonstrated that a green light-emitting diode could be turned on without capacitors or rectifiers during normal breathing while wearing a face mask with three GCF arrays attached (each 3 mm × 3 mm × 0.1 mm in size).

Promotional Effects on the Catalytic Activity of Co-Fe Alloy Supported on Graphitic Carbon for CO2 Hydrogenation

Starting from the reported activity of Co-Fe nanoparticles wrapped onto graphitic carbon (Co-Fe@C) as CO₂ hydrogenation catalysts, the present article studies the influence of a series of metallic (Pd, Ce, Ca, Ca, and Ce) and non-metallic (S in various percentages and S and alkali metals) elements as Co-Fe@C promoters. Pd at 0.5 wt % somewhat enhances CO₂ conversion and CH₄ selectivity, probably due to H₂ activation and spillover on Co-Fe. At similar concentrations, Ce does not influence CO₂ conversion but does diminish CO selectivity. A 25 wt % Fe excess increases the Fe-Co particle size and has a detrimental effect due to this large particle size. The presence of 25 wt % of Ca increases the CO₂ conversion and CH₄ selectivity remarkably, the effect being attributable to the CO₂ adsorption capacity and basicity of Ca. Sulfur at a concentration of 2.1% or higher acts as a strong poison, decreasing CO₂ conversion and shifting selectivity to CO. The combination of S and alkali metals as promoters maintain the CO selectivity of S but notably increase the CO₂ conversion. Overall, this study shows how promoters and poisons can alter the catalytic activity of Co/Fe@C catalysts, changing from CH₄ to CO. It is expected that further modulation of the activity of Co/Fe@C catalysts can serve to drive the activity and selectivity of these materials to any CO₂ hydrogenation products that are wanted.

Boosting Oxygen Reduction via Integrated Construction and Synergistic Catalysis of Porous Platinum Alloy and Defective Graphitic Carbon

Integrated fabrication through the strong interaction between catalyst and carrier is crucial to realize efficient oxygen electrocatalysis for fuel cells. We report herein a porous Pt-rich alloy encapsulated by graphitic carbon via integration engineering, where a synergistic catalysis between ternary PtCuCo alloy and graphitic Co-N-C results in the optimized reaction pathway and improved oxygen reduction reaction (ORR) performance. The hybrid catalyst PtCuCo@Co-N-C delivers a mass activity of 1.14 A mg_Pt ^-1 at 0.9 V vs. RHE and a peak power density of 960 mW cm^-2 in the full-cell assessment, outperforming commercial Pt/C catalyst (0.12 A mg_Pt ^-1 and 780 mW cm^-2 ). Experimental results combined with theoretical simulations suggest that the mutual assistance between porous Pt alloy and Co-N-C accounts for the enhanced catalytic performance. Such integrated engineering concept is significant for strengthening the anti-corrosion capabilities and improving the ORR performance of Pt-based catalysts.

Laser Scribing Fabrication of Graphitic Carbon Biosensors for Label-Free Detection of Interleukin-6

Interleukin-6 (IL-6) is an important immuno-modulating cytokine playing a pivotal role in inflammatory processes in disease induction and progression. As IL-6 serves as an important indicator of disease state, it is of paramount importance to develop low cost, fast and sensitive improved methods of detection. Here we present an electrochemical immunosensor platform based on the use of highly porous graphitic carbon electrodes fabricated by direct laser writing of commercial polyimide tapes and chemically modified with capture IL-6 antibodies. The unique porous and 3D morphology, as well as the high density of edge planes of the graphitic carbon electrodes, resulted in a fast heterogeneous electron transfer (HET) rate, k⁰ = 0.13 cm/s. The resulting immunosensor showed a linear response to log of concentration in the working range of 10 to 500 pg/mL, and low limit of detection (LOD) of 5.1 pg/mL IL-6 in phosphate buffer saline. The total test time was approximately 90 min, faster than the time required for ELISA testing. Moreover, the assay did not require additional sample pre-concentration or labelling steps. The immunosensor shelf-life was long, with stable results obtained after 6 weeks of storage at 4 °C, and the selectivity was high, as no response was obtained in the presence of another inflammatory cytokine, Interlukin-4. These results show that laser-fabricated graphitic carbon electrodes can be used as selective and sensitive electrochemical immunosensors and offer a viable option for rapid and low-cost biomarker detection for point-of-care analysis.

Nanoporous Co and N-Codoped Carbon Composite Derived from ZIF-67 for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have nice prospects because of their excellent energy density and theoretical specific capacity. However, the dissolution of lithium polysulfides and shuttle effects lead to a low coulombic efficiency and cycle performance of Li-S batteries. Therefore, designing electrode materials that can suppress the shuttle effect and adsorb polysulfides is of great significance. In this work, a Co and N-codoped carbon composite via heating a type of Co-etched zeolitic imidazolate framework-67 (ZIF-67), nanocube precursor, in inert gas is reported as a cathode sulfur carrier material for Li-S batteries. The experimental results show that high-temperature carbonization results in mesoporous structures inside the material which not only provide ion channels for the reaction but also improve the adsorption capacity of polysulfides. Furthermore, the exposed metal Co sites and N atoms can also inhibit the shuttle effect. When the annealing temperature is 600 °C, the sulfur composite exhibits a good cycling stability and rate performance. The cathode showed an improved initial specific capability of 1042 and still maintained 477 mAh g⁻¹ at the rate of 1 C (1 C = 1672 mA g⁻¹). Furthermore, at 5 C, a stable specific discharge capacity of 608 mAh g⁻¹ was obtained.

Graphitic Carbon with MnO/Mn7 C3 Prepared by Laser-Scribing of MOF for Versatile Supercapacitor Electrodes

Pseudocapacitive materials encapsulated in conductive carbon matrix are of paramount importance to develop energy storage devices with high performance and long lifespan. Here, via simple laser-scribing, the Mn-based metal-organic framework [EG-MOF-74(Mn)] is transformed into pseudocapacitive hybrid MnO/Mn₇ C₃ encapsulated in highly conductive graphitic carbon. It is revealed that the rapid carbothermic reduction of MnO (C + MnO → C' + Mn₇ C₃ + CO) leads to the formation of the intermediate pseudocapacitive MnO/Mn₇ C₃ and the concurrent catalytic graphitization of disordered carbon. This reaction produces a new type of pseudocapacitive material in the form of MnO/Mn₇ C₃ fully embedded in highly conductive graphitic carbon. Thanks to the synergistic effect of the MnO/Mn₇ C₃ nanoparticles and the graphitic carbon, the composite exhibits a high specific capacitance of 403 F g^-1 with excellent stability. Asymmetric coin-cell supercapacitors based on the composite demonstrate high energy (29.2 Wh kg^-1 ) and power densities (8000 W kg^-1 ) with a long lifespan. Prototypes of flexible paper-based supercapacitors made of the composite also show great potential toward applications of flexible electronics.

Defects in Hard Carbon: Where Are They Located and How Does the Location Affect Alkaline Metal Storage?

Hard carbon anodes have shown significant promise for next-generation battery technologies. These nanoporous carbon materials are highly complex and vary in structure depending on synthesis method, precursors, and pyrolysis temperature. Structurally, hard carbons are shown to consist of disordered planar and curved motifs, which have a dramatic impact on anode performance. Here, the impact of position on defect formation energy is explored through density functional theory simulations, employing a mixed planar bulk and curved surface model. At defect sites close to the surface, a dramatic decrease ( ≥ 50%) in defect formation energy is observed for all defects except the nitrogen substitutional defect. These results confirm the experimentally observed enhanced defect concentration at surfaces. Previous studies have shown that defects have a marked impact on metal storage. This work explores the interplay between position and defect type for lithium, sodium, and potassium adsorption. Regardless of defect location, it is found that the energetic contributions to the metal adsorption energies are principally dictated by the defect type and carbon interlayer distance.

Multi-Elemental Electronic Coupling for Enhanced Hydrogen Generation

A robust polyaniline-assisted strategy is developed to construct a self-supported electrode constituting a nitrogen, phosphorus, sulfur tri-doped thin graphitic carbon layer encapsulated sulfur-doped molybdenum phosphide nanosheet array (NPSCL@S-MoP NSs/CC) with accessible nanopores, desirable chemical compositions, and stable composite structure for efficient hydrogen evolution reaction (HER). The multiple electronic coupling effects of S-MoP with N, P, S tri-dopants afford effective regulation on their electrocatalytic performance by endowing abundant accessible active sites, outstanding charge-transfer property, and d-band center downshift with a thermodynamically favorable hydrogen adsorption free energy (ΔG_H* ) for efficient hydrogen evolution catalysis. As a result, the NPSCL@S-MoP NSs/CC electrode exhibits overpotentials as low as 65, 114, and 49 mV at a geometric current density of 10 mA cm^-2 and small Tafel slopes of 49.5, 69.3, and 53.8 mV dec^-1 in 0.5 m H₂ SO₄ , 1.0 m PBS, and 1.0 m KOH, respectively, which could maintain 50 h of stable performance, almost outperforming all MoP-based catalysts reported so far. This study provides a valuable methodology to produce interacted multi-heteroatomic doped graphitic carbon-transition metal phosphide electrocatalysts with superior HER performance in a wide pH range.

Toward pH Independent Oxygen Reduction Reaction by Polydopamine Derived 3D Interconnected, Iron Carbide Embedded Graphitic Carbon

Recent advancements on the development of nonprecious electrocatalysts with iron (Fe) incorporated active centers have generated confidence on realizing cost-effective proton exchange membrane fuel cells (PEMFCs). However, most of these catalysts that emerged as a substitution for the platinum supported on carbon (Pt/C) catalysts in oxygen reduction reaction (ORR) are active under basic conditions, and their feasibility in PEMFCs remains as a challenge. In this scenario, this work reports the synthesis of a Pt-free oxygen reduction electrocatalyst prepared by the annealing of polydopamine grown melamine foam. The prepared catalyst has a three-dimensional (3D) interconnected bilayer network structure possessing the carbon nitride backbone wrapped by graphitic carbon layer bearing iron carbides and nitrides as the active centers (3D-FePDC). Interestingly, the 3D-FePDC catalyst displayed an ORR activity both under acidic and basic conditions. Whereas the ORR performance of 3D-FePDC closely matches that of the commercial Pt/C in the basic medium, it displays only a low overpotential value of 60 mV under acidic conditions compared to its Pt counterpart. The kinetics of ORR on 3D-FePDC is found to be similar to the four-electron (4e) reduction pathway displayed by Pt/C. Testing of a PEMFC in a single cell mode by using 3D-FePDC as the cathode catalyst and Nafion membrane delivered a maximum power density of 278 mW cm^-2, which is a promising value expected from a system based on the nonprecious metal cathode. Ultimately, as a cost-effective catalyst that can effectively perform irrespective of the pH conditions, 3D-FePDC offers significant prospects in the areas like fuel cells and metal-air batteries which work in acidic and/or basic conditions.

Effects of SiC and Resorcinol-Formaldehyde (RF) Carbon Coatings on Silicon-Flake-Based Anode of Lithium Ion Battery

Silicon flakes of about 100 × 1000 × 1000 nm in sizes recycled from wastes of silicon wafer manufacturing processes were coated with combined silicon carbide (SiC) and graphitic (Resorcinol-Formaldehyde (RF)) carbon coatings to serve as active materials of the anode of lithium ion battery (LIB). Thermal carbonization of silicon at 1000 °C for 5 h forms 5-nm SiC encapsulating silicon flakes. SiC provides physical strength to help silicon flakes maintain physical integrity and isolating silicon from irreversible reactions with the electrolyte. Lithium diffuses through SiC before alloying with silicon. The SiC buffer layer results in uniform alloying reactions between lithium and silicon on the surface around a silicon flake. RF carbon coatings provide enhanced electrical conductivity of SiC encapsulated silicon flakes. We characterized the coatings and anode by SEM, TEM, FTIR, XRD, cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and electrical resistance measurements. Coin half-cells with combined SiC and RF carbon coatings exhibit an initial Coulombic efficiency (ICE) of 76% and retains a specific capacity of 955 mAh/g at 100th cycle and 850 mAh/g at 150th cycle of repetitive discharge and charge operation. Pre-lithiation of the anode increases the ICE to 97%. The SiC buffer layer reduces local stresses caused by non-uniform volume changes and improves the capacity retention and the cycling life.

ZIF67@MFC-Derived Co/N-C@CNFs Interconnected Frameworks with Graphitic Carbon-Encapsulated Co Nanoparticles as Highly Stable and Efficient Electrocatalysts for Oxygen Reduction Reactions

Development of nonprecious metal catalysts for oxygen reduction reaction (ORR) to reduce or eliminate Pt-based electrocatalysts is of great importance for fuel cells. Herein, Co/N-codoped carbon with carbon nanofiber (CNF) interconnected three-dimensional (3D) frameworks and graphitic carbon-encapsulated Co nanoparticles were designed and successfully prepared via the in situ growth of zeolitic imidazolate framework-67 (ZIF67) with biomass nano-microfibrillar cellulose (MFC) and then pyrolysis. The catalyst (Co/N-C@CNFs) exhibited outstanding long-term catalytic durability with 92.7% current retention after 70 000 s, which was much higher than that of commercial Pt/C in alkaline media. The support and connection of CNFs to Co/N-C frameworks and the protection of Co nanoparticles by graphite layers contribute to their impressive long-term catalytic stability. Meanwhile, Co/C-N@CNFs displayed excellent ORR catalytic performance (E₀ = 0.952 V vs RHE, E_1/2 = 0.852 V vs RHE, and n: 4.2) in alkaline media. This strategy provides new insights into developing advanced nonprecious metal carbon-based catalysts for ORR.

Electrolyte-Dependent Sodium Ion Transport Behaviors in Hard Carbon Anode

A comprehensive study is conducted on hard carbon (HC) series samples by tuning the graphitic local microstructures systematically as an anode for SIBs in both carbonate- (CBE) and glyme-based electrolytes (GBE). The results reveal more detailed charge storage characters of HCs on the LVP section. 1) The LVP capacity is closely related to the prismatic surface area to the basal plane as well as the bulk density, regardless of electrolyte systems. 2) The glyme-sodium ion complex can facilitate sodium ion delivery into the internal closed pores of the HCs along with not well-ordered graphitic structures. 3) The glyme-mediated sodium ion-storage behavior causes significant decreases in both surface film resistance and charge transfer resistance, leading to enhanced rate capability. 4) The LVP originates from the formation of pseudo-metallic sodium nanoclusters, which are the same in a CBE and GBE. These results provide insight into the sodium ion-storage behaviors of HCs, particularly on the interrelationship between graphitic local microstructures and electrolyte systems. In addition, a high-performance HC anode with a plateau capacity of ≈300 mA h g^-1 is designed based on the information, and its workability is demonstrated in a full-cell SIB device.

A Review of the Effect of a Nanostructured Thin Film Formed by Titanium Carbide and Titanium Oxides Clustered around Carbon in Graphitic Form on Osseointegration

Improving the biocompatibility of implants is an extremely important step towards improving their quality. In this review, we recount the technological and biological process for coating implants with thin films enriched in titanium carbide (TiC), which provide improved cell growth and osseointegration. At first, we discuss the use of a Pulsed Laser Ablation Deposition, which produced films with a good biocompatibility, cellular stimulation and osseointegration. We then describe how Ion Plating Plasma Assisted technology could be used to produce a nanostructured layer composed by graphitic carbon, whose biocompatibility is enhanced by titanium oxides and titanium carbide. In both cases, the nanostructured coating was compact and strongly bound to the bulk titanium, thus particularly useful to protect implants from the harsh oxidizing environment of biological tissues. The morphology and chemistry of the nanostructured coating were particularly desirable for osteoblasts, resulting in improved proliferation and differentiation. The cellular adhesion to the TiC-coated substrates was much stronger than to uncoated surfaces, and the number of philopodia and lamellipodia developed by the cells grown on the TiC-coated samples was higher. Finally, tests performed on rabbits confirmed in vivo that the osseointegration process of the TiC-coated implants is more efficient than that of uncoated titanium implants.

Synthesis of Porous Biochar Containing Graphitic Carbon Derived From Lignin Content of Forestry Biomass and Its Application for the Removal of Diclofenac Sodium From Aqueous Solution

Porous biochar containing graphitic carbon materials have received great attention from various disciplines, especially for environmental pollutant treatment, due to their cost-effective and specific textural properties. This study exhibited a two-step strategy to compose lignin-porous biochar containing graphitic carbon (LPGC) from pitch pine sawdust and investigated its adsorptive removal for diclofenac sodium (DCF) from an aqueous solution. Sulfuric acid (H2SO4) was utilized to obtain lignin content from biomass and potassium ferrate (K2FeO4) and was adopted to fulfill the synchronous carbonization and graphitization of LPGC. Through slow pyrolysis in atmospheric N2 (900°C - 2 h), the structure of the as-prepared sample was successfully modified. Using SEM images, a stripped layer structure was observed on the H2SO4-treated sample for both one-step and two-step activated samples, indicating the pronounced effect of H2SO4 in the layering of materials. K2FeO4 acted as an activator and catalyst to convert biomass into the porous graphitic structure. The BET surface area, XRD and Raman spectra analyses demonstrated that LPGC possessed a micro/mesoporous structure with a relatively large surface area (457.4 m2 g-1) as well as the presence of a graphitic structure. Further adsorption experiments revealed that LPGC exhibited a high DCF adsorption capacity (qmax = 159.7 mg g-1 at 298 K, pH = 6.5). The effects of ambient conditions such as contact time, solution pH, temperature, ionic strength, electrolyte background on the uptake of DCF were investigated by a batch adsorption experiment. Results indicated that the experimental data were best fitted with the pseudo second-order model and Langmuir isotherm model. Furthermore, the adsorption of DCF onto the LPGC process was spontaneous and endothermic. Electrostatic interaction, H-bonding interaction, and π-π interaction are the possible adsorption mechanisms. The porous biochar containing graphitic carbon obtained from the lignin content of pitch pine sawdust may be a potential material for eliminating organic pollutants from water bodies.

Mechanical Properties of 3D Nanostructures Obtained by Focused Electron/Ion Beam-Induced Deposition: A Review

This article reviews the state-of-the -art of mechanical material properties and measurement methods of nanostructures obtained by two nanoscale additive manufacturing methods: gas-assisted focused electron and focused ion beam-induced deposition using volatile organic and organometallic precursors. Gas-assisted focused electron and ion beam-induced deposition-based additive manufacturing technologies enable the direct-write fabrication of complex 3D nanostructures with feature dimensions below 50 nm, pore-free and nanometer-smooth high-fidelity surfaces, and an increasing flexibility in choice of materials via novel precursors. We discuss the principles, possibilities, and literature proven examples related to the mechanical properties of such 3D nanoobjects. Most materials fabricated via these approaches reveal a metal matrix composition with metallic nanograins embedded in a carbonaceous matrix. By that, specific material functionalities, such as magnetic, electrical, or optical can be largely independently tuned with respect to mechanical properties governed mostly by the matrix. The carbonaceous matrix can be precisely tuned via electron and/or ion beam irradiation with respect to the carbon network, carbon hybridization, and volatile element content and thus take mechanical properties ranging from polymeric-like over amorphous-like toward diamond-like behavior. Such metal matrix nanostructures open up entirely new applications, which exploit their full potential in combination with the unique 3D additive manufacturing capabilities at the nanoscale.

Stabilizing Metallic Iron Nanoparticles by Conformal Graphitic Carbon Coating for High-Rate Anode in Ni-Fe Batteries

Nickel-iron (Ni-Fe) batteries are promising candidates for large-scale energy storage due to their high safety and low cost. However, their power density and cycling efficiency remain limited by the poor kinetics of the Fe anode. Herein, we report high-performance Fe anodes based on active Fe nanoparticles conformally coated with carbon shells, which were synthesized from low-cost precursors using a scalable process. Such core-shell structured C-Fe anodes offer high electrochemical activity and stability. Specifically, a high specific capacity of 208 mAh g^-1 at a current density of 1 A g^-1 (based on the total weight of Fe and C) and a capacity retention of 93% after 2000 cycles at 4 A g^-1 can be achieved. When coupled with a Ni cathode, such a full cell battery can deliver a high energy density of 101.0 Wh kg^-1 at power density of 0.81 kW kg^-1 and 51.6 Wh kg^-1 at 8.2 kW kg^-1 (based on the mass of the electrode materials), among the best energy and power performance among Ni-Fe batteries reported results. Thus, this work may provide an effective and scalable route toward high-performance anodes for high-power and long-life Ni-Fe batteries.

Silicon-Core-Carbon-Shell Nanoparticles for Lithium-Ion Batteries: Rational Comparison between Amorphous and Graphitic Carbon Coatings

Silicon-core-carbon-shell nanoparticles have been widely studied as promising candidates for the replacement of graphite in commercial lithium-ion batteries. Over more than 10 years of R&D, the many groups actively working in this field have proposed a profusion of distinctive nanomaterial designs. This broad variety makes it extremely challenging to establish mechanistic insight into how fundamental material structure and properties affect battery performance. In particular, the interplay between the character of the carbon encapsulation layer and the electrochemical performance of the composite is still poorly understood. In this work, we aim to address this lack of knowledge through the development of a modified chemical vapor deposition approach that enables precise control of the degree of graphitization of the carbon coating. We provide a comparison between core-shell structures maintaining identical silicon cores with different types of carbon shells, that is, graphitic carbon and amorphous carbon. A highly graphitic carbon layer is not only characterized by higher electrical conductivity but markedly favors the transport of lithium ions into the silicon core with respect to an amorphous one. This advantageous property confers better cycling stability to the composite material. We also demonstrate that the graphitic-carbon-coated particles display excellent electrochemical performance even when used as a simple "drop-in" additive in graphite-dominant anodes for current generation Li-ion batteries. Replacement of 10% by weight of graphite in the electrode composition results in an increase of 60% in the storage capacity with a first cycle Coulombic efficiency of 91% and capacity retention over 100 cycles of 86%.

Interfacing Manganese Oxide and Cobalt in Porous Graphitic Carbon Polyhedrons Boosts Oxygen Electrocatalysis for Zn-Air Batteries

Rational design and synthesis of highly active and robust bifunctional non-noble electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required for efficient rechargeable metal-air batteries. Herein, abundant MnO/Co heterointerfaces are engineered in porous graphitic carbon (MnO/Co/PGC) polyhedrons via a facile hydrothermal-calcination route with a bimetal-organic framework as the precursor. The in situ generated Co nanocrystals not only create well-defined heterointerfaces with high conductivity to overcome the poor OER activity but also promote the formation of robust graphitic carbon. Owing to the desired composition and formation of the heterostructures, the resulting MnO/Co/PGC exhibits superior activity and stability toward both OER and ORR, which makes it an efficient air cathode for the rechargeable Zn-air battery. Importantly, the homemade Zn-air battery is able to deliver excellent performance including a peak power density of 172 mW cm^-2 and a specific capacity of 872 mAh g^-1 , as well as excellent cycling stability (350 cycles), outperforming commercial mixed Pt/C||RuO₂ catalysts. This work highlights the synergy from heterointerfaces in oxygen electrocatalysis, thus providing a promising approach for advanced metal-air cathode materials.

Ordered Mesoporous Graphitic Carbon/Iron Carbide Composites with High Porosity as a Sulfur Host for Li-S Batteries

The lithium-sulfur battery (LSB) is a promising candidate for future energy storage but faces technological challenges including the low electronic conductivity of sulfur and the solubility of intermediates during cycling. Additionally, current host materials often lack sufficient conductivity and porosity to raise the sulfur loading to over 80 wt %. Here, ordered mesoporous graphitic carbon/iron carbide nanocomposites were prepared via an evaporation-induced self-assembly process using soluble resol, prehydrolyzed tetraethyl orthosilicate (TEOS), and iron(III) chloride as the carbon, silica (SiO₂), and iron precursors, respectively. Graphitization and SiO₂ etching were conducted simultaneously via Teflon-assisted, solid-state decomposition at high temperature. A high surface area (∼3100 m² g^-1), large pore volume (∼3.3 cm³ g^-1), and graphitized carbon frame were achieved, giving a high sulfur loading (85 wt %) while tolerating volumetric expansion during discharge. Electrochemical testing of a LSB containing the composite/sulfur cathode exhibited a superior reversible capacity exceeding 1300 mAh g^-1 at a moderate current (C/10) and a low decay in capacity of 9% after 500 cycles at C/5. The interaction between mesoporous graphitic carbon and sulfur is proposed.

Improving control of carbide-derived carbon microstructure by immobilization of a transition-metal catalyst within the shell of carbide/carbon core-shell structures

Carbon materials for electrical energy devices, such as battery electrodes or fuel-cell catalysts, require the combination of the contradicting properties of graphitic microstructure and porosity. The usage of graphitization catalysts during the synthesis of carbide-derived carbon materials results in materials that combine the required properties, but controlling the microstructure during synthesis remains a challenge. In this work, the controllability of the synthesis route is enhanced by immobilizing the transition-metal graphitization catalyst on a porous carbon shell covering the carbide precursor prior to conversion of the carbide core to carbon. The catalyst loading was varied and the influence on the final material properties was characterized by using physisorption analysis with nitrogen as well as carbon dioxide, X-ray diffraction, temperature-programmed oxidation (TPO), Raman spectroscopy, SEM and TEM. The results showed that this improved route allows one to greatly vary the crystallinity and pore structure of the resulting carbide-derived carbon materials. In this sense, the content of graphitic carbon could be varied from 10-90 wt % as estimated from TPO measurements and resulting in a specific surface area ranging from 1500 to 300 m²·g^-1.

Polynuclear Complexes as Precursor Templates for Hierarchical Microporous Graphitic Carbon: An Unusual Approach

A highly porous carbon was synthesized using a coordination complex as an unusual precursor. During controlled pyrolysis, a trinuclear copper complex, [Cu^II₃Cl₄(H₂L)₂]·CH₃OH, undergoes phase changes with melt and expulsion of different gases to produce a unique morphology of copper-doped carbon which, upon acid treatment, produces highly porous graphitic carbon with a surface area of 857 m² g^-1 and a gravimetric hydrogen uptake of 1.1 wt % at 0.5 bar pressure at 77 K.

Highly Graphitic Mesoporous Fe,N-Doped Carbon Materials for Oxygen Reduction Electrochemical Catalysts

The synthesis, characterization, and electrocatalytic properties of mesoporous carbon materials doped with nitrogen atoms and iron are reported and compared for the catalyzed reduction of oxygen gas at fuel cell cathodes. Mixtures of common and inexpensive organic precursors, melamine, and formaldehyde were pyrolyzed in the presence of transition-metal salts (e.g., nitrates) within a mesoporous silica template to yield mesoporous carbon materials with greater extents of graphitization than those of others prepared from small-molecule precursors. In particular, Fe,N-doped carbon materials possessed high surface areas (∼800 m²/g) and high electrical conductivities (∼19 S/cm), which make them attractive for electrocatalyst applications. The surface compositions of the mesoporous Fe,N-doped carbon materials were postsynthetically modified by acid washing and followed by high-temperature thermal treatments, which were shown by X-ray photoelectron spectroscopy to favor the formation of graphitic and pyridinic nitrogen moieties. Such surface-modified materials exhibited high electrocatalytic oxygen reduction activities under alkaline conditions, as established by their high onset and half-wave potentials (1.04 and 0.87 V, respectively vs reversible hydrogen electrode) and low Tafel slope (53 mV/decade). These values are superior to many similar transition-metal- and N-doped carbon materials and compare favorably with commercially available precious-metal catalysts, e.g., 20 wt % Pt supported on activated carbon. The analyses indicate that inexpensive mesoporous Fe,N-doped carbon materials are promising alternatives to precious metal-containing catalysts for electrochemical reduction of oxygen in polymer electrolyte fuel cells.

Cobalt Sulfide Nanowires Core Encapsulated by a N, S Codoped Graphitic Carbon Shell for Efficient Oxygen Reduction Reaction

Exploration of economical electrocatalysts for highly efficient and stable oxygen reduction reaction (ORR) is believed to be essential for diverse future renewable energy applications. Herein, cobalt sulfide nanowire core encapsulated in a N, S codoped graphitic carbon shell (CoS NWs@NSC) is successfully fabricated via the calcination of polydopamine-coated Co(CO₃ )_0.5 (OH)_0.11 H₂ O NWs with sulfur powder under argon atmosphere. The uniform encapsulation of CoS core by N, S codoped graphitic carbon shell favors the interaction of the core-shell structure for generating stable and numerous ORR active sites homogeneously dispersed throughout the materials. Meanwhile, the wire-like CoS NWs@NSC stacks to form 3D mesoporous conductive networks, which improves the mass and charge transport capability of catalyst. Accordingly, the resultant CoS NWs@NSC electrocatalysts possess excellent ORR activity through the four-electron pathway with superior stability and methanol tolerance over the Pt/C in 0.1 m KOH. This strategy can offer inspiration for designing and fabricating novel core-shell-structured nanomaterials with active sites derived from uniform morphology as potential electrocatalysts for various vital renewable energy devices.

Electrocatalytic N-Doped Graphitic Nanofiber - Metal/Metal Oxide Nanoparticle Composites

Carbon-based nanocomposites have shown promising results in replacing commercial Pt/C as high-performance, low cost, nonprecious metal-based oxygen reduction reaction (ORR) catalysts. Developing unique nanostructures of active components (e.g., metal oxides) and carbon materials is essential for their application in next generation electrode materials for fuel cells and metal-air batteries. Herein, a general approach for the production of 1D porous nitrogen-doped graphitic carbon fibers embedded with active ORR components, (M/MO_x , i.e., metal or metal oxide nanoparticles) using a facile two-step electrospinning and annealing process is reported. Metal nanoparticles/nanoclusters nucleate within the polymer nanofibers and subsequently catalyze graphitization of the surrounding polymer matrix and following oxidation, create an interconnected graphite-metal oxide framework with large pore channels, considerable active sites, and high specific surface area. The metal/metal oxide@N-doped graphitic carbon fibers, especially Co₃ O₄ , exhibit comparable ORR catalytic activity but superior stability and methanol tolerance versus Pt in alkaline solutions, which can be ascribed to the synergistic chemical coupling effects between Co₃ O₄ and robust 1D porous structures composed of interconnected N-doped graphitic nanocarbon rings. This finding provides a novel insight into the design of functional electrocatalysts using electrospun carbon nanomaterials for their application in energy storage and conversion fields.

Oil Palm Waste-Based Precursors as a Renewable and Economical Carbon Sources for the Preparation of Reduced Graphene Oxide from Graphene Oxide

Herein, a new approach was proposed to produce reduced graphene oxide (rGO) from graphene oxide (GO) using various oil palm wastes: oil palm leaves (OPL), palm kernel shells (PKS) and empty fruit bunches (EFB). The effect of heating temperature on the formation of graphitic carbon and the yield was examined prior to the GO and rGO synthesis. Carbonization of the starting materials was conducted in a furnace under nitrogen gas for 3 h at temperatures ranging from 400 to 900 °C and a constant heating rate of 10 °C/min. The GO was further synthesized from the as-carbonized materials using the ‘improved synthesis of graphene oxide’ method. Subsequently, the GO was reduced by low-temperature annealing reduction at 300 °C in a furnace under nitrogen gas for 1 h. The I_G/I_D ratio calculated from the Raman study increases with the increasing of the degree of the graphitization in the order of rGO from oil palm leaves (rGOOPL) < rGO palm kernel shells (rGOPKS) < rGO commercial graphite (rGOCG) < rGO empty fruit bunches (rGOEFB) with the I_G/I_D values of 1.06, 1.14, 1.16 and 1.20, respectively. The surface area and pore volume analyses of the as-prepared materials were performed using the Brunauer Emmett Teller-Nitrogen (BET-N₂) adsorption-desorption isotherms method. The lower BET surface area of 8 and 15 m² g⁻¹ observed for rGOCG and rGOOPL, respectively could be due to partial restacking of GO layers and locally-blocked pores. Relatively, this lower BET surface area is inconsequential when compared to rGOPKS and rGOEFB, which have a surface area of 114 and 117 m² g⁻¹, respectively.

Graphitic Nanocarbon-Selenium Cathode with Favorable Rate Capability for Li-Se Batteries

A well-organized selenium/carbon nanosheets nanocomposite(Se/CNSs) is prepared by confining chain-like Se_n molecules in hierarchically micromesoporous carbon nanosheets. A unique two-dimensional morphology and high graphitization degree of carbon nanosheets benefits fast Li⁺/e^- access to the active Se, which guarantees a high utilization of Se during the(de)lithiation process. Besides, the chain-like Se molecules confined in the carbon matrix could alleviate the shuttle effect of polyselenides and promise a stable electrochemistry. Therefore, the resultant Se/CNSs delivers a highly reversible capacity, a long cycle life and favorable rate capabilities. Furthermore, a Li-Se pouch cell built from a metallic Li anode and the as-prepared Se/CNSs cathode exhibits an excellent electrochemical performance, demonstrating the potential of Se/CNSs in serving future energy storage devices with high energy density.

Self-Anticoking of a Cobalt Surface by Subsurface Oxygen in the Fischer-Tropsch Synthesis

Understanding the fundamental processes taking place on Co surfaces during the Fischer-Tropsch (FT) synthesis is of great interest and importance. We herein report a self-anticoking mechanism of a cobalt surface by subsurface oxygen. The active carbidic carbon species for FT synthesis tends to transform into the inactive graphitic carbon species on clean Co(0001) and poisons the Co surface. Subsurface atomic oxygen on Co(0001) can stabilize the active carbidic carbon species and quench the transformation process. These results reveal, to the best of our knowledge, for the first time the reactivity of various surface species on Co surfaces that dynamically maintain a delicate balance to enhance the long-term stability of Co catalysts during FT synthesis.

Enhancement of the Rate Capability of LiFePO4 by a New Highly Graphitic Carbon-Coating Method

Low lithium ion diffusivity and poor electronic conductivity are two major drawbacks for the wide application of LiFePO4 in high-power lithium ion batteries. In this work, we report a facile and efficient carbon-coating method to prepare LiFePO4/graphitic carbon composites by in situ carbonization of perylene-3,4,9,10-tetracarboxylic dianhydride during calcination. Perylene-3,4,9,10-tetracarboxylic dianhydride containing naphthalene rings can be easily converted to highly graphitic carbon during thermal treatment. The ultrathin layer of highly graphitic carbon coating drastically increased the electronic conductivity of LiFePO4. The short pathway along the [010] direction of LiFePO4 nanoplates could decrease the Li(+) ion diffusion path. In favor of the high electronic conductivity and short lithium ion diffusion distance, the LiFePO4/graphitic carbon composites exhibit an excellent cycling stability at high current rates at room temperature and superior performance at low temperature (-20 °C).

Formation of nitrogen-doped mesoporous graphitic carbon with the help of melamine

An efficient and facile synthesis method of nitrogen-doped mesoporous graphitic carbon (NMGC) was reported with melamine as a nitrogen source and citric acid as a carbon source. By taking advantage of the functional groups on melamine and citric acid, a uniform mixture of these two components was obtained via a self-assembly process. Accordingly, the nitrogen-doped mesoporous graphitic carbon (NMGC) can be obtained by means of the high temperature treatment. This as-prepared NMGC showed a promising potential as an anode material in lithium-ion batteries.

Dialytic Separation of Bundled, Functionalized Carbon Nanotubes from Carbonaceous Impurities

Separating functionalized single-wall carbon nanotubes (SWCNTs) from functionalized amorphous carbon is challenging, due to their polydispersity and similar physicochemical properties. We describe a single-step, dialytic separation method that takes advantage of the ability of heavily functionalized SWCNTs to bundle in a polar environment while maintaining their solubility. Experiments on functionalized SWCNTs were compared with functionalized, C60 fullerenes (buckyballs) to probe the general applicability of the method and further characterize the bundling process. This approach may simultaneously be used to purify a functionalization reaction mixture of unreacted small molecules and of residual solvents, such as dimethylformamide.

Sulfur/graphitic hollow carbon sphere nano-composite as a cathode material for high-power lithium-sulfur battery

The intrinsic low conductivity of sulfur which leads to a low performance at a high current rate is one of the most limiting factors for the commercialization of lithium-sulfur battery. Here, we present an easy and convenient method to synthesize a mono-dispersed hollow carbon sphere with a thin graphitic wall which can be utilized as a support with a good electrical conductivity for the preparation of sulfur/carbon nano-composite cathode. The hollow carbon sphere was prepared from the pyrolysis of the homogenous mixture of the mono-dispersed spherical silica and Fe-phthalocyanine powder in elevated temperature. The composite cathode was manufactured by infiltrating sulfur melt into the inner side of the graphitic wall. The electrochemical cycling shows a capacity of 425 mAh g-1 at 3 C current rate which is more than five times larger than that for the sulfur/carbon black nano-composite prepared by simple ball milling.

Graphitic carbon grown on fluorides by molecular beam epitaxy

We study the growth mechanism of carbon molecules supplied by molecular beam epitaxy on fluoride substrates (MgF2, CaF2, and BaF2). All the carbon layers form graphitic carbon with different crystallinities depending on the cation. Especially, the growth on MgF2 results in the formation of nanocrystalline graphite (NCG). Such dependence on the cation is a new observation and calls for further systematic studies with other series of substrates. At the same growth temperature, the NCG on MgF2 has larger clusters than those on oxides. This is contrary to the general expectation because the bond strength of the carbon-fluorine bond is larger than that of the carbon-oxygen bond. Our results show that the growth of graphitic carbon does not simply depend on the chemical bonding between the carbon and the anion in the substrate.