Thin Carbon Layer Research Articles

Enhanced non-enzymatic glucose sensing of Cu–BTC-derived porous copper@carbon agglomerate

Porous copper@carbon agglomerate (PCCA) is prepared by pyrolysis of Cu3(BTC)2·3H2O (Cu–BTC, BTC = 1,3,5-benzenetricarboxylic acid) in 5% H2–N2 mixture atmosphere. The phase and morphology evolution are thoroughly examined by XRD, Raman, BET, TG, XPS, SEM and TEM, respectively. The results show that PCCA is formed at 400 °C and maintains the cubic morphology of the original Cu–BTC crystal. PCCA is composed by round-shaped copper nanoparticles that covered outside by thin layer of carbon. The non-enzymatic glucose sensing properties of PCCA-modified glassy carbon electrode (Cu/GCE) are characterized by cyclic voltammetry. The sensor shows high sensitivity of 614.3 µA mM−1 to glucose oxidation and negligible responses toward interference from uric acid, ascorbic acid, dopamine and l-cysteine at the level of their physiological concentrations. The sensor also exhibits rapid response (< 6 s), wide linear range (up to 3.33 mM) and low detection limit (0.29 µM at signal/noise ratio (S/N) = 3). Finally, the good stability, reproducibility and repeatability to glucose detection make PCCA a promising catalyst for non-enzymatic glucose sensor.

Porous NaTi2(PO4)3 nanoparticles coated with a thin carbon layer for sodium-ion batteries with enhanced rate and cycling performance

Exploring suitable electrode materials with high rate capability and long-term cycling stability for sodium-ion batteries (SIBs) is of great importance but still challenging. In this work, we report a facile strategy to synthesize the nanocomposite of porous NaTi2(PO4)3 nanoparticles coated with a thin carbon layer (NTP/C). The unique structural and component merits endow the NTP/C nanocomposite with excellent charge transfer kinetics and enhanced structural stability. Compared with the pristine NTP nanoparticles, the NTP/C nanocomposite exhibits significant enhanced rate capability (108.9 mA h g−1 at 0.2C and 55.0 mA h g−1 at 20C) and long-term cycling performance (capacity retention of 78.8% after 2000 cycles at 10C). The electrochemical results indicate the NTP/C nanocomposite could be a high-performance anode material for SIBs.

Mesoporous perforated Co3O4 nanoparticles with a thin carbon layer for high performance Li-ion battery anodes

A facile method for preparing mesoporous perforated Co3O4 nanoparticles with hollow channels and a thin carbon layer was newly designed and achieved with sacrificial carbon nanotube (CNT) templates. The threaded Co3O4 nanoparticles on the CNTs were fabricated through a hybridization process, and a subsequent calcination process produced mesoporous perforated Co3O4 nanoparticles. With a finely tuned calcination, CNTs were sacrificed to generate hollow channels in the Co3O4 nanoparticles and to provide a carbon source for the formation of a few nm-thick carbon layer on the surface of the Co3O4 nanoparticles simultaneously. The prepared mesoporous perforated Co3O4 nanoparticles with a robust electronic conductive layer enabled not only an enhanced electrochemical reactivity from the greatly increased contact area between the electrolyte and electrode but also a high electronic conductivity of the overall electrode so that excellent electrochemical performances (1115.1 mA h g−1 after 100 cycles; 595.9 mA h g−1 @ 5 C rate) were successfully achieved in the anode application of a lithium-ion battery.

Boosting Pt oxygen reduction reaction activity and durability by carbon semi-coated titania nanorods for proton exchange membrane fuel cells

We report a simple, scalable approach to improve interfacial characteristics of carbon semi-coated titania nanorods-supported-Pt with superior peak power density as compared to Pt/C with thin metal loading of 150 μg cm−2. Thin layer of carbon coated titania nanorod is synthesized by hydrothermal method. Carbon coated titania nanorods boosts the Pt oxygen reduction reaction activity than carbon. The crystal structure, dispersion of platinum nanoparticles, surface morphology and oxidation state are studied by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. Studies using conventional three electrode setup shows that Pt/CCT-30 retains 48% of initial electrochemical surface area even after 40,000 potential cycles between 0.6 and 1.2 V. The solid fuel cell mode accelerated stress durability studies show that thin layer of carbon coated titania nanorods-Pt (Pt/CCT 30) significantly enhances stability and preserves 75% of initial fuel cell performance even after 10,000 potential cycles between 1 and 1.5 V. In comparison, only 20% of performance is retained for Pt supported on carbon after 3000 cycles.

Tailoring the porous structure of N-doped carbon for increased oxygen reduction reaction activity

A facile one-pot method using molten salt medium is developed to fabricate an open structured N-doped carbon (ONC) derived from biomass. SEM and TEM show the ONC is made up of interconnected thin amorphous carbon layers. N2 isotherm shows that ONC has hierarchical porous structure with a high specific surface area of 1893.5m2g−1. Compared to commercial Pt/C (20wt%), the ONC has comparable ORR activity and better durability. Due to its high ORR activity and durability, producing an opened N-doped carbon in this molten salt medium can provide a promising approach for synthesizing heteroatom doped carbons with electrochemical performance.

ZnO/rGO/C composites derived from metal–organic framework as advanced anode materials for Li-ion and Na-ion batteries

A novel ZnO/reduced graphene oxide/carbon (ZnO/rGO/C) composite is synthesized by pyrolysis of Zn-based metal–organic framework where graphene oxide and the glucose are imported as carbon sources. As a result, ZnO nanoparticles dispersing on a uniform reduced graphene sheet with a thin carbon layer construct a unique structure, which can prevent the aggregation of ZnO, enhance the electronic conductivity, and offer a robust scaffold during electrochemical processes. Compared to the bare ZnO and ZnO/rGO, the obtained ZnO/rGO/C composite can exhibit a high reversible capacity (~ 830 mA h g−1 after 100 cycles, approximately 85% of theoretical capacity), and superior rate capability as anodes for Li-ion battery. Additionally, the electrochemical property of ZnO-based materials for Na-ion batteries is also proposed for the first time. It demonstrates that the as-synthesized ZnO/rGO/C composite also delivers an outperformance cyclic stability and considerable reversible capacity (~ 300 mA h g−1 after 100 cycles). This simple methodology can be further extended to other energy storage applications.

Carbon-coated single-crystalline LiMn2O4 nanowires synthesized by high-temperature solid-state reaction with high capacity for Li-ion battery

It is a challenge to synthesize highly crystalline nanomorphologies under high-temperature environments. Here, we report that carbon-coated single-crystal LiMn2O4 nanowires were obtained via a high-temperature solid-state method under air environment using carbon-coated MnO2 as the precursor. Without the coated layer of carbon, the obtained LiMn2O4 is bulk. The carbon layer coating on MnO2 acts as a space-limiting layer to maintain the nanowire morphology of the final product of LiMn2O4 during the reaction. Owing to the merits of the highly crystalline, 1D nanowire morphology and the close-coated thin carbon layer, the produced LiMn2O4@C nanowires deliver large capacity and long-term cycling stability. In addition, the space-limiting role of the carbon layer was also found to function for LiMn2O4@C sphere. It is a general strategy to obtain ternary nanomaterials with high crystallinity.

Ni nanoparticles decorated onto graphene oxide with SiO2 as interlayer for high performance on histidine-rich protein separation

Sandwich-like structure of graphene oxide (GO) @SiO2@C-Ni nanosheets were prepared by combining an extended stöber method with subsequent carbonization treatment, in which polydopamine was used as reducing agent and carbon source. Firstly, the GO nanosheets were covered with SiO2 interlayer and finally coated with a outer shell of nickel ion doped polydopamine (PDA-Ni2+) with an extended stöber method. Followed by a carbonization to produce the GO@SiO2@C-Ni sheets with metallic nickel nanoparticles embedded in PDA-derived thin graphic carbon layer. Notably, silica interlayer played a vital role in the formation of such GO@SiO2@C-Ni sheets. Without the protection of SiO2, the hydrophobic graphene@C-Ni composites were obtained instead. While with silica layer as the spacer, the obtained hydrophilic GO@SiO2@C-Ni composites were not only well dispersed in the solution, but also can be adjusted in terms of the size and density of Ni nanoparticles (NPs) on surface by changing the calcination temperature or the molar ratio between dopamine and nickel salt. Furthermore, nickel nanoparticles decorated on GO@SiO2 sheets were employed to enrich His-rich proteins (BHb and BSA) via specific metal affinity force between polyhistidine groups and nickel nanoparticles.

High-temperature reaction of sodium vapour with quartz glass

Heat pipes are one of the most efficient ways to transfer thermal energy hundred times more efficiently than copper. In this work, we present the investigation of sodium terminal velocity inside a glass pulsating heat pipe. Velocity measurements were conducted under operating conditions within the range of 500 – 1 100 °C. Since sodium is generally able to etch glass and ceramic materials, its presence resulted in glass reduction and sodium oxidation. From the XPS analysis of specimens extracted from a glass pipe after sodium explosion, it can be concluded that the reaction products are sodium oxide Na2O and a thin layer of carbon, which is localized on the SiO2 glass. The character of damage induced by chemical reactions is analysed in this manuscript.

Cobalt nickel nitride coated by a thin carbon layer anchoring on nitrogen-doped carbon nanotube anodes for high-performance lithium-ion batteries

We report a new material and a structural configuration for lithium-ion batteries consisting of cobalt nickel nitride coated by a thin carbon layer anchoring on nitrogen-doped carbon nanotubes. The anode delivers excellent lithium storage properties.

Size tunable carbon-encapsulated nickel nanoparticles synthesized by pyrolysis of nickel acetate tetrahydrate

In this study, size control of carbon-encapsulated nickel nanoparticles (CENiNPs) synthesized by direct thermal decomposition of Ni(CH3COO)2.4H2O (NiAc) was possible by varying systematically the initial amount of the precursor during its pyrolysis. The reaction was conducted inside a thermogravimetric analyzer coupled to a quadrupole mass spectrometer for evolved gas analysis. By heating non-isothermally different initial amounts of NiAc (100–400 mg) in an argon flow at 10 °C/min from room temperature to 500 °C, CENiNPs were readily obtained, in which a thin layer of carbon resulting from the breakdown of the anion protects their metallic core from spontaneous oxidation. High resolution transmission electron microscopy and methane catalytic decomposition tests revealed that this encapsulating layer can also exert a significant role in the control of the size distribution (40–140 nm) and catalytic activity of the resultant CENiNPs. Temperature programmed oxidation of the CENiNPs identified preliminary some surface carbon species responsible for the packing of the catalytically-active metallic core. This simple and cost-effective method emerges as a competitive way to manufacture and conserve highly active CENiNPs.

Graphene-Directed Formation of a Nitrogen-Doped Porous Carbon Sheet with High Catalytic Performance for the Oxygen Reduction Reaction

A nitrogen (N)-doped porous carbon sheet is prepared by in situ polymerization of pyrrole on both sides of graphene oxide, following which the polypyrrole layers are then transformed to the N-doped porous carbon layers during the following carbonization, and a sandwich structure is formed. Such a sheet-like structure possesses a high specific surface area and, more importantly, guarantees the sufficient utilization of the N-doping active porous sites. The internal graphene layer acts as an excellent electron pathway, and meanwhile, the external thin and porous carbon layer helps to decrease the ion diffusion resistance during electrochemical reactions. As a result, this sandwich structure exhibits prominent catalytic activity toward the oxygen reduction reaction in alkaline media, as evidenced by a more positive onset potential, a larger diffusion-limited current, better durability and poison-tolerance than commercial Pt/C. This study shows a novel method of using graphene to template the traditional porous carbon into a two-dimensional, thin, and porous carbon sheet, which greatly increases the specific surface area and boosts the utilization of inner active sites with suppressed mass diffusion resistance.

Sb Nanoparticles Anchored on Nitrogen-Doped Amorphous Carbon-Coated Ultrathin CoSx Nanosheets for Excellent Performance in Lithium-Ion Batteries.

Compared to single-component materials, hybrid materials with various components display superior electrochemical performance. In this work, two-dimensional CoSx@NC@Sb nanosheets assembled by ultrathin CoSx nanosheets (∼4 nm) and a thin layer of N-doped amorphous carbon (NC) combined with colloidlike Sb nanoparticles are designed and synthesized via a solvothermal route accompanied by a carbonization and Sb deposition procedure. If applied in lithium-ion batteries (LIBs), the hybrids exhibit a specific capacity of 960 mA h g-1 at the 100th cycle at 0.1 A g-1. Moreover, the reversible capacity still maintains at 494 mA h g-1 after 500 cycles at a high rate of 10 A g-1. All enhanced electrochemical properties of the hybrids are attributed to the synergistic effect of the two components and their unique structural features, which can effectively increase the electrical conductivity, shorten the pathway of Li+ diffusion, accommodate the volume variation, and inhibit the aggregation and pulverization of the electrode. We believe that the current work can provide a new strategy for designing and fabricating high-performance anode materials for LIBs.

U/Th and 14C Crossdating of Parietal Calcite Deposits: Application to Nerja Cave (Andalusia, Spain) and Future Perspectives

Abstract14C and U/Th methods were used to date three thin carbonate layers deposited on decorated walls of Nerja Cave (Malaga, southern Spain) in order to constrain the age of the parietal non-figurative marks situated under these carbonate layers. Modern formations were also dated to estimate the detritic contribution for the U/Th method and the dead carbon proportion for 14C dating. We sampled two locations with ocher painting marks. In one case (mark 1), the good agreement between the ages obtained by the two methods suggests that the sample was not subjected to post-deposition alteration and that the results are reliable. In the other case (mark 2), the age discrepancy between the two methods reached 30,000 yr, indicating that geochemical alteration had affected the sample and that one or both results were inaccurate. The ages for mark 1 indicate that this type of non-figurative representation is older than 25,000 cal BP and that it can be associated with the oldest attested Paleolithic occupation of Nerja Cave.

Designing of stable and highly efficient ordered Pt2CoNi ternary alloy electrocatalyst: The origin of dioxygen reduction activity

We report an ordered Pt2CoNi ternary alloy nanoelectrocatalyst, synthesized via simple molten salt synthesis (MSS) procedure and also defined theoretically a new descriptor to explain the origin of exceptional oxygen reduction reaction (ORR) activity. The catalyst consists of a very thin layer of carbon, since the seed-growth of such ordered Pt2CoNi nanoelectrocatalyst has been originated through the pores of high surface area carbon during a MSS. Electrocatalytic ORR activity of Pt2CoNi nanoelectrocatalyst is 5–6 times higher than that of commercial Pt/C catalyst with fascinating stability behavior in acidic media. Most interesting behavior of this Pt2CoNi has been observed after 15,000 and 25,000 durability cycles, where 16 times activity enhancement is achieved at 0.9V. Furthermore, after 25,000 cycles, a specific activity of 0.605mA/cm2Pt (22 times higher than its own) has been observed at 1.0V for the first time. Density functional theory (DFT) based calculation is used to estimate the onset potential by plotting the free energy profile for ORR of each active site of nanocatalyst. New descriptors are proposed to explain the origin of exceptional catalytic activity of ternary metal nanoelectrocatalyst.

Carbon Molecular Sieve Membranes from Polyetherimide: Effect of Pyrolysis Temperature on O2/N2 Selectivity

Carbon molecular sieve (CMS) membranes with excellent separation performance and stability appear to be promising candidate for gas separation. In this work, CMS membranes were formed by a thin carbon layer obtained by pyrolysis of a coated polyetherimide solution onto porous disk support. The pyrolysis temperatures were varied under inert condition. Results showed that the pyrolysis temperature played an important role in determining the gas permeability of CMS membranes. The CMS membrane prepared at pyrolysis temperature of 700°C shows high surface area and narrow PSD with well developed microporous carbon structures. The development of large pore occurs at higher pyrolysis temperature. The O2/N2 permselectivities of 2.86, 2.61 and 2.22, respectively were attained by CMS membranes prepared at pyrolyzed temperature of 700, 800 and 900°C.

Facile hydrothermal synthesis of carbon-coated cobalt ferrite spherical nanoparticles as a potential negative electrode for flexible supercapattery

Battery type electrodes would replace the currently available pseudocapacitive electrodes by the cause of high energy density and long discharge time. In this regard, battery type carbon coated CoFe2O4 spherical nanoparticles is prepared by the facile hydrothermal method and tested as the possible negative electrode for supercapattery applications. The phase purity, electronic states of elements, and the presence of carbon is inferred through various sophisticated techniques. The calculated surface area of CoFe2O4 and carbon coated CoFe2O4 are found to be 9 and 26 m2 g−1, respectively. The morphological analysis confirms the formation of uniform CoFe2O4 nanospheres (∼25 nm) with a thin layer of carbon coating (∼2 nm). The amorphous carbon coating over CoFe2O4 nanosphere is identified via high-resolution transmission electron microscope. The observed peak and plateau regions in the cyclic voltammogram and galvanostatic charge/discharge curves reveals the battery-type charge storage behaviour of the material. The carbon coated CoFe2O4 delivers the maximum length capacitance of 9.9 F m−1 at 1 mV s−1 with a useful lifespan over 5000 cycles. The electrochemical impedance spectroscopy reveals that the carbon-coated CoFe2O4 delivers the low charge transfer resistance than CoFe2O4. Further, the fabricated supercapattery provides the energy density of 160 × 10−8 Wh cm−1 at a power density of 67.2 μW cm−1. As well as, the device shows 93% of coulombic efficiency and 75% of the specific capacitance retention over 11,000 cycles. Overall, it is believed that the carbon-coated CoFe2O4 can serve as a good candidate for flexible supercapatteries.

Constructing Ultrahigh-Capacity Zinc–Nickel–Cobalt Oxide@Ni(OH)2 Core–Shell Nanowire Arrays for High-Performance Coaxial Fiber-Shaped Asymmetric Supercapacitors

Increased efforts have recently been devoted to developing high-energy-density flexible supercapacitors for their practical applications in portable and wearable electronics. Although high operating voltages have been achieved in fiber-shaped asymmetric supercapacitors (FASCs), low specific capacitance still restricts the further enhancement of their energy density. This article specifies a facile and cost-effective method to directly grow three-dimensionally well-aligned zinc-nickel-cobalt oxide (ZNCO)@Ni(OH)2 nanowire arrays (NWAs) on a carbon nanotube fiber (CNTF) with an ultrahigh specific capacitance of 2847.5 F/cm3 (10.678 F/cm2) at a current density of 1 mA/cm2, These levels are approximately five times higher than those of ZNCO NWAs/CNTF electrodes (2.10 F/cm2) and four times higher than Ni(OH)2/CNTF electrodes (2.55 F/cm2). Benefiting from their unique features, we successfully fabricated a prototype coaxial FASC (CFASC) with a maximum operating voltage of 1.6 V, which was assembled by adopting ZNCO@Ni(OH)2 NWAs/CNTF as the core electrode and a thin layer of carbon coated vanadium nitride (VN@C) NWAs on a carbon nanotube strip (CNTS) as the outer electrode with KOH poly(vinyl alcohol) (PVA) as the gel electrolyte. A high specific capacitance of 94.67 F/cm3 (573.75 mF/cm2) and an exceptional energy density of 33.66 mWh/cm3 (204.02 μWh/cm2) were achieved for our CFASC device, which represent the highest levels of fiber-shaped supercapacitors to date. More importantly, the fiber-shaped ZnO-based photodetector is powered by the integrated CFASC, and it demonstrates excellent sensitivity in detecting UV light. Thus, this work paves the way to the construction of ultrahigh-capacity electrode materials for next-generation wearable energy-storage devices.

Ni3N@Ni-Ci nanoarray as a highly active and durable non-noble-metal electrocatalyst for water oxidation at near-neutral pH

It is of great importance to design and exploit high-efficiency low-cost electrocatalysts for the oxygen evolution reaction (OER) under mild conditions for applications. In this Article, we propose that formation of a thin amorphous Ni carbonate layer on Ni3N nanoarray supported on carbon cloth (Ni3N NA/CC) is an effective strategy to boost its OER activity in at near-neutral pH. When used as a 3D non-noble-metal OER electrocatalyst, the resulting core–shell Ni3N@Ni-Ci NA/CC displays superior catalytic activity with extremely small overpotential of 400 mV for 20 mA cm−2 in 1.0 M KHCO3 (bulk pH: 8.3). Moreover, it also exhibits considerable long-term electrochemical durability with its activity being preserved for at least 12 h. Conductive Ni3N nanoarray not only provides as the Ni source for in-situ electrochemical derivation of 3D Ni-Ci catalyst with high surface area, more exposed active sites and facilitated mass diffusion, but effectively prompts the electron transport from Ni-Ci shell to CC, enabling more efficient water oxidation electrocatalysis.

Spray-drying assisted synthesis of a Li4Ti5O12/C composite for high rate performance lithium ion batteries

Spinel crystalline lithium titanium oxide (Li4Ti5O12 or LTO) has gained attention as a possible alternative material to graphite for use as anodes in lithium-ion rechargeable batteries due to its low volume expansion and dendrite-free long-term stability. However, the rate capability of LTO is limited by its low electronic conductivity, which results in a large polarization resistance between electrodes. In this study, we demonstrate a spray-drying-assisted carbon coating approach to synthesize LTO/C composites for enhanced lithium-insertion capacity and facilitated charge-discharge reaction kinetics. The thin carbon layer of LTO/C composite contributes to suppressing particle growth by forming passivating carbon layers. In addition to the decrease in particle size for short lithium-diffusion pathways, the highly conductive carbon layers reduce the interfacial resistance between the electrode and electrolyte by enhanced electrical conductivity. The electrochemical performances of the spray-drying-prepared LTO/C composite such as the specific capacity, cycle and rate capabilities, and impedance are compared with pristine LTO and carbon-coated LTO synthesized without spray-drying. The LTO/C prepared from glucose exhibits a 11.15% enhancement in rate characteristics of pristine LTO at 0.5C after 100 cycles. These results indicate that the carbon coating layer promotes charge transfer and ion diffusion as well as provides a buffering effect for improved rate and cyclic capabilities.