Disordered Carbon Material Research Articles

A Facile Method to Transform Pickled Olive Wastes Into Sulfur-Doped Carbon for Sodium-Ion Battery Electrode.

This work provides a novel, low-cost, and effective method to prepare disordered carbon materials for advanced sodium-ion batteries using biomass. A large amount of olive stone waste is yearly produced in the world, and it could be re-used for fine applications other than fuel for heat production. After treatment with sulfuric acid solution and carbonization process, wastes of olive stone are efficiently transformed into optimized carbon electrode material. XRD, XRF and XPS, electron microscopy, and physical gas adsorption are used for the compositional, microstructural, and textural characterization of the carbons. During the synthesis, impurities are removed, C-S links are formed and micropores pores are created. Sulfuric acid acts like S-dopant. The latent pores, or pores closed to nitrogen, can be found using CO2 adsorption, and are very suitable for accommodation for sodium. The results reveal that the reversible capacity is raised from ca. 200 mAh g-1 to ca. 250 mAh g-1 for the carbon obtained through treatment with sulfuric acid. The improved electrochemistry is the result of the s-doping and the porosity.

Hollow carbon nanospheres with optimized nitrogen configuration controlled by heteroatom doping for high-performance potassium-ion storage

As is known, the electrochemical energy storage capability of carbon-based material significantly depends on its intrinsic nitrogen configuration. In this work, the nitrogen configuration in hollow carbon skeleton was controlled by heteroatom phosphorus doping, realized in successfully synthesized N–P co-doping hollow carbon nanospheres (HCNS-NP) samples. When used in K-ion battery, the prepared HCNS-NP electrode retains a discharge capacity of ∼338.8 mA h g−1 at a current density of 100 mA g−1. Furthermore, it achieves a reversible capacity of 180.6 mA h g−1 at a high current density of 1000 mA g−1, even after 1000 cycles. Both experimental and DFT results support that phosphorus doping promote the formation of pyrrole-N within the samples, instead of pyridine-N or graphite-N, which accounts for the enhancement in K-ion conductance and eventually K-ion storage performance. The research opens up a new platform in modifying nitrogen configurations in disordered carbon materials, which should be attractive to the electrochemical, catalysis and material communities.

Identification and classification of disordered carbon materials in a composite matrix through machine learning approach integrated with Raman mapping

Identification and classification of different types of highly disordered carbon materials present in a polymer matrix with similar Raman spectra have been carried out using a machine learning approach. Convolutional neural network (CNN) has been used for the classification of disordered carbon materials such as graphene oxide (GO), functionalized carbon nanotube (f-CNT), carbon fiber (Cf), carbon black (CB), pyrolytic carbon (PyC), coke, and mesocarbon microbeads (MCMB). The hyperparameters of the machine learning model have been optimized by the Bayesian optimization algorithm. CNN gave an accuracy of 91.9 %, F1 score of 92 %, precision of 92.1 %, recall of 92 % and area-under-curve (AUC) of 0.99. Gradient-weighted Class Activation Mapping (Grad-CAM) has been utilized for getting the explainability in the classification process of the CNN model. The CNN along with Raman area scanning could successfully map different disordered carbon materials in the polymer matrix composite.

CO2 adsorption studies on spherical carbon derived from resorcinol-formaldehyde resin and sugars

A highly porous spherical carbon material produced from resorcinol-formaldehyde resin and sugars was applied as an efficient CO2 sorbent. The effect of the modification with different sugars on the physicochemical properties of the obtained materials was investigated. As a result, very efficient CO2 adsorbents have been obtained. Produced materials expressed high CO2 uptake values, reaching 6.79 mmol/g at 0 oC and 1 atm for the sample modified with xylitol. In addition, the selectivity of the sugar modified samples towards CO2 has been significantly improved in comparison to the reference resorcinol-formaldehyde resin derived sample. The incorporation of sugars resulted in changes in the crystallographic structure of the samples leading to obtaining more disordered carbon materials.

Pre-Oxidation Strategy Transforming Waste Foam to Hard Carbon Anodes for Boosting Sodium Storage Performance.

Large reserves, high capacity, and low cost are the core competitiveness of disordered carbon materials as excellent anode materials for sodium-ion batteries (SIBs). And the existence and improper treatment of a large number of organic solid wastes will aggravate the burden on the environment, therefore, it is significant to transform wastes into carbon-based materials for sustainable energy utilization. Herein, a kind of hard carbon materials are reported with waste biomass-foam as the precursor, which can improve the sodium storage performance through pre-oxidation strategy. The introduction of oxygen-containing groups can promote structural cross-linking, and inhibit the melting and rearrangement of carbon structure during high-temperature carbonization that produces a disordered structure with a suitable degree of graphitization. Moreover, the micropore structure are also regulated during the high-temperature carbonization process, which is conducive to the storage of sodium ions in the low-voltage plateau region. The optimized sample as an electrode material exhibits excellent reversible specific capacity (308.0mAhg-1) and initial Coulombic efficiency (ICE, 90.1%). In addition, a full cell with the waste foam-derived hard carbon anode and a Na3V2(PO4)3 cathode is constructed with high ICE and energy density. This work provides an effective strategy to conversion the waste to high-value hard carbon anode for sodium-ion batteries.

Application of the trinary discretization method for the structural analysis of natural disordered sp2 carbon

High-resolution transmission electron microscopy (HRTEM) is one of the most effective methods for analyzing the nanoscale structure of disordered carbon. Mathematical processing of HRTEM images made the quantification and description of the complex structure of disordered carbon more reliable. This work demonstrates the HRTEM image processing algorithm applied to four naturally occurring substances with a disordered carbon structure and different electrically conductive properties. The result of the algorithm is a quantitative estimation of the structural characteristics of disordered carbon by the method of structural discretization over three degrees of ordering. The algorithm consists of two main parts: (a) HRTEM image processing, which generates a trinary image, and (b) quantification, which generates nanoscale structure statistics. The reliability (reproducibility) of the results is about 66% and does not depend on the difference in the physical properties of the samples. The proposed image analysis algorithm can be applied to any similar disordered materials to characterize the structure at the nanometer scale, used to build models of disordered carbon materials and describe some of the physicochemical properties.

Insights into the carbonization mechanism of bituminous coal-derived carbon materials for lithium-ion and sodium-ion batteries

Despite recent interest in the low-temperature carbonization of coal to prepare disordered carbon materials for the anodes of lithium-ion (LIBs) and sodium-ion batteries (SIBs), the carbonization mechanism is still poorly understood. We selected bituminous coal as the raw material and investigated the chemical, microcrystal, and pore structure changes during the carbonization process from coal to the resulting disordered carbon. These structural changes with temperature below 1 000 °C show an increase in both interlayer spacing (3.69–3.82 Å) and defect concentration (1.26–1.90), accompanied by the generation of a large amount of nano-microporous materials. These changes are attributed to the migration of the local carbon layer and the release of small molecules. Furthermore, a decrease in interlayer spacing and defect concentration occurs between1 000 °C and 1 600 °C. In LIBs, samples carbonized at 1 000 °C showed the best electrochemical performance, with a reversible capacity of 384 mAh g−1 at 0.1 C and excellent rate performance, maintaining 170 mAh g−1 at 5 C. In SIBs, samples carbonized at 1 200 °C had a reversible capacity of 270.1 mAh g−1 at 0.1 C and a high initial Coulombic efficiency of 86.8%. This study offers theoretical support for refining the preparation of carbon materials derived from coal.

Characterization of Fine Structure and Mechanical Properties of the Disordered Carbon Materials Synthesized from C60 Fullerite under High Pressure

Characterization of Fine Structure and Mechanical Properties of the Disordered Carbon Materials Synthesized from C60 Fullerite under High Pressure

The effect of structure on the conductivity of disordered carbon (the case of graphene-containing shungite)

Understanding the mechanisms of conductivity in disordered carbon materials is one key to creating applied materials based on them. We present a new promising approach to quantitatively assessing the effect of structural parameters on the conductivity of disordered sp2 carbon materials within the framework of a simplified current tube model. Stacks of graphene layers of complex shape and chaotic in contacts as an aggregate of sequentially located and parallel tubes were presented. This approximation made it possible to obtain a reliable quantitative estimate of the influence of the stacks size of graphene layers and their size distribution, as well as the size of the gaps between the stacks on the conductivity. The theoretical positions of the model were tested using the experimentally obtained parameters of the structure of two typical natural disordered carbon materials (shungites).

Continuous-wave and pulsed EPR studies of glass-like carbon with high spin concentration: Evidence for triplet states

Glass-like carbons (GLCs) are a large group of disordered carbon materials which have applications in various fields, but not all their properties are well characterized. In particular, they have high concentration of paramagnetic centers (PCs) which are easily observed by electron paramagnetic resonance (EPR). However, an apparently simple EPR spectrum, together with its peculiarities caused by high electrical conductivity, make it difficult to identify the PCs and their origin remains unknown. To resolve these unsettled questions, in this work we use the vacuum Rabi splitting and Rabi oscillations which so far have not been applied to study these materials by the continuous wave (CW) and pulsed EPR. GLC produced by pyrolysis of phenol-formaldehyde resin at 1120 K was studied in the temperature range of 4.3–300 K. Using the Rabi splitting we found conditions for undistorted registration of CW EPR spectra and determined spin concentration (1×1020 spin/g). The temperature dependence of the EPR susceptibility shows the coexistence of Pauli paramagnetism due to conduction electrons and the Curie-type paramagnetism of thermally activated PCs with the activation energy of 5.7 cm-1. These PCs may be excited triplet states, the presence of which is revealed by Rabi oscillations in the pulsed EPR.

Structural transformation of porous and disordered carbon during ball-milling

Mechanical ball-milling is a commonly used method to shattering crystals or introducing defects in carbon materials. But herein, we observe that the highly porous and disordered carbon lattice of activated carbon is converted to graphitic structure during ball-milling, along with the introduction of oxygen in the bulk phase. The well-developed pores are gradually eliminated, leading to obviously decreased surface area from 1364 to 156 m2 g-1 and improved compaction density from 0.573 to 1.423 g cm-3. Due to the continuous particle cleavage, re-assembly, and cold-welding, the as-formed carbon blocks show 2 times larger in size and 4 times higher bulk oxygen content. This simultaneous crystallinity enhancement and oxygen functionalization is barely observed in other methods. The mechanism is that highly reactive carbon radicals generated by mechanical cleavage of carbon skeleton enable atom rearrangement to form large graphitic domains or being terminated by oxygenated groups. Interestingly, the capacitive energy storage performance of the ball-milled activated carbon is changed from electric-double-layer to pseudo-capacitance in aqueous electrolyte, showing significantly improved volumetric capacitances and high-rate performance. Our work provides a theoretical guidance for mechanochemistry of porous and disordered carbon materials.

Hard Carbons as Anodes in Sodium-Ion Batteries: Sodium Storage Mechanism and Optimization Strategies.

Sodium-ion batteries (SIBs) are regarded as promising alternatives to lithium-ion batteries (LIBs) in the field of energy, especially in large-scale energy storage systems. Tremendous effort has been put into the electrode research of SIBs, and hard carbon (HC) stands out among the anode materials due to its advantages in cost, resource, industrial processes, and safety. However, different from the application of graphite in LIBs, HC, as a disordered carbon material, leaves more to be completely comprehended about its sodium storage mechanism, and there is still plenty of room for improvement in its capacity, rate performance and cycling performance. This paper reviews the research reports on HC materials in recent years, especially the research process of the sodium storage mechanism and the modification and optimization of HC materials. Finally, the review summarizes the sterling achievements and the challenges on the basis of recent progress, as well as the prospects on the development of HC anode materials in SIBs.

Effects of olefinic compounds on the thermal transformation for FCC slurry oil: Evolution pattern and mechanism

FCC decant oil was always used as the raw material for the preparation of high-value-added carbonaceous materials. There is little disagreement that the free radical mechanism induces thermal polymerization reactions between reactant molecules and intermediate species, which leads to the formation of carbonaceous mesophase in the early stage of carbonization. Olefinic hydrocarbons were recently found to be widely distributed in FCC decant oil in our previous research, and these chemically active compounds usually possess weak π-bonds in molecules and thus potentially form free radicals easily, which may impact the carbonization performance dramatically. This research investigated the effects of olefinic compounds on the preparation of needle coke from FCC decant oil, as well as the corresponding mechanism in depth combined with the evolution pattern of the intermediate species during liquid carbonization. ESR analyses were adopted to evaluate the variation of the concentration of stable free radicals. Stable free radical concentration varied greatly in diverse polymerizing systems along with the carbonization process. Olefin showed a significant effect on the stable free radical concentration during carbonization. The stable free radical concentration of the polymerizing system derived from FCC decant oil was 3.32 × 1020 spins/g when the reaction time was 4 h. But with 3 wt% addition of 2-vinylnaphthalene and squalene in FCC decant oil, the stable free radical concentration increased to 2.14 × 1021 spins/g and 1.33 × 1021 spins/g, respectively, with the same reaction time. Meanwhile, the olefins conjugated with aromatic rings shown more obvious effect on the generation of free radicals. Olefinic compounds can lead to a high generation rate of free radicals and significantly high stable free radical concentration in the polymerizing system which then promote the formation of disordered carbon materials. Besides, plenty of fine particles appeared between mesophase spheres with the addition of olefinic hydrocarbons, and then impeded the coalescence between mesophase spheres. Effect mechanism for olefin on the development of carbonaceous mesophase was proposed accordingly. In sum, the content of olefinic compounds in raw materials should be limited for reaching the requirements of the synthesis of carbon materials with superior structures, in which the content of olefinic compounds should be less than 1 wt% at least based on the research in this paper.

Eco-Friendly Synthesis of 3D Disordered Carbon Materials for High-Performance Dual Carbon Na-Ion Capacitors.

An eco-friendly and sustainable salt-templating approach was proposed for the production of anode materials with a 3D sponge-like structure for sodium-ion capacitors using gluconic acid as carbon precursor and sodium carbonate as water-removable template. The optimized carbon material combined porous thin walls that provided short diffusional paths, a highly disordered microstructure with dilated interlayer spacing, and a large oxygen content, all of which facilitated Na ion transport and provided plenty of active sites for Na adsorption. This material provided a capacity of 314 mAh g-1 at 0.1 A g-1 and 130 mAh g-1 at 10 A g-1 . When combined with a 3D highly porous carbon cathode (SBET ≈2300 m2 g-1 ) synthesized from the same precursor, the Na-ion capacitor showed high specific energy/power, that is 110 Wh kg-1 at low power and still 71 Wh kg-1 at approximately 26 kW kg-1 , and a good capacity retention of 70 % over 10000 cycles.

Temperature driven structural transition in the nickel-based catalytic graphitization of coconut coir

Biomass waste is considered as a renewable, low-cost, and environmental friendly carbon source. However, converting a largely disordered carbon materials from biomass wastes into a highly crystalline graphitic carbon nanostructure with low-energy consumption process remains a challenge. Here, we report a simple and low energy process to transform the amorphous carbon structure of coconut coir from Indonesian biomass waste into graphitic nanostructure. A high crystalline graphitic nanostructure has been successfully obtained through two-step process consisting of (1) carbonization process at 500 °C to produce amorphous charcoal, followed by (2) nickel-based catalytic graphitization process at various temperature of 1000 °C to 1300 °C. It is important to note that the temperature process is a main factor in the structural transformation from amorphous to graphitic nanostructures. The structural transformation during catalytic graphitization process was investigated as a function of heat treatment temperature using X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that the carbon structure of coconut coir start to transform from amorphous to ordered graphitic nanostructure at 1200 °C, a temperature lower than that of conventional graphite production, with the highest degree of graphitization (82.16%) and IG/ID ratio of 1.16. Observation using high resolution transmission electron microscopy (HRTEM) reveal the well-defined lattice fringes of graphitic nanostructures with an interplanar distance of 0.3369 nm corresponding to the (0 0 2) crystal plane of pure graphite (0.3354 nm) and less than the disorder carbon (0.3440 nm). In conclusion, this simple process and low energy successfully convert the coconut coir waste into a higher value-added product of graphitic materials as well as reduce the environmental impact of coconut waste.

Insights into Electrocatalytic Oxygen Reduction Via a Dominant Two-Electron-Transfer Process on Sulfur-Doped Disordered Carbon

We propose a simple sulfur-doped disordered carbon material which catalyzes the oxygen reduction reaction (ORR) predominantly via a two-electron-transfer process. All the prepared catalysts exhibit...

Direct evidence for eoarchean iron metabolism?

Metasedimentary rocks from Isua, West Greenland (> 3,700 million years old) contain carbonaceous compounds, compatible with a biogenic origin (Hassenkam, Andersson, Dalby, Mackenzie, & Rosing, 2017; Ohtomo, Kakegawa, Ishida, Nagase, & Rosing, 2014; Rosing, 1999). The metamorphic mineral assemblage with garnet and quartz intergrowths contains layers of carbonaceous inclusions contiguous with carbon-rich sedimentary beds in the host rock. Previous studies (Hassenkam et al., 2017; Ohtomo et al., 2014; Rosing, 1999) on Isua rocks focused on testing the biogenic origin of the carbonaceous material, but here we searched for evidence which could provide new insights into the nature of the life that generated this carbonaceous material. We studied material trapped in inclusions armoured within quartz grains inside garnet porphyroblasts by non-destructive ptychographic X-ray nanotomography (PXCT). The 3D electron density maps generated by PXCT were correlated with maps from X-ray fluorescence tomography and micro-Raman spectroscopy. We found that the material trapped inside inclusions in the quartz grains consist of disordered carbon material encasing domains of iron-rich carbonaceous material. These results corroborate earlier claims (Hassenkam et al., 2017; Ohtomo et al., 2014; Rosing, 1999) for biogenic origins and are compatible with relics of metamorphosed biological material originally containing high iron/carbon ratios, comparable to ratios found in most extant organisms. These iron-rich domains represent the oldest evidence for organic iron complexes in the geologic record and are consistent with Fe-isotopic evidence for metabolic iron fractionation in>3,700Ma Isua banded iron formation (Czaja et al., 2013; Whitehouse & Fedo, 2007).

Heat-treated glassy carbon under pressure exhibiting superior hardness, strength and elasticity

Glassy carbon (GC) is a type of non-graphitizing disordered carbon material at ambient pressure and high temperatures, which has been widely used due to its excellent mechanical properties. Here we report the changes in the microstructure and mechanical properties of GC treated at high pressures (up to 5 GPa) and high temperatures. The formation of intermediate sp2–sp3 phases is identified at moderate treatment temperatures before the complete graphitization of GC, by analyzing synchrotron X-ray diffraction, Raman spectra, and transmission electron microscopy images. The intermediate metastable carbon materials exhibit superior mechanical properties with hardness reaching up to 10 GPa and compressive strength reaching as high as 2.5 GPa, nearly doubling those of raw GC, and improving elasticity and thermal stability. The synthesis pressure used in this study can be achieved in the industry on a commercial scale, enabling the scalable synthesis of this type of strong, hard, and elastic carbon materials.

Morphological Specific Features of (100)-Textured Polycrystalline Diamond Films

The morphological specific features of (100)-textured polycrystalline diamond films, grown by chemical vapor deposition (CVD) and consisting of micrometer-sized crystallites and disordered carbon material, have been investigated. The grown films were heated in air to a temperature providing selective removal of low-ordered carbon material. The structural and morphological specific features of the samples were analyzed by electron microscopy. A model of the film-growth process is developed based on the experimental data obtained. The correspondence of the computer simulation based on this model with the experimental data confirms validity of this model.

Microstructure engineering towards porous carbon materials derived from one biowaste precursor for multiple energy storage applications

Microstructure regulation is of great significance to carbon based materials for desired applications in the fields of energy storage and conversion. Herein, we report the microstructure engineering towards porous carbon materials from the same precursor enabling multiple energy storage applications. Highly disordered carbon materials (HDCMs) and graphene-like carbon materials (GLCMs) can be obtained from one biomass waste of peanut dregs. Thanks to the ultrahigh surface area, relative narrow pore size, and disordered structure, the as-resulted HDCMs display high hydrogen uptake of 3.03%, and high specific capacitance of 449 F g−1 at a current density of 0.5 A g−1, outstanding rate capability as well as remarkable cycling performance. As anode materials for LIBs, the resultant GLCMs exhibit reversible capacity of 731 mAh g−1 at a current density of 100 mA g−1 and excellent cycling stability, owing to the high graphitization, lamellar structure, and dominant mesoporosity. These results demonstrate that this microstructural engineering approach is promising and efficient to design and controllable preparation of porous carbon materials for multiple desirable energy storage applications.