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Carbon black (CB) has wide range of industrial applications, including in the manufacturing of automobile tires, rubber products, inks, and plastics. To improve the properties of the target products and establish recycling systems, it must be fully characterized. However, characterization of CB is challenging owing to its structural complexity and the limitation of conventionally used experimental techniques, especially for surface structures at the nanoscale. In this study, we characterized the surface structures of two commercial CB via atomic force and scanning tunneling microscopy. Analysis of well-dispersed aggregates on atomically flat solid surfaces revealed primary particles of diverse sizes. The particle surfaces lacked edges, grooves, and steps that should be observed between stacked graphene sheets, which contradicts the widely accepted crystallite model. Observed images suggest that the graphene sheets exhibit a size distribution, inferring that multiple non-uniformly sized small graphene sheets are stacked turbostratically, with each sheet displaying a localized curvature rather than the ideal planar form. Varying size of sheets and curvature indicate the presence of a decent number of edges terminated with hydrogen and oxygen-containing functional groups. This interpretation was corroborated by conventional spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and infrared absorption spectroscopy.

Lithium–oxygen (Li–O2) batteries with ultra-high theoretical specific energy (3500 Wh kg−1) have attracted significant attention, but the sluggish electrochemical processes of discharge product Li2O2 lead to poor cycling stability. Redox mediators (RMs) as soluble catalysts are widely used to assist with the electrochemical formation/decomposition of Li2O2. However, the shuttle effect of RMs causes severe deterioration of both RMs and Li metal anodes. Herein, for the first time we synthesize a lithiated zeolite-based protective layer on Li anodes to mitigate the shuttle effect of 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) in Li–O2 batteries. The protective layer successfully blocks the migration of TEMPO toward the Li anode owing to the angstrom-level aperture size of lithiated zeolite. Due to the excellent redox-mediator-sieving capability of the protective layer, the cycle life of the Li−O2 batteries is significantly prolonged more than ten times at a current density of 250 mA g−1 and a limited capacity of 500 mA h g−1. This work demonstrates that the lithiated zeolite-based protective layer capable of molecular sieving is a facile and scalable way to mitigate the shuttle effect of RMs in Li–O2 batteries.

To further improve the energy density and reliability of carbon based electrochemical capacitors, such as electric double-layer capacitors and lithium ion capacitors, it is necessary to increase both the electric double layer capacitance and stability of the porous carbon electrodes used in the capacitors. Not only the specific surface area and pore size, but also the pore shape and pore size distribution, and the analytical methods to properly evaluate the pore structure should be considered when improving the capacitance. In the case of the high stability to high voltage charging, it is important to design and control the three-dimensional structure of the electrode as well as the crystal structure and crystallinity of the carbon. In this review, some advanced examples of the recent research on these topics will be discussed.

This mini-review provides an in-depth analysis of the formation and post-processing of nanoporous graphene materials via methane chemical vapor deposition (CH4-CVD) using nanostructured metal oxide templates, including Al2O3, MgO, and SiO2. Initially, the formation of graphene sheets is discussed in terms of the role of CH4-CVD, the influence of templates, and the underlying mechanism for tailoring the structures of the graphene-based materials. Following this, the discussion extends to the post-graphene formation process. We focus on key steps, including template removal and graphene repair via zipping reactions at high temperatures. Additionally, we evaluate the conditions to prevent undesired structural transformations. The correlation between the structural features and transformations occurring during post-processing is also examined. The materials fabricated through these methods exhibit impressive properties of high porosity, minimal edge sites, superior oxidation resistance, and elasticity, positioning them as promising materials in various applications.

Abstract The electrochemical properties of metal oxides are very attractive and fascinating in general, making them a potential candidate for supercapacitor application. Vanadium oxide is of particular interest because it possesses a variety of valence states and is also cost effective with low toxicity and a wide voltage window. In the present study, vanadium oxide nanorods were synthesized using a modified sol–gel technique at low temperature. Surface morphology and crystallinity studies were carried out by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy analysis. To the best of our knowledge, the as-prepared nanorods were tested with magnesium ion based polymer gel electrolyte for the first time. The prepared supercapacitor cell exhibits high capacitance values of the order of ~ 141.8 F g−1 with power density of ~ 2.3 kW kg−1 and energy density of ~ 19.1 Wh kg−1. The cells show excellent rate capability and good cycling stability.

Abstract The rational design of a stable and catalytic carbon cathode is crucial for the development of rechargeable lithium‐oxygen (LiO2) batteries. An edge‐site‐free and topological‐defect‐rich graphene‐based material is proposed as a pure carbon cathode that drastically improves LiO2 battery performance, even in the absence of extra catalysts and mediators. The proposed graphene‐based material is synthesized using the advanced template technique coupled with high‐temperature annealing at 1800 °C. The material possesses an edge‐site‐free framework and mesoporosity, which is crucial to achieve excellent electrochemical stability and an ultra‐large capacity (>6700 mAh g−1). Moreover, both experimental and theoretical structural characterization demonstrates the presence of a significant number of topological defects, which are non‐hexagonal carbon rings in the graphene framework. In situ isotopic electrochemical mass spectrometry and theoretical calculations reveal the unique catalysis of topological defects in the formation of amorphous Li2O2, which may be decomposed at low potential (∼ 3.6 V versus Li/Li+) and leads to improved cycle performance. Furthermore, a flexible electrode sheet that excludes organic binders exhibits an extremely long lifetime of up to 307 cycles (>1535 h), in the absence of solid or soluble catalysts. These findings may be used to design robust carbon cathodes for LiO2 batteries.

Porous carbon materials are used widely in catalysis, electrochemistry, or as sorbents, but pore size control continues to be a challenge in their syntheses. Here the authors show that the 3D molecular structure of the carbon sources allows to control the pore size of the resulting carbon materials at the Ångstrom-level.

Abstract Electric double‐layer capacitors (EDLCs) that store electrical energy in the interface between an electrolyte and a solid electrode are favorable energy storage systems that demonstrate high‐power density, excellent cycle stability, and low environmental impact. To increase the operating voltage and improve the capacitance of EDLCs, it is essential to investigate the relationship between the degradation process and structural properties of activated carbon. In the current study, we used scanning electrochemical cell microscopy (SECCM) to assess the site‐specific degradation mechanisms caused by electrolyte decomposition. To simplify the structural properties of activated carbon, we used the highly oriented pyrolytic graphite (HOPG) as a model substrate to distinguish the edge and the basal planes of activated carbon. The mobile and nanoscale electrochemical cell provides local cyclic voltammetry (CV) to examine the difference in the degradation process at the edge and basal planes of HOPG. SECCM's nanoscale electrochemical cell can suppress the impact of capacitive current and can therefore be used to clearly measure the current associated with degradation caused by electrolyte decomposition. SECCM's local CV measurements directly exposed the degradation reaction that occurred at the edge plane in the positive potential range.

Conventional cooling systems rely on environmentally harmful halocarbons, while alternatives based on solid–solid transitions do not reach the required performance. Here the authors demonstrate using water and alcohol as refrigerants, through their confinement in nanosponges and their release by mechanical pressure.

Carbon-based materials are promising alternatives to noble metal catalysts, but their structures are typically disordered and difficult to control. Here, the authors obtain ordered carbonaceous frameworks with advantageous electrocatalytic properties via the carbonization of nickel-containing porphyrin dimer networks.

Schwarzites have a three-dimensional sp2 carbon structure with negative Gaussian curvatures. They can be synthesized through the deposition of carbon by chemical vapor deposition on a zeolite template and may be formed by increasing the amount of carbon. In this research, the amount of carbon deposition was increased by shortening the length of the diffusion pathways of the template through the use of nano-sized zeolite Y (nano-FAU). It was found that significantly larger quantities of carbon could be deposited inside the pores of nano-FAU (40 nm), compared to the micro-sized zeolite Y (300 nm). It is thus confirmed that by shortening the diffusion pathways enables more carbon to infiltrate into the center of the template before the pore channels are blocked, which leads to larger carbon depositions. A low acetylene gas concentration (15% vol in N2) and a prolonged period for chemical vapor deposition (6 h) is preferable for effectively loading carbon into the template. The obtained carbon replica exhibits the ordered structure derived from zeolite Y with an unprecedented 72 carbon atoms per supercage, of which a model with a structure similar to schwarzite was proposed.

A sensor chip that can detect enzyme electrode reactions with a sample volume as small as 20 μL has been developed using screen-printing technology with porous silica spheres (PSSs). PSSs are spherical particles of silica with mesoporous pores, a material with a large specific surface area. Other material properties of PSSs include good dispersibility, high mechanical strength, and the ability to be synthesized with precisely controlled mesopore sizes. These advantages support the increased adsorption of enzymes to create highly sensitive sensors. The electrode was designed as follows: carbon paste (CP) with PSSs was used as the working electrode, glucose dehydrogenase (GDH) was used as the enzyme, and quinoline-5,8-dione (QD) was used as the mediator of electron transfer to induce a glucose dehydrogenation reaction. The sensitivity of the sensor was demonstrated through the detection of glucose. The glucose sensor showed reliable sensitivity between 1 and 60 mM glucose, which is comparable to the detection range of a traditional working electrode such as platinum. Furthermore, the GDH had a minimal reduction in activity over repeated usage. This device demonstrates the ability to create an equally sensitive but less expensive and reusable sensor that has the potential to better suit general applications. [ABSTRACT FROM AUTHOR]

Abstract Lithium‐sulfur (Li‐S) batteries are considered as one of the most promising energy storage systems for next‐generation electric vehicles because of their high‐energy density. However, the poor cyclic stability, especially at a high sulfur loading, is the major obstacles retarding their practical use. Inspired by the nacre structure of an abalone, a similar configuration consisting of layered carbon nanotube (CNT) matrix and compactly embedded sulfur is designed as the cathode for Li‐S batteries, which are realized by a well‐designed unidirectional freeze‐drying approach. The compact and lamellar configuration with closely contacted neighboring CNT layers and the strong interaction between the highly conductive network and polysulfides have realized a high sulfur loading with significantly restrained polysulfide shuttling, resulting in a superior cyclic stability and an excellent rate performance for the produced Li‐S batteries. Typically, with a sulfur loading of 5 mg cm−2, the assembled batteries demonstrate discharge capacities of 1236 mAh g−1 at 0.1 C, 498 mAh g−1 at 2 C and moreover, when the sulfur loading is further increased to 10 mg cm−2 coupling with a carbon‐coated separator, a superhigh areal capacity of 11.0 mAh cm−2 is achieved.

One of the challenging targets in materials synthesis is a direct conversion of molecular based crystalline substances into crystalline ordered carbonaceous frameworks (OCFs). Though we have discovered the first example of the direct conversion with Ni-cyclic porphyrin dimer bridged by diacetylene moieties, such dimer requires a multi-step synthesis procedure with low yield and the resulting OCFs are not highly porous. Herein, we report the direct conversion of Ni-porphyrin monomer with ethynyl groups into OCF with developed microporosity. Upon heat-treatment, Ni-porphyrin monomer is thermally polymerized via ethynyl groups and the resulting polymer is successively converted into OCF at 873 K. Thus, ordered microporous material with conductive carbonaceous framework is obtained. The porphyrin Ni-N4 coordination structure is well retained after the carbonization and the microporous OCF exhibits specific electrocatalysis for CO2 conversion into CO with high selectivity. [ABSTRACT FROM AUTHOR]

We have fabricated Si nanopowder from Si swarf using the simple ball milling method, and applied to Li-ion battery electrodes. Limitation of the delithiation capacity after deep lithiation at 0.01 V is the most effective to achieve a constant high capacity for long cycles. The delithiation capacity keeps constant at 1500 mAh/g until the 290th cycle, and it slightly decreases to 1480 mAh/g at the 300th cycle. However, without limitation of the lithiation and delithiation capacities in the voltage range between 1.5 and 0.01 V, the delithiation capacity monotonically decreases with the cycle number, and it becomes 950 mAh/g at the 300th cycle. With limitation of the lithiation capacity at 1500 mAh/g after deep delithiation at 1.5 V, the delithiation capacity keeps 1470 mAh/g until the 137th cycle, and then decreases monotonically with the cycles to 860 mAh/g at the 300th cycle. With limitation of the delithiation capacity, the overvoltage estimated from the lithiation and delithiation curves is the lowest, and peeling-off of Si nanopowder from the Si electrode is suppressed because of limited size changes of Si nanopowder during lithiation and delithiation of Si nanopowder. [ABSTRACT FROM AUTHOR]

Asmall volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm23, 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm-3, which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs [ABSTRACT FROM AUTHOR]

A mesoporous silica film (MSF, 20 × 20 mm in size) with 3D accessible mesopores (Fmmmsymmetry) was synthesized on a current collector substrate, and then the entire pore surface was coated with an extremely thin carbon layer. The resulting carbon-coated mesoporous silica film (C/MSF), which well retains the continuous silica phase with its ordered mesopore network intact, has many advantages over conventional MSFs, porous carbons, or carbon electrodes. Thanks to the continuous carbon-coated layer, C/MSF is electrically conductive, and besides, it has remarkably better stability in an aqueous solution than MSFs. These features enable C/MSF to be used as a stable electrode in aqueous electrolyte solutions. In addition, C/MSF exhibits a much higher rate of performance as an electrode of an electric double layer capacitor than conventional powdery electrodes, indicating that the C/MSF electrode has excellent electrical conductivity, which can be ascribed to the continuous film shape of C/MSF. Another noticeable feature of C/MSF is light transmittance (67.9% at a wavelength of 1000 nm). Thus, C/MSF can be a transparent porous electrode unlike any porous carbon electrodes ever reported. Furthermore, due to the uniform mesopores (2 nm in diameter), C/MSF showed a large capability of immobilizing a giant active species such as iron-porphyrin molecules. Indeed, a much larger current was detected for the charge transfer from C/MSF to the iron-porphyrin than in the case of the iron-porphyrin loaded on a conventional graphite electrode. C/MSF is therefore a promising candidate as an effective electrode in various fields. [ABSTRACT FROM AUTHOR]

Abstract  We have measured the vapor pressure of 4He adsorbed in zeolite templated carbon (ZTC) at 4.2 K, in order to examine 4He film growth in the nanopore. ZTC has a framework made of non-stacked graphene, and has a relatively uniform 1.2 nm pore with three-dimensional (3D) periodicity of 1.4 nm. The nanoporous substrate is a candidate to realize superfluid 4He film with closer 3D connectivity than those studied so far. From the vapor pressure, coverage dependences of the thickness and the two-dimensional (2D) isothermal compressibility of 4He film were derived using thermodynamic equations. The 2D compressibility indicates the onset coverage n 1 of the second adsorption layer around 20 µmol/m2. It is confirmed that the 4He film in the 1.2 nm pores grows uniformly at least up to 1.3–1.5 n 1. [ABSTRACT FROM AUTHOR]

We succeeded in synthesizing edge-brominated zeolitetemplated carbon (ZTC-Br) as the key intermediate of edgefunctionalization of ZTC via an electrophilic aromatic substitution reaction using dibromoisocyanuric acid. ZTC-Br was easily converted into carbazole-modified ZTC (ZTC-Cz) using SuzukiMiyaura coupling. Interestingly, solvent-dependent changes of the fluorescence intensity of ZTC-Cz owing to its swellingshrinking behavior were observed. [ABSTRACT FROM AUTHOR]

Anodic aluminum oxide (AAO) with uniform straight nanochannels was completely coated with pure, N-doped, or B-doped carbon layer. Their electric double layer capacitances are measured in aqueous (1 M sulfuric acid) and organic (1 M Et4NBF4/polypropylene carbonate) electrolyte solutions in order to investigate the capacitance enhancement mechanisms caused by N- or B-doping. Since the three types of carbon-coated AAOs (pure, N-doped, or B-doped) have exactly the same pore structure, the observed capacitance enhancement was ascribable to only the following factors: (i) better wettability, (ii) the decrease of equivalent series resistance, (iii) the contribution of space-charge-layer capacitance, and (iv) the occurrence of pseudocapacitance. From the measurements of the wettability and the electrical resistance of the coated AAOs together with the electrochemical investigation (the cyclic voltammetry, the galvanostatic charge/discharge cycling, and the impedance analysis), it is concluded that the pseudocapacitance through faradic charge transfer (factor iv) is the most important factor to enhance the capacitance by N- or B-doping. This can be applied to not only the present carbon-coated AAOs but also any other porous carbons. [ABSTRACT FROM AUTHOR]

An attempt was made to synthesize a large-size silica porous monolith with straight and parallel nanochannels using an ice-rod nanoarray as a template. Since the previously reported ice templating methods allowed only the formation of micrometer-sized channels, special efforts were made to decrease the channel size down to the nanometer scale. Furthermore, such nanoporous silica monoliths were prepared not from an often-used and unstable hydrogel but from a stable colloidal silica solution. By increasing both the ice growing rate and the temperature gradient in the ice–water interface as much as possible, the channel size was reduced to 530 nm. Moreover, with the addition of the water-soluble polymers such as γ-cyclodextrin and dextran, the channel size was further decreased. Finally, using dextran polymer, the channel size reached as small as 180 nm, which is close to the theoretical lower limit (120 nm) in the present silica solution. This noticeable effect of the polymers may be explained from their strong interaction with water molecules through hydrogen bonding, but the most necessary condition for the polymers is that they never induce the aggregation of the silica particles in the solution. The methodology of obtaining much narrower channels using the ice templating method was discussed on the basis of the present results. [ABSTRACT FROM AUTHOR]

Zeolite-templated carbon (ZTC) was utilized to prepare Pt nanoparticles as a support by using a simple impregnation method. The choice of a cationic Pt precursor led to the formation of highly and uniformly dispersed Pt nanoparticles on ZTC, which afforded high conversion in the catalytic hydrogenation of phenylacetylene. [ABSTRACT FROM AUTHOR]