Nanostructured Carbon Materials Research Articles

Graphene Aerogels: Structure Control, Thermal Characterization and Thermal Transport

Graphene aerogel (GA) as one of the innovative carbon nanostructured materials is superior with flexibility, strong mechanical strength, lightweight, high porosity and excellent durability, which attracted wide research interests and fulfill the requirements for various novel applications in energy conversion and storage, sensor, thermal management, and environment areas, etc. The thermal property among other important properties of GA is important for its novel applications. In this work, we first introduce the synthesis and microstructure control method for GA, including pore size control, anisotropic pore structure control, and heterostructure control. The methods for measuring the thermal conductivity of bulk GAs in air (apparent k) and the k of solid matrix of GAs are introduced in detail, respectively. Finally, we review the thermal transport models for GAs, including the air–solid coupling models, models for calculating the intrinsic thermal properties of graphene nanoflakes, as well as the thermal reffusivity model and dominating thermal contact resistance model. Challenges and opportunities in the study of thermal transport in 3D GAs are discussed. Considering the remarkable complexity of physical/chemical structure of GAs, there is still a large room in understanding fundamentals of energy transport in these three-dimensional graphene networks, which will pave the way toward their novel applications in the near future.

Application of Carbon Nanotube-Based Materials as Interlayers in High-Performance Lithium-Sulfur Batteries: A Review

With the ever-increasing demands of electrochemical energy storage, lithium–sulfur (Li–S) batteries have drawn more attention because of their superior theoretical energy density and high specific capacity. However, practical applications of Li–S batteries suffer from problems such as low conductivity of sulfur and discharged products, severe polysulfide shuttling effect, and large volume change of sulfur during cycling, resulting in sluggish rate performance, and unsatisfactory cycle life. Various nanostructured carbon materials have been served as barrier layers to overcome these problems. In particular, carbon nanotubes (CNTs) with unique 1D nanostructure, have been introduced to Li–S batteries as the intermediate layers because of its superior flexibility, excellent electrical conductivity, and good chemical stability. Moreover, CNTs and CNTs-based barrier layers could also curb lithium polysulfides shuttling. In the minireview, we summarize recent works of CNTs-based materials as modifying interlayers for Li-S batteries. In addition, the strategies to enhance electrochemical performances of the batteries are summarized and discussed. Finally, the challenges and prospects for future research of CNTs-based materials as interlayer are proposed. We hope this review will be useful for designing and fabricating high-performance Li–S batteries and boost their practical applications.

Brief review on thin films, perovskite solar cells and nanostructure’s applications

In this brief review, we studied the development milestones of thin film photovoltaics (PV) made of CdTe, CIGS, CZTS and perovskite materials and expanded the discussion to the application of graphene and nanotube in the architecture of these devices. Thin film solar cells are alternative for Si-based PVs and reached a comparable performance to Si PVs. However, they mostly suffer from instability in device and performance and thus several research groups considered the application of graphene and nanostructure carbon materials as conductive electrodes of such devices. The stability of such devices has been the main barrier on up-scaling the cell to module level despite the performance being beaten 23% so far. For emerging perovskite solar cells, the main approach of the researchers is to protect the perovskite layer from moisture and humidity degradation by bringing the protective layers such as graphene and nanotubes or carbon deviations into the devices structure. It has been revealed that graphene’s excellent heat dissipation and thermal conductivity can reduce the moisture reaction with perovskite layer which promises device stability at air.

Experimental characterization of three-dimensional Graphene’s thermoacoustic response and its theoretical modelling

In the past decade, a lot of research has been conducted on the potential of carbon nanostructured materials to emit sound via thermoacoustics through both simulations and experiments. However, experimental validation of simulations for three-dimensional graphene (3D-C), which has a complicated 3D structure, has yet to be achieved. In this paper, 3D-C is synthesized via thermal chemical vapor deposition and its microstructure and quality tested using Scanning Electron Microscopy and Raman spectroscopy respectively. Then, a two temperature model is used to predict the effects of numerous parameters: frequency, input power, sample size, connection area, connection path, pores per inch, thickness, compression as well as the addition of a backing on the acoustic performance and temperature of the sample. The experimental results presented in this paper validate the predictions of the adopted two temperature model. The efficiency of 3D-C is then compared with results presented in other studies to understand how the presented 3D-C fared against ones from the literature as well as other carbon nanostructured materials.

Thermal Degradation of Nafion in the Presence of Nanostructured Materials: Thermally Expanded Graphite, Carbon Black, and Platinum

Thermal degradation in air of Nafion proton-conducting polymer in composites containing nanostructured carbon materials [carbon black of Vulcan XC-72 grade and a graphene-like material (thermally expanded graphite)] and platinum nanoparticles was studied by nonisothermal kinetic analysis. The effect of the contact of Nafion with one or another material of the composite on the degradation kinetics was examined. The activation energy of Nafion desulfonation was calculated in relation to the component composition. The temperature dependence of the polymer lifetime for materials of different component compositions was evaluated. The materials were characterized by scanning and transmission electron microscopy and by differential thermal analysis. The presence of carbon materials enhances the heat resistance of Nafion and narrows the temperature interval of its degradation. The presence of various forms of carbon material (carbon black, thermally expanded graphite) and of platinum nanoparticles influences the Nafion desulfonation and its kinetic characteristics differently. The mechanism of thermal stabilization of Nafion in the presence of carbon materials was suggested.

The effect of synthesis temperature on the carbon yield and characteristics of nano composite C-CNFs

Synthesis temperature is one of important factors influencing on characteristics of carbon nanostructured materials. In this article, the authors evaluate the change of properties of nano composite C-CNFs obtained by simultaneously synthesizing and decorating NFs on the surface of the carbon felt at different temperatures. The results have shown that the carbon yield increases from 5.55 %wt to 227.13 %wt by enhancing the growth temperature from 620 oC to 680 oC. The results from Raman spectrum analysis have indicated that when the temperature rises from 620 oC to 680 oC, the ID/IG ratio decreases from 0.932 to 0.728. The decrease of ID/IG ratio has affirmed the increase in the graphitization degree of the product. However, this ratio increases slightly to 0.749 when the temperature is at 710 oC. This result demonstrate formation of amorphous carbon at high temperature. Besides, the obtained C-CNFs are also analyzed by several techniques such as SEM, TEM, TGA and BET.

Dicyandiamide-formaldehyde and Borassus Flabellifer inflorescence assisted preparation of low surface area nitrogen-doped carbon as high-performance anode for lithium-ion batteries

The heteroatom-doped disordered and nanostructured carbon materials have gained significant attention due to their enormous potential to improve the performance of energy applications. In this context, we have successfully developed a sustainable green synthesis of disordered and nanostructured nitrogen-doped carbon using pre-carbonized Borassus Flabellifer Male Inflorescence biomass coated with Dicyandiamide and Formaldehyde polymer, which subsequently subjected to thermal activation at 1000 °C for 6 hrs in nitrogen environment and it has lower surface area (30.76 m2 g−1). The prepared N-doped carbon, when used as an anode in Li-ion batteries, delivered an outstanding reversible specific capacity of 655.8 mAh g−1 at a current density of 100 mA g−1 with the stable cycling behaviour for 1500 cycles. Even at a higher current rate (1000 mA g−1), the prepared carbon displayed a reversible capacity of 351.9 mAh g−1, thus making it a promising anode candidate for the next generation of high power lithium-ion batteries (LIBs).

Atomic-Distributed Coordination State of Metal-Phenolic Compounds Enabled Low Temperature Graphitization for High-Performance Multioriented Graphite Anode.

Continuous efforts have been made to achieve nanostructured carbon materials with highly ordered graphitic structures using facile synthetic methods. 3D graphite nanoballs (GNBs) are synthesized by the low-temperature pyrolysis of a non-graphitizable precursor, tannic acid (TA). Abundant phenol groups on TA bind to Ni2+ to form metal-phenolic coordination, which renders each Ni cation to be atomically distributed by the TA ligands. Even at low temperatures (1000 °C), highly ordered graphitic structure is promoted by the distributed Ni nanoparticles that act as a graphitization catalyzer. The crystallinity of the GNB is fully corroborated by the intense 2D peak observed in Raman spectroscopy. In particular, the graphitic layers have orientations pointing toward multidirections, which are beneficial for the rapid transport of Li-ions into graphite grains. The resulting materials exhibit outstanding electrochemical performance (120 mAh g-1 at 5 C and 282 mAh g-1 at 0.5 C after 500 cycles) when evaluated as a fast-chargeable negative electrode for lithium ion batteries.

Hierarchical polypyrrole/graphene/melamine composite foam for highly compressible all-solid-state supercapacitors

Nanostructured carbon materials have shown promising applications for energy storage because of their high capacitive characteristic. However, developing three-dimensional (3D) hierarchical carbon materials with both high compressibility and capacitance is still challenging. Herein, we report the fabrication of hierarchical polypyrrole (PPy)/graphene (reduced graphene oxide (G) and holey reduced graphene oxide (h-G))/melamine composite foam through a simple template method. By systematically optimizing the mass ratios of the G/h-G and the sizes of the PPy nanoparticles (PPy NPs), the as-prepared composite electrode displays a gravimetric capacitance of 422.6 F g−1 at a current density of 0.5 A g−1. Due to the interconnected h-G/G network and elastic melamine foam (MF) skeleton, the as-prepared composite electrode also shows compressible performance, which can be compressed to a strain of 60% and completely recover to its original shape when released. When the composite electrodes are assembled to a compressible supercapacitor which shows a stable capacitance under different compressive strains (0%, 25%, 50% and 75%) and a long-term compression test at 50% strain for 100 cycles. Therefore, the successful preparation of compressible composite electrode should open many opportunities in compressible and durable energy storage devices.

Selective laser melting of low-content graphene nanoplatelets reinforced 316L austenitic stainless steel matrix: Strength enhancement without affecting ductility

Metal matrix composites reinforced by carbon nanostructured material are beneficial in achieving a balance between strength and ductility. However, achieving this balance in stainless steel through the selective laser melting (SLM) process remains a challenge. In this study, SLM is used to fabricate 316 L stainless steel matrix composites, which are reinforced with 0.1 wt.% single-layer graphene nanoplatelets (GNPs). The optimal process parameters are obtained by combining the analyses of the relative density and mechanical properties. The results show that the GNPs in the 316 L/GNPs composites are dispersed at the grain boundary, either parallel or at a certain angle to the grain boundary. Based on the tensile test, the ultimate tensile strength of the 316 L/GNPs composites is 738 MPa, which was 17.9 % higher than that of 316 L. Furthermore, both SLM-printed 316 L and 316 L/GNPs composites have an elongation of ∼38 %. The interaction between the GNPs and the molten pool, and the redistribution of the GNPs leads to the formation of a lamellar and relatively high-density distribution area of GNPs in the molten pool. The strengthening mechanism of 316 L/GNPs composites is also elucidated. These results provide insights into enhancing the combined strength-ductility property of other SLM-printed GNPs reinforced metal matrix systems.

Effect of an activating agent on the physicochemical properties and supercapacitor performance of naturally nitrogen-enriched carbon derived from Albizia procera leaves

The present study reports the preparation of naturally nitrogen-doped carbon nanostructured materials from Albizia procera leaves with enhanced electrochemical supercapacitance properties. The doped carbon materials were prepared by the pyrolysis of Albizia procera leaves at 850 °C. The effect of using various activating agents such as NaHCO3 and ZnCl2 was checked and compared on the structural and textural properties, specific capacitance, surface functional groups, and surface area. The Brunauer–Emmett–Teller(BET) analysis shows that NaHCO3-activated nitrogen-doped carbon (NaNC) has a higher specific surface area compare to ZnCl2-activated nitrogen-doped carbon (ZnNC) and nitrogen-doped carbon prepared without an activating agent (WANC). Overall, the BET and microscopic analyses confirmed that NaNC is composed of carbon nanosheets with macropores and mesopores, as well as a large number of micropores, which is completely different from the composition of ZnNC and WANC. In addition, the XPS analysis confirmed the existence of higher amount of nitrogen in NaNC compared to that of ZnNC, and WANC. NaNC exhibits a specific capacitance of 231 F g−1 at 1 A g−1 current with good energy and power densities, and an outstanding charging-discharging stability thanks to its unique features such as the existence of high amounts of nitrogen, high SSA, and the nanosheet-type morphology.

Electrodeposition of Metal Oxides on Spray-Coated Nanostructured Carbon Framework As High Performance Electrode Materials for Asymmetric Pseudocapacitors

Combining transition metal oxides and nanostructured hierarchical carbon materials is considered as one of the best strategy to achieve high performance supercapacitors electrodes [1]. Here is reported a novel way to increase energy densities while maintaining high power densities exploiting pseudocapacitance and nanostructuration of electrode materials.In the first part of this study, carbon nanotubes/graphene/manganese dioxide nanostructured films were designed as pseudocapacitors electrodes (Fig. A). While MnO2 is a well-known pseudocapacitive cathode material and will increase energy densities [2], nanostructured carbon materials provide high electronic conductivity and specific surface. The challenge is to assemble these three materials (CNTs/G/MnO2) into a nanostructured electrode with controlled homogeneity, morphology, and composition. First, carbon nanotubes and graphene foils are associated in a specific multi-layered organization onto a current collector by dynamic spray gun deposition. It creates a controlled porous network in the electrodes. This deposition method used for nanostructuration of thin films generates homogeneous mats with tunable thickness. This structuration of the carbon nanomaterials is reproducible, easily scalable and low-cost considering that it is compatible with large surfaces. The CNTs/G multilayered structure provides a good accessibility with an appropriate porosity for ion insertion (pores of 2 to 6 nm), a high specific surface area (~360 m2/g), and an electrically conductive network (~3600 S/m), all necessary to confer high power densities. Our approach consists in synthesizing MnO2 by anodic electrodeposition directly onto the conductive nanostructured carbon framework. Electrodeposition is very versatile [3] and simply. The morphology of the manganese dioxide (shape, particles size, and mass loading) can be controlled and the electrochemical performances can be tuned by adjusting the deposition conditions. The MnO2 nanoparticles are deposited through the thickness (seen in cross section Figure A) of the carbon mat with controlled sizes ranging from 50 to 200 nm.Materials are characterized by SEM, XPS, microporosity analysis and electrochemistry. Results demonstrate that the capacitance can reach up to 220 F/g for binder free electrodes with a MnO2 mass loading of 55%. The pseudocapacitive oxide insures a faradaic contribution that enhances the specific capacitance by a factor 5 compared to the carbon nanomaterials structure only. The electrodes present an outstanding stability of 96% over 3 000 cycles in aqueous electrolytes (Na2SO4 1M). Then an asymmetric system with activated carbon as the negative electrode is developed to demonstrate the energy density increase compared to a symmetric system with activated carbon as electrodes. When adding MnO2 to the cathode the exploitable potential window can be widen up to 1.4V and the energy density increases from 1 Wh/kg to 6 Wh/kg for a power density of 0.7 kW/kg. Stability of 85% in capacitance was demonstrated for 20 000 cycles on this system.The second part of the contribution is devoted to molybdenum oxide (MoO3) that has been recently introduced as an appropriate anode material for pseudocapacitors in view of its low cost nature and high electrochemical activity [4,5]. It has been reported to be suitable in terms of potential window as a negative counterpart to manganese oxide in asymmetric pseudocapacitors [6]. This study focuses on the development of a carbon nanotubes/molybdenum oxide composite by spray-coating and cathodic electrodeposition (Fig. B). The growth of this specific metal oxide is quite complex with several possible intermediaries presenting different oxidation states depending on the environment [7]. Studies on the impact of the chemical and electrochemical conditions on the morphology, crystallinity, and homogeneity of the oxide layer are performed and thermal treatments aiming to enhance these parameters and stabilize the electrochemical performances are explored. Solubility of the deposited MoOx has been found to be a major issue in aqueous electrolytes and in that regard tests have been performed in organic electrolytes with lithium salts to insure stability of the final system. First results obtained for a simple binary MoOx-CNTs electrode already present a good maximum specific capacitance of 110 F/g. [1] National Science Review, 4, 1 (2017) 71–90 [2] Prog. Mater. Sci. 74 (2015) 51-124. [3] Ceram. Int. 44 (2018) 10863-10870. [4] Chem. Commun., 2011, 47, 10058–10060 5] Materials Letters 66 (2012) 102–105 [6] Adv. Funct. Mater. 2013, 23, 5074–5083 [7] Analytica Chimica Acta 496 (2003) 39–51 Figure 1

In-situ growth of novel CNTs-graphene hybrid structure on Ni-silica nanocomposites by CVD method for oxygen evolution reaction

Carbon nanostructures are ideal materials for electrochemical reactions like oxygen evolution reaction (OER) due to excellent electrical conductivity, resistance to strong acidic as well as basic conditions and conductive support material for transition metals. In this work we have synthesized multiwalled carbon nanotubes MWCNTs along with graphene growth in-situ by CVD method at 650 °C on nickel-silica nanocomposites for OER in alkaline medium. After removal of silica, our material exhibited comparable OER performance with that of commercial Iridium supported carbon i.e. Ir/C (20 wt % Ir) electrocatalyst. The OER performance is attributed to the defective nature of MWCNTs in the form of surface discontinuities found on rolled graphene layers of carbon nanotubes along with MWCNTs-graphene interfaces which presumably contain dangling bonds as active sites for OER. The overpotential at current density of 10 mA/cm2 exhibited by MWCNTs-graphene hybrid carbon nanostructured material was 310 mV in 1 M KOH solution at scan rate of 5 mV/s while commercial Ir/C material revealed overpotential of 305 mV under similar conditions.

Nanostructured Carbon Material Effect on the Synthesis of Carbon-Supported Molybdenum Carbide Catalysts for Guaiacol Hydrodeoxygenation

The impact of using different nanostructured carbon materials (carbon nanofibers, carbon nanotubes, graphene oxide and activated carbon) as a support for Mo2C-based catalysts on the hydrodeoxygenation (HDO) of guaiacol was studied. To optimise the catalyst preparation by carbothermal hydrogen reduction (CHR), a thermogravimetric study was conducted to select the optimum CHR temperature for each carbon material, considering both the crystal size of the resulting β-Mo2C particles and the extent of the support gasification. Subsequently, catalysts were prepared in a fixed bed reactor at the optimum temperature. Catalyst characterization evidenced the differences in the catalyst morphology as compared to those prepared in the thermogravimetric study. The HDO results demonstrated that the carbon nanofiber-based catalyst was the one with the best catalytic performance. This behaviour was attributed to the high thermal stability of this support, which prevented its gasification and promoted a good evolution of the crystal size of Mo species. This catalyst exhibited well-dispersed β-Mo2C nanoparticles of ca. 11 nm. On the contrary, the other supports suffered from severe gasification (60–70% wt. loss), which resulted in poorer HDO efficiency catalysts regardless of the β-Mo2C crystal size. This exhibited the importance of the carbon support stability in Mo2C-based catalysts prepared by CHR.

Synthesis of Multilayer Graphene Oxide in Electrochemical Graphite Dispersion in H2SO4

The possibility of electrochemical dispersion of natural graphite powder in 83% H2SO4 was studied to produce multilayer graphene oxide. It has been shown that the decisive effect on the exfoliation of graphite particles is exerted by the processes of intercalation of graphite and the release of gaseous oxygen. It has been established that coarse-grained graphite powders with a particle size exceeding 200 Μm are more susceptible to electrochemical dispersion. The resulting carbon nanostructured materials tend to agglomerate in an aqueous dispersion. During sonication, the particle size of oxidized graphite decreases markedly with the formation of multilayer graphene oxide.

Pt-Ni@PC900 Hybrid Derived from Layered-Structure Cd-MOF for Fuel Cell ORR Activity

Fuel cell technology is the supreme alternate option for the replacement of fossil fuel in the current era. Pt alloys can perform well as fuel cell electrodes for being used as catalytic materials to perform the very notorious oxygen reduction reaction. In this regard, first, a layered metal–organic framework with empirical formula [C8H10CdO7]n·4H2O is synthesized and characterized using various experimental and theoretical techniques. Then, a nanostructured porous carbon material with a sheet morphology (PC900) having a high BET surface area of 877 m2 g–1 is fabricated by an inert-atmosphere thermal treatment of the framework upon heating up to 900 °C. Pt and Ni nanoparticles are embedded into PC900 to prepare a homogenized hybrid functional material, i.e., Pt-Ni@PC900. The Pt-Ni@PC900 hybrid is proved to be an excellent ORR catalyst in terms of half-wave potential and limiting current density with 7% Pt loading compared with the commercially available 20% Pt/C catalyst. Pt-Ni@PC900 also shows stability of current up to 12 h with only a very small variation in current. This work highlights the importance of Pt alloys in future large-scale commercial applications of fuel cells.

Houttuynia-derived nitrogen-doped hierarchically porous carbon for high-performance supercapacitor

Three-dimensional (3D) heteroatom-doped nanostructured carbon materials have gained extensive attention because of their tremendous potential for enhancing supercapacitor performance. Herein, based on a mild carbonization/activation process we successfully developed green/sustainable 3D hierarchically porous nitrogen-doped nanostructure carbon (N–HNC) materials from houttuynia biomass, showing high specific capacitance and high cyclic stability. The as-prepared houttuynia-derived porous carbon material shows a unique flower-like architecture with well-distributed micro/meso pores and a high specific surface area of 2090 m2/g. The assembled supercapacitor based on N–HNC sample shows superior specific capacitance (473.5 F/g at 1 A/g) and remains over 50% of specific capacitance at 20 A/g. The N–HNC based symmetric supercapacitor, constructed with a two-electrode configuration, shows an energy density of 15.99 Wh/kg at 500 W/kg and outstanding capacitance retention of 95.74% even after 10,000 charge-discharge cycles at 10 A/g in an aqueous 6 M KOH electrolyte system. The results highlight the potential of the 3D porous N-doped hierarchical nano-structural carbon materials from houttuynia biomass as candidate electrodes for supercapacitor applications. This study provides an example of using the inherent framework structure of biomass as a precursor to synthesize hierarchically porous nitrogen-doped nanostructure for high-performance supercapacitor applications.

Designing a slope-dominated hybrid nanostructure hard carbon anode for high-safety and high-capacity Na-ion batteries

A slope-dominated mechanism is designed by preparing hybrid nanostructure carbon materials using a CVD-like method which provides hard carbon with excellent rate performances and high average discharge potential as an anode for Na-ion batteries.

Recent advances in nanostructured carbon for sodium-ion batteries

The review elaborates on diversified nanostructured carbon materials and their modifications from two different perspectives of dimensions and graphitization degree.

N-doped 3D porous carbon materials derived from hierarchical porous IRMOF-3 using a citric acid modulator: fabrication and application in lithium ion batteries as anode materials.

N-doped three-dimensional carbon nanostructured materials were obtained by calcinating hierarchical porous IRMOF-3 materials, and were fabricated in the presence of citric acid as a modulator via the conventional synthetic protocol, at 900 °C in an Ar atmosphere. The resultant carbon materials were used as anode materials for lithium ion batteries, and exhibited excellent lithium storage capacity and cycling stability and maintained a capacity of about 555 mA h g-1 at the current density of 0.2 A g-1 after 100 cycles.