Graphitization Process Research Articles

A comparative appraisal of Raman band ratioing and chemometric analysis for classification of ancient papyri

Papyri from past civilizations represent key information sources to understand historical societies and their culture. In general, the most critical information usually derives from the inks rather than the supports. In this work, we combine several analytical tools, including vibrational spectroscopies (FT-IR and Raman) and SEM/EDX spectroscopy, to characterise the inks of various papyri in the Palau-Ribes collection (Barcelona, Spain). The Raman spectra corroborate the presence of soot-based inks as the primary type. We use a five-peak spectral model for the deconvolution of the first-order region of the Raman spectra, which allows us to derive information about the carbon type of the soot-based inks. Further, we propose various Raman band ratios for a thorough evaluation of the graphitization process of carbon and possible classification of the ancient inks. At the same time, we use multivariate analysis, mainly assisted by cluster analysis, principal component analysis, and the Fisher discriminant functions, to enable an excellent alternative way to verify the classification and differentiation of the inks safely as a function of the historical time.

Microwave-Assisted Coal-Derived Few-Layer Graphene as an Anode Material for Lithium-Ion Batteries.

A few-layer graphene (FLG) composite material was synthesized using a rich reservoir and low-cost coal under the microwave-assisted catalytic graphitization process. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to evaluate the properties of the FLG sample. A well-developed microstructure and higher graphitization degree were achieved under microwave heating at 1300 °C using the S5% dual (Fe-Ni) catalyst for 20 min. In addition, the synthesized FLG sample encompassed the Raman spectrum 2D band at 2700 cm−1, which showed the existence of a few-layer graphene structure. The high-resolution TEM (transmission electron microscopy) image investigation of the S5% Fe-Ni sample confirmed that the fabricated FLG material consisted of two to seven graphitic layers, promoting the fast lithium-ion diffusion into the inner surface. The S5% Fe-Ni composite material delivered a high reversible capacity of 287.91 mAhg−1 at 0.1 C with a higher Coulombic efficiency of 99.9%. In contrast, the single catalyst of S10% Fe contained a reversible capacity of 260.13 mAhg−1 at 0.1 C with 97.96% Coulombic efficiency. Furthermore, the dual catalyst-loaded FLG sample demonstrated a high capacity—up to 95% of the initial reversible capacity retention—after 100 cycles. This study revealed the potential feasibility of producing FLG materials from bituminous coal used in a broad range as anode materials for lithium-ion batteries (LIBs).

Effect of Temperature and Acoustic Pressure During Ultrasound Liquid-Phase Processing of Graphite in Water

Ultrasound-assisted liquid-phase exfoliation is a promising method for manufacturing two-dimensional materials. Understanding the effect of ultrasonication parameters such as the temperature and input power on the developed pressure field is pivotal for optimization of the process. Limited research has been carried out to determine the optimal temperature for exfoliation, with some data generating disputed results. Simply maximizing the sonication power does not necessarily produce a higher yield because of shielding. In this study, a high-temperature calibrated cavitometer was used to measure the acoustic pressure generated in different graphite solutions in deionized water at various temperatures (from 10°C to 70°C) and input power conditions (from 20% to 100%). In addition, high-speed optical imaging provided insight on the shock wave generation from transient bubble collapses under different sonication conditions. The optimal sono-exfoliation parameters were determined to be 20% input power at 10°C for graphite flake solution, and 100% input power at 40°C to 50°C for graphite powder solution.

Effect of initial microstructure on graphitization behavior of Fe–0.55C–2.3Si steel

In this study, the effect of the initial microstructure (i.e., ferrite + pearlite or martensite) on the graphitization behavior and microstructural evolution during heat treatment of a hot-rolled medium-carbon, high-silicon steel (Fe–0.55C–2.3Si) is investigated. When a sample consists of ferrite and pearlite, its microstructure gradually changes to ferrite and graphite during heat treatment via the decomposition of pearlite and the formation of graphite particles. In the sample with a martensite microstructure, the phase transformation occurs in the following step: martensite → ferrite + cementite → ferrite + graphite. Although the graphitization process of the martensite sample is more complex than that of the ferrite + pearlite sample, the graphitization rate is substantially faster in the former owing to more abundant grain boundaries and triple junctions that act as nucleation sites for graphite. When the initial microstructure changes from ferrite + pearlite to martensite, the graphite completion time significantly reduces from 16 to 2 h at 650 °C and from 6 to 0.5 h at 700 °C. After complete graphitization, the average size and number density of graphites in the martensite sample are respectively smaller and higher than those in the ferrite + pearlite sample. The rate of hardness decrease (i.e., material softening) during heat treatment is also faster in the martensite sample. These results demonstrate that changing the initial microstructure from ferrite + pearlite to martensite is an effective means to accelerate the graphitization behavior and acquire a graphitized steel with uniformly distributed fine graphite particles.

3D Structured Graphene Anodes for Alkali Metal Ion Storage Applications

Electrochemical exfoliation of graphite into graphene has emerged as a promising manufacturing method for the fast production of graphene at a low cost. We will first discuss our recent efforts to understand the electrochemical exfoliation process of graphite under various electrolyte conditions to control the structures of graphene products.1 Then, we will introduce the stacking and defect engineering processes to assemble 3D structured graphene electrodes.2, 3 The 3D graphene anodes delivered enhanced capacities for Li-, Na-, K-ion storage due to the effective utilization of surface defects. In particular, the 3D graphene anodes can exhibit superior charge-storage performance under extremely low-temperature conditions. We reveal that the role of the surface-charge storage mechanism in improving the charge storage performance under low-temperature conditions.References Lee, H.; Choi, J. I.; Park, J.; Jang, S. S.; Lee, S. W. Role of anions on electrochemical exfoliation of graphite into graphene in aqueous acids. Carbon 2020, 167, 816-825.Lee, B.; Kim, M.; Kim, S.; Nanda, J.; Kwon, S. J.; Jang, H. D.; Mitlin, D.; Lee, S. W. High Capacity Adsorption—Dominated Potassium and Sodium Ion Storage in Activated Crumpled Graphene. Adv. Energy Mater. 2020, 10, 1903280.Lee, M. J.; Lee, K.; Lim, J.; Li, M.; Noda, S.; Kwon, S. J.; DeMattia, B.; Lee, B.; Lee, S. W. Outstanding Low-Temperature Performance of Structure-Controlled Graphene Anode Based on Surface-Controlled Charge Storage Mechanism. Adv. Funct. Mater. 2021, 31, 2009397.

Fluctuations in Graphitization of Coal Seam-Derived Natural Graphite upon Approaching the Qitianling Granite Intrusion, Hunan, China

The Lutang graphite deposit in Chenzhou, Hunan province, China, is a well-known coal seam-derived graphite (graphite formed from coal during its natural evolution) deposit with proven reserves of 9.5 million tons and prospective reserves of around 20 million tons (2015 data). The graphite occurs at an andalusite bearing sericite quartz chlorite metamorphic mudstone around a c. 530 km2 Qitianling granite intrusion. A set of coal seam-derived graphite samples from the Lutang graphite deposit in Hunan was examined by geochemical, crystallographic, and spectroscopic techniques to assess changes in the degree of graphitization approaching the intrusion. The carbon content, degree of graphitization, and Raman spectral parameters of series coal seam-derived natural graphite samples show a fluctuating increase with increasing proximity to the granite intrusion. The profile of geological structural features has a close spatial correlation with the variations in the degree of graphitization of series coal seam-derived natural graphite, and a strain-enhanced graphitization model is proposed. Moreover, the geographical distribution and the degree of graphitization are positively related to changes in the iron content of chlorite, suggesting a graphitization process promoted by mineral catalysis during metamorphism. A close spatial relationship exists between graphite mineral and chlorite occurrences when approaching the intrusive mass. The results of this research are important for understanding the role of tectonic stress and mineral catalysis on the genesis of coal-derived graphite.

High temperature surface graphitization of CVD diamond films and analysis of the kinetics mechanism

A plasma arc generator was used to heat treat the free-standing CVD diamond films at 1450–1900 °C. An Arrhenius curve was fit according to trends in the measured Raman peak intensity ratio of diamond to graphite as a function of heat treatment temperature, and the curve was extrapolated linearly. It was found that the extrapolation lines intersected at the Debye temperature, ΘD = 2021 K. By comparing the activation energies of diamond graphitization in literature and from different measurement modes in our study, it was found that the graphitization mechanisms were different on both sides of Debye temperature due to differences in the excited lattice vibration modes. When the heat treatment temperature was just below the Debye temperature, the graphitization process was promoted by generating vacancies or the breaking of single CC bonds, and the apparent activation energy was 366 ± 60 kJ·mol−1. When the heat treatment temperature was above the Debye temperature, the graphitization process was promoted by the simultaneous breaking of multiple CC bonds, and the apparent activation energy was 887 ± 141 kJ·mol−1. In combination with the morphology changes on the surface of the CVD diamond film after high temperature heat treatment, the mechanism of the micro-cyclic phase transition on the surface of the diamond film at temperatures lower than Debye temperature was summarized as follows. First, CC bonds on the diamond surface were activated and broken at high temperatures, and some diamond carbon atoms dissociated from solid phase sites to the gas phase by forming hydrocarbon free radicals. Then, the carbon atoms from these hydrocarbons entered the graphite lattice step by step to complete the spontaneous deposition of sp2 clusters.

Research on suppressing brittle fracture and implementing ductile mode cutting for improving surface quality at silicon wafers manufacturing

Single crystal silicon is an important basic material used to manufacture electronic and photovoltaic devices. Ductile mode of diamond wire sawing is a promising method for silicon wafering in order to produce wafers with minimal surface damage. To achieve ductile mode, the correct applying of cutting parameters and careful wire design is necessary. This study investigates the scratching of monocrystalline silicon by the abrasive particles of different geometry, which simulates the material removal process in diamond wire sawing. Diamonds, crushed and spherical tungsten carbide (WC) particles served as abrasives. Experiments show that spherical abrasives enhance ductile mode cutting significantly decreasing brittle damage when compared to irregular shape particles. Spherical WC particles permit to increase the critical load and critical cut depth of ductile-to-brittle transition from 5 to 10 times. The depth of the damaged subsurface layer decreased from 5 µm to 0.2 µm due to the absence of brittle cracks. A uniform regular distribution and appropriate suitable density of abrasive particles is obligatory for cracking reduction. For that, the method of diamond particles uniform deposition with the controlled density by a polymer binder combining high modulus and adhesive capacity with good flexibility was elaborated. The method includes preliminary diamond particles fixation on a thin resin layer providing high uniformity and subsequent strong fixation by a thicker resin layer. The research on ovalization of diamond particles was performed for smoothening cutting edges. The method is based on the activation of the graphitization process at sharp edges of particles under the action of metal salts at increased temperatures.

Self-standing graphitized hybrid Nanocarbon electrodes towards high-frequency supercapacitors

Carbon materials are considered as the ideal electrode materials for supercapacitors due to their diverse structure and nature. However, their poor frequency response is an obstacle to their application in high-frequency supercapacitors. Herein, an ultra-high temperature graphitization process at 2800 °C is proposed to fabricate carbon nanotubes/graphene hybrid films that are successfully employed as the electrode materials of high-frequency supercapacitors. By rational hybridization, the carbon nanotubes/graphene interlinked networks offer fast ion transport paths. Importantly, via a graphitization process at 2800 °C, the as-obtained hybrid films exhibit an ultrahigh in-plane conductivity of 491.81 S cm−1 and favorable out-plane conductivity of 27.98 mS cm−1. Such design brings the as-constructed high-frequency supercapacitors an unprecedented phase angle (up to −56.23°) and area capacitance (up to 230.56 μF cm−2) at 120 Hz, and their cut-off frequency can be nearly 30 times higher than that of films carbonization at 1600 °C. Such increases, further supported by density functional theory (DFT) calculations, are partly attributable to enhancements of ion response arising from the repair of edge defects of graphene. These findings will provide a new method in designing the structure of carbon electrodes for enhancing SCs frequency response performances.

Possibilities of Graphitization of Unburned Carbon from Coal Fly Ash

The paper presents the characteristics of products annealing at the temperatures of 2400 and 3000 °C of unburned carbon from coal fly ash in terms of its possible use as a starting material in the graphitization process. An amorphous substance (organic substance) with an admixture of some minerals has been found in samples subjected to graphitization. However, the graphite phase is dominant in products subjected to graphitization. Studies have also shown a diverse grain morphology in individual samples. The presence of plate-shaped and tube-shaped grains was found. As the graphitization temperature of the starting material increases (2400 and 3000 °C), the specific surface area in the graphitization products decreases. The total pore volume in the samples after the graphitization process was significantly lower than the pore volume of active carbons produced from other unburned carbon. Average pore diameter is similar to the pore diameter in active carbons. The reflectance value of the matrix for the sample graphitized at 3000 °C is characteristic for graphite. Unburned carbon from Polish fly ash can be used as the starting material for graphitization.

Study on Purification and Modification Processing Technology of Microcrystalline Graphite

With the continuous development of new energy and new material technology, social industries pay more and more attention to graphite resources, and the related new graphite materials and technologies emerge as the times require in scientific research and practical application. With the continuous development of high-tech graphite industry, the general high-carbon graphite products can not meet the requirements of all walks of life, so it is necessary to further improve the purity of graphite. Therefore, in the research and development process of new graphite materials and technologies, the first step is to realize the purification and processing of graphite raw materials, and then the functional modification processing of graphite can be completed, so that the new graphite materials can meet the application needs of various industries in the society in terms of particle size, morphology or performance. Based on this, the exploration of various purification methods of microcrystalline graphite and the processing technology of functional modification of graphite have practical and theoretical significance.

An investigation of accelerated graphitisation kinetics to improve the machinability of an experimental medium-carbon free-machining steel

Recent studies have shown that the graphitisation process in a medium‑carbon steel during high temperature annealing can be accelerated by alloying; the key alloying additions are Si and Al. In addition, the nucleation, morphology and dispersion of graphite particles or nodules are observed to be affected by the pre-anneal microstructure, for example, either ferrite-pearlite, bainite or martensite, as well as the annealing time. The accelerated graphitisation kinetics and microstructural effects are revealed by light optical and electron microscopy, and in parallel with this, are also reflected by the hardness values as dictated by the normal tempering reactions and balance between the graphite and remaining carbides. Thus the extent of graphitisation is shown to influence the machinability of the experimental carbon steel. Indicative machinability was measured by tool wear during drill testing. The drill tests also indicated that optimisation of steel composition and heat treatment could potentially develop promising machinability comparable to existing commercial free-machining steel SAE 1117. Under the conditions of the drill tests conducted, graphitising from the starting bainitic microstructure also resulted in measured tool wear not too dissimilar to that of leaded free-machining steel SAE 12L14.

Enhancement of Bromine Kinetics Using Pt@Graphite Felt and Its Applications in Zn-Br2 Redox Flow Battery

The high surface area electro-catalysts facilitate the enhanced electrochemical reactions by providing more active sites. Here, introducing noble Pt particles on the active electrode (graphite felt) highly improved the reaction kinetics of positive redox couple (Br2/Br−) in a zinc bromine flow battery. The noble Pt metal significantly improvises the electron transfer reaction between bromine and Pt loaded GF. The graphite felt modification process was carried out by simple synthesis process. The Pt content was optimized based on the enhancement of the reaction kinetics of Br2/Br−. The electrode with ∼1% Pt at the electrode showed a maximum specific power density of 1640 mW cm−2. The flow cell at low loading of Pt also delivered an excellent cycling performance over 300 cycles. The flow cell delivered maximum Coulombic and Energy efficiency of ∼96, ∼83%, respectively even at 300th cycle. It is clearly seen that the cell having optimum content of Pt on the electrode surface is proved as suitable positive electrode for obtaining good performance of Zn-Br2 flow cell.

Laser ablation of graphite with near infrared microsecond pulses

Laser processing of polycrystalline porous graphite through micro- to millisecond pulses with 1 µm wavelength is investigated. The study aims at finding the best compromise between the efficiency of the process (ablation rate) and the quality (reduced heat-affected zone) for drilling and cutting applications. Our experimental approach is based on experiments involving a monomode kW ytterbium fibre laser (1080 nm) coupled with a laser scanning system. This system is used for parametric studies on pulse duration, power, repetition rate and scanning speed on samples that are analysed with scanning electron microscopy. To improve the understanding of the underlying physical phenomena and processes involved, a finite element numerical model is developed, taking into account energy deposition through optical ray tracing, heat transfer, sublimation of the material and crater formation. Based on these experimental and numerical tools, we identify some optimum parameters to fabricate high aspect ratio shapes in graphite samples of 1.5 mm thickness with excellent edge quality and minimal heat-affected zone. Laser processing under vacuum atmosphere is also studied and exhibit no difference in behaviour compared to ambient atmosphere.

Development of rGO/Fe3O4 Composites as Glucose Biosensors

The rGO/Fe3O4 composite is one type of composites that can be used as a biosensor material, especially glucose sensors. The main ingredients of the composite synthesis are graphite and iron sand. The synthesis process of Fe3O4 was done using the coprecipitation method, while the graphite oxidation process was accomplished using the modified Hummer's method. The composites were formed using the ex-situ wet mixing method. The formed iron sand and graphite were characterized using FTIR and XRD, and it was found that Fe3O4 was formed from the appearance of the Fe-O bond, the oxidation process of graphite was seen from the appearance of the C=O bond, and the detection of Fe peaks corresponded to the cubic crystal plane. Likewise, the composites formed were also characterized using FTIR and XRD for identification of the rGO/Fe3O4 composite formation. It was proven from the presence of Fe-O and C-O bonds and the appearance of an amorphous peak of rGO in the XRD results. The performance of the rGO/Fe3O4 composites as the glucose biosensor was examined by varying the mass of Fe3O4 on the composite, using UV-Vis spectroscopy. The performance of the rGO/Fe3O4 composite biosensor in absorbing glucose reached optimum at a mass variation of 0.3 grams of Fe3O4, as demonstrated by by the lowest absorbance peak with an intensity of 0.0048 at a wavelength of 440 nm, corresponding to glucose entrappment of 7.1 mg/gram.

Graphene oxide/Au nanoparticles: Synthesis, properties, and application: A mini‐review

There has been rapid growth in research activities on the potential of graphene oxide/Au (GO:Au) composite for different applications. The GO:Au composite has been widely explored in applications such as biomedicine, electrochemical biosensors, optical limiters, and organic dye degradation. The increased interest in GO:Au for these applications is the consequence of harvesting the electronic bonding structure that is due to the formation of sp3 CC clusters from defected sp2 C═C and attachment of Au atoms onto the C═C carbon matrix. The defection of the sp2 cluster of GO can be achieved by the method of improved synthesis and functionalization with Au surfactants. The current review explores an overview of the different synthesis techniques for producing GO:Au composites, which is an important factor in controlling the particle and size distribution of the composites. The electronic, electrical, and magnetic properties of GO:Au composites are covered as it relates to photochemical, memristive, and biomedical imaging applications. The low coercivity and remanence are consistent with superparamagnetic behavior. Although, GO:Au-nanocomposite (NC) are widely explored for biomedicine and drug delivery applications, future applications of the composite can be useful for magnetic resonance imaging owing to the superparamagnetic behavior. The future possibilities of GO:Au-NP are promising in the field of bioimaging and electronic devices. The electrical property of GO:Au-NC can be fused with its electrochemical property for supercapacitor applications. In some cases, GO:Au-NC is used as an anchor material with conducting polymers to enhance the supercapacitor properties. Furthermore, the synthesis of mono-disperse few-layer graphene is still challenging owing to economic cost and the graphite exfoliation process. The review of GO:Au composite from a material physics perspective aims to elucidate the current trends as well the future possibilities offered by the composite for various promising applications. Novelty Statement This review focused on the graphene oxide-gold nanocomposite which is an outstanding composite material for different applications. The overview of graphene oxide/Au nanoparticles was first presented in this work. The synthesis, properties, and applications of graphene oxide/gold nanocomposites were emphasized. The disadvantages and promising prospect of GO:Au nanocomposites for the ferroelectric and magnetic resonance imaging applications were highlighted.

An innovative flake graphite upgrading process based on HPGR, stirred grinding mill, and nanobubble column flotation

Physical upgrading of graphite is typically achieved with many stages of grinding and flotation to produce a concentrate with approximately 95% carbon grade. An innovative grinding and column flotation process has been developed for efficient graphite upgrading to substantially simplify the process flowsheet and reduce operating costs. In this process, a high-pressure grinding roller (HPGR) and a stirred mill were employed as primary comminution techniques and a nanobubble flotation column as a key separation process. The results obtained with a crystalline flake graphite sample with a carbon grade of 11.15% show that the novel process can produce a concentrate with 94.82% carbon grade and 97.89% recovery from an open circuit of one rougher and two cleaner flotation stages. Scanning electron microscope (SEM) microphotographs indicate that HPGR offers the advantage of more effective protection of graphite flakes during crushing. Grinding test results show that stirred mill could not only protect graphite flakes but also promote the efficient liberation of graphite. Compared with the traditional flotation process, nanobubble flotation can effectively recover ultrafine graphite. The new process possesses a number of important advantages over the traditional method, including substantially higher graphite recovery, greatly simplified process flowsheet, better protection of flake size, reduced reagent consumption and process costs, etc.

Structure of Coal-Derived Metal-Supported Few-Layer Graphene Composite Materials Synthesized Using a Microwave-Assisted Catalytic Graphitization Process.

Metal-supported few-layer graphene (FLG) was synthesized via microwave-assisted catalytic graphitization owing to the increasing demand for it and its wide applications. In this study, we quickly converted earth-abundant and low-cost bituminous coal to FLG over Fe catalysts at a temperature of 1300 °C. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and N2 adsorption–desorption experiments were performed to analyze the fabricated metal-supported FLG. The results indicated that the microwave-irradiation temperature at a set holding-time played a critical role in the synthesis of metal-supported FLG. The highest degree of graphitization and a well-developed pore structure were fabricated at 1300 °C using a S10% Fe catalyst for 20 min. High-resolution transmission electron microscopy analysis confirmed that the metal-supported FLG fabricated via microwave-assisted catalytic graphitization consisted of 3–6 layers of graphene nanosheets. In addition, the 2D band at 2700 cm−1 in the Raman spectrum of the fabricated metal-supported FLG samples were observed, which indicated the presence of few-layer graphene structure. Furthermore, a mechanism was proposed for the microwave-assisted catalytic graphitization of bituminous coal. Here, we developed a cost-effective and environmental friendly metal-supported FLG method using a coal-based carbonaceous material.

Design of Experiments and Optimization of Laser-Induced Graphene.

Realization of graphene-based sensors and electronic devices remains challenging, in part due to integration challenges with current fabrication and manufacturing processes. Thus, scalable methods for in situ fabrication of high-quality graphene-like materials are essential. Low-cost CO2 laser engravers can be used for site-selective conversion of polyimide under ambient conditions to create 3-D, rotationally disordered, few-layer, porous, graphene-like electrodes. However, the influences of non-linear parameter terms and interactions between key parameters on the graphitization process present challenges for rapid, resource-efficient optimization. An iterative optimization strategy was developed to identify promising regions in parameter space for two key parameters, laser power and scan speed, with the goal of optimizing electrode performance while maximizing scan speed and hence fabrication throughput. The strategy employed iterations of Design of Experiments Response Surface (DoE-RS) methods combined with choices of readily measurable parameters to minimize measurement resources and time. The initial DoE-RS experiment set employed visual response parameters, while subsequent iterations used sheet resistance as the optimization parameter. The final model clearly demonstrates that laser graphitization through raster scanning is a highly non-linear process requiring polynomial terms in scan speed and laser power up to fifth order. Two regions of interest in parameter space were identified using this strategy: Region 1 represents the global minimum for sheet resistance for this laser (∼16 Ω/sq), found at a low scan speed (70 mm/s) and a low average power (2.1 W) . Region 2 is a local minimum for sheet resistance (36 Ω/sq), found at higher values for scan speed (340 mm/s) and average power (3.4 W), allowing ∼5-fold reduction in write time. Importantly, these minima do not correspond to constant ratios of average laser power to scan speed. This highlights the benefits of DoE-RS methods in rapid identification of optimum parameter combinations that would be difficult to discover using traditional one-factor-at-a-time optimization. Verification data from Raman spectroscopy showed sharp 2D peaks with mean full-width-at-half-maximum intensity values <80 cm–1 for both regions, consistent with high-quality 3D graphene-like carbon. Graphene-based electrodes fabricated using the parameters from the respective regions yielded similar performance when employed as capacitive humidity sensors with hygroscopic dielectric layers. Devices fabricated using Region 1 parameters (16 Ω/sq) yielded capacitance responses of 0.78 ± 0.04 pF at 0% relative humidity (RH), increasing to 31 ± 7 pF at 85.1% RH. Region 2 devices (36 Ω/sq) showed comparable responses (0.88 ± 0.04 pF at 0% RH, 28 ± 5 pF at 85.1% RH).

The pseudo-capacitance of graphitic nanoribbons aerogel with encapsulated Fe nanoparticles

A graphitic nanoribbons (GNRs) encapsulated with Fe nanoparticles (NPs) hybrids derived from pyrrole and FeCl3 through polymerization, freeze drying and catalytic graphitization process showed excellent capacitive and cycle performance using as pseudo-capacitive material for supercapacitors (SC). The precursor of FeCl3 ingeniously served as oxidant for polymerization of pyrrole, catalyst for graphitization of polypyrrole and pseudo-capacitive material for SC successively. The obtained Fe@GNRs electrode exhibited a remarkable pseudocapacitance performance with a high specific capacitance of 526.7 F g−1 at a discharge current density of 1 A g−1. GNRs obtained by catalytic graphitization of polypyrrole under metallic Fe could effectively protect and stabilize the encapsulated Fe NPs showing ~100% capacitance retention rate after 10,000 cycles under 10 A g−1.