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While the functions of carbon materials with precisely controlled nanostructures have been reported in many studies, their chiral discriminating abilities have not been reported yet. Herein, chiral discrimination is achieved using helical carbon materials devoid of chiral attachments. A Fe

Carbon materials with 3D-ordered nanopores doped with metals and nitrogen were synthesized from strategically designed phthalocyanines via the self-assembly of Fe3O4 nanoparticles. Their catalytic activity was determined by the doped metals.

The applicability of chitin-based carbon as a supercapacitor electrode material was investigated by adjusting its pore structure through polystyrene latex templating, without significant N doping. 2,2,6,6-tetramethylpiperidinyloxy (TEMPO)-oxidized chitin nanofibers were mixed with polystyrene latex, hydrothermally treated at 220 °C, carbonized, and activated using KOH at 800 °C, yielding activated hierarchical porous carbon. The variation of both polystyrene latex amount and carbonization temperature resulted in changes in the surface area and pore structure, which dictated the degree of pore uniformity and activation efficiency. The pore structure affected activation by allowing the selective removal of amorphous carbon, exposing the basal plane carbon, resulting in higher specific capacitance. By making activated hierarchical porous carbon more conducive to activation, specific capacitance of 567 F g

Iron-incorporated ordered carbonaceous frameworks (OCFs) have been synthesized by the pyrolysis of iron porphyrin with ethynyl groups as polymerizable/carbonizable moieties at a temperature higher than 600 °C. The pyrolysis behavior is analyzed by thermogravimetry-differential thermal analysis-mass spectrometry, and the obtained carbon materials are characterized by X-ray diffraction, X-ray absorption fine structure, and high-angle annular dark-field scanning transmission electron microscopy. The introduction of ethynyl groups at the meta positions of the peripheral phenyl groups is essential for efficient cross-linking upon thermal polymerization. The thermally stable polymer thus obtained can be transformed into OCFs with high carbonization yield of 93 % at the subsequent carbonization. OCFs possess periodic structural regularity and porphyrin Fe-N4 coordination structure, and exhibit electrocatalysis for the conversion of CO2 into CO.

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 discov...

Low-dimensional high-entropy materials, such as nanoparticles and two-dimensional (2D) layers, have great potential for catalysis and energy applications. However, it is still challenging to synthesize 2D layered high-entropy materials through a bottom-up soft chemistry method, due to the difficulty of mixing and assembling multiple elements in 2D layers. Here, we report a simple polyol process for the synthesis of a series of 2D layered high-entropy transition metal (Co, Cr, Fe, Mn, Ni, and Zn) hydroxides (HEHs), involving the hydrolysis and inorganic polymerization of metal-containing species in ethylene glycol media. The as-synthesized HEHs demonstrate 2D layered structures with interlayer distances ranging from 0.860 to 0.987 nm and homogeneous elemental distribution of designed equimolar stoichiometry in the layers. These 2D HEHs exhibit a low overpotential of 275 mV at 10 mA cm

Force-responsive ordered carbonaceous frameworks (OCFs) are synthesized for the first time. Carbonization of Ni porphyrin monomers having eight polymerizable ethynyl groups yields OCFs with atomically dispersed divalent Ni species and developed micropores. The highest specific surface area (673 m2 g−1) among the OCFs has been achieved. The OCFs thus synthesized comprise non-stacked graphene sheets, affording a unique mechanical flexibility that enables force-driven reversible phase transition.

An indirect fuel cell system is constructed. The system is composed of a redox flow battery (RFB) to extract electrical energy and two chemical reactors (anolyte and catholyte regenerators). A quinone as a redox mediator is reduced by a mixture of hydrogen and carbon monoxide in the anolyte regenerator, whereas a polyoxometalate as another redox mediator is oxidized in the catholyte regenerator, followed by a steady-state power generation at the RFB using the two redox mediators as active materials. This system demonstrates how to reduce the amount of platinum required in a proton-exchange membrane fuel cell (PEMFC), especially when using a fuel other than pure hydrogen. The RFB in our system contains two gas-diffusion electrodes (GDEs) with a platinum electrocatalyst to insert a “pure hydrogen gas phase” between the anolyte and catholyte to avoid cross-contamination. These two GDEs participate in the hydrogen evolution reaction and hydrogen oxidation reaction, respectively, and require only a small amount of platinum. In addition, the catalysts used in the anolyte regenerator are rhodium complexes. However, these catalysts are in a dissolved state (molecular catalysts) with micromolar-order concentrations, and very little noble metal is used. A carbonaceous catalyst without platinum is used in the catholyte regenerator. This eliminates the need for a noble metal for the oxygen reduction reaction, which is the main reason why platinum is used in a large amount in a conventional PEMFC. Steady-state operations of the anode side, the cathode side, and the total system are demonstrated in this work. Although a small amount of noble metal is still required at this stage, this work may contribute to the complete elimination of noble metals from a PEMFC.

Polyacrylonitrile (PAN)-derived carbon beads with uniform size and high surface area were successfully prepared by the carbonization of PAN and activation by KOH. Physicochemical analysis revealed ...

Facile and efficient methods to prepare active electrodes for redox reactions of electrolyte ions are required to produce efficient and low-cost redox flow batteries (RFBs). Carbon-fiber electrodes are widely used in various types of RFBs and surface oxidation is commonly performed to enhance the redox reactions, although it is not necessarily efficient. Quite recently, a technique for nanoscale and uniform surface etching of the carbon fiber surface was developed and a significant enhancement of the negative electrode reaction of vanadium redox flow batteries was attained, although the enhancement was limited to the positive electrode reaction. In this study, we attempted to obtain an additional enhancement effect of metal-oxide nanoparticles without the need for further processing steps. A coating with carbonaceous thin films was obtained coating by sublimation, deposition, and pyrolysis of tin(II) phthalocyanine (SnPc) on a carbon fiber surface in a single heat-treatment step. The subsequent thermal oxidation concurrently achieved nanoscale surface etching and loading with SnO2 nanoparticles. The nanoscale-etched and SnO2-loaded surface was characterized by field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The activity for the vanadium ion redox reactions was evaluated by cyclic voltammetry (CV) to demonstrate the enhancement of both the positive and negative electrode reactions. A full cell test of the vanadium redox flow battery (VRFB) showed a significant decrease of the overpotential and a stable cycling performance. A facile and efficient technique based on the nanoscale processing of the carbon fiber surface was presented to substantially enhance the activity for the redox reactions in redox flow batteries.

Assembly of graphitized carbon nanowalls containing crystallites with the ideal interlayer distance was formed as a Voronoi cell structure of close-packed template nanoparticles. The assembly showed faster Li-ion intercalation and deintercalation than conventional graphite, a superhydrophobicity, which was retained even after thermal oxidation, and a high stability under electrochemical oxidative conditions.

Very fine Ni nanoparticles including subnanoclusters are dispersed in zeolite-templated carbon (ZTC), by thermal decomposition (573 K) of nickelocene pre-loaded on ZTC which functions as a high-surface area support. X-ray absorption fine structure reveals that the Ni species formed by the thermal decomposition is in a unique oxidized state. It is different from nickelocene, Ni metal, or any other inorganic Ni species. The unique Ni species can dissociatively adsorb H2, and enhance the following spillover even under ambient conditions. The spillover activity of the non-metallic Ni subnanoclusters is superior to that of Ni-metal nanoparticles and even comparable to that of Pt nanoparticles.

A metal-containing carbonaceous two-dimensional lattice was formed on a graphene plane by sublimation, deposition, and pyrolysis of Fe phthalocyanine (Pc). The formation and growth of the FePc-derived π-conjugated planar system were reflected by its orientation conversion from the perpendicular to horizontal mode and by the N K-edge X-ray absorption near-edge structure.

Activated carbon monolith (ACM) was obtained from Amygdalus pedunculata shell (APS) and polyacrylonitrile (PAN) via a template-free approach. APS was uniformly distributed into the monolith matrix and an interconnected network was fully established. The present study greatly promotes the close contact between desert reclamation and green energy storage.

Activated carbons, BC-PANnp-ACs and BC-PANnp-KACs, have been synthesized from a composite (BC-PANnp) derived from bacterial cellulose (BC) and polyacrylonitrile nanoparticles (PANnp) by physical and chemical activation, respectively. Commercially available nata de coco has been used as the source of BC whereas PAN nanoparticles of ca. 100 nm have been synthesized in situ in the BC gel by emulsion polymerization which covers the nanofibers of BC. FE-SEM images confirm that hierarchical lamellar structure of BC is retained in the activated carbon frameworks. Detailed electrochemical studies carried out with the electrodes designed with the activated carbons reveal their good performance as electric double layer capacitors (EDLC) with fast response and high-speed charging and discharging. The activated carbons prepared by KOH activation have much higher specific surface area and exhibit better electrochemical properties compared to the carbon materials obtained by CO2 activation or the commercially available YP50F activated carbon derived from coconut shell. The three-dimensional network structure peculiar to BC reduces the grain boundary resistance between the carbonized PAN nanoparticles in these composites compared to PAN nanoparticles carbonized alone imparting good conductivity without the addition of a conductive agent.

Surface treatments are often applied to carbon materials to impart specific functions to the surface. Surface oxidation is a typical treatment to form oxygen-containing surface functional groups on carbon fiber electrodes of redox flow batteries in order to enhance the performance, which has attracted much attention as a large-scale electric energy storage system. At present, however, little attention has been paid to the effect of the edge plane exposure. In this study, fine etching of the graphitized carbon fiber surface was attained by coating the surface with a metal-containing carbonaceous thin film and thermal oxidation. The etching was caused by the catalysis of the metal species; the mechanism and the effect of the carbonaceous film were demonstrated by in situ X-ray absorption fine structure measurements. The finely etched surface possessed substantially enriched edge planes and an enhanced activity for the positive and negative electrode reactions of the vanadium redox flow battery. The flow cel...

Nitrogen-doped porous monolithic carbon (NDPMC) is obtained from biomass-derived activated carbon/polyacrylonitrile composite for the first time via a template-free thermally induced phase separation (TIPS) approach followed by KOH activation. The electrochemical results indicate that NDPMC possesses ultrahigh specific capacitance of 442 F g−1 at 1 A g−1, excellent rate capability with 81% retention rate from 1 to 100 A g−1 and outstanding cycling stability with 98% capacitance retention at 20 A g−1 after 5000 cycles. Furthermore, the evaluation of NDPMC on the practical symmetrical system also exhibits desired electrochemical performances. The novel composite carbon displays remarkable capacitance properties and the feasible, low-cost synthetic route demonstrates great potential for large-scale production of high-performance electrode materials for supercapacitors.

Hierarchically porous activated carbons (ACs) derived from apricot shell (AS), which is a low-cost and abundant carbon source from a renewable and sustainable biomass waste, were prepared by a green and facile approach via carbonization followed by steam activation and applied to electrodes for symmetric supercapacitors (SCs). The as-obtained AC possessed large surface area and developed porosity with hierarchical pore texture, leading to the specific capacitance of 38.3 F g−1 for an AC//AC symmetrical SC in 20 wt% H2SO4 aqueous electrolyte. Moreover, the assembled AC//AC SC exhibited superior cycling life stability with 99% retention after 6000 cycles at 5 A g−1. These results demonstrate that the present facile, low-cost, and environmentally friendly synthetic strategy for hierarchical ACs from AS can promote the utilization and conversion of AS to high value-added industrial products as well as commercial applications in energy storage devices.

Despite recent advances in the carbonization of organic crystalline solids like metal-organic frameworks or supramolecular frameworks, it has been challenging to convert crystalline organic solids into ordered carbonaceous frameworks. Herein, we report a route to attaining such ordered frameworks via the carbonization of an organic crystal of a Ni-containing cyclic porphyrin dimer (Ni2-CPDPy). This dimer comprises two Ni–porphyrins linked by two butadiyne (diacetylene) moieties through phenyl groups. The Ni2-CPDPy crystal is thermally converted into a crystalline covalent-organic framework at 581 K and is further converted into ordered carbonaceous frameworks equipped with electrical conductivity by subsequent carbonization at 873–1073 K. In addition, the porphyrin’s Ni–N4 unit is also well retained and embedded in the final framework. The resulting ordered carbonaceous frameworks exhibit an intermediate structure, between organic-based frameworks and carbon materials, with advantageous electrocatalysis. This principle enables the chemical molecular-level structural design of three-dimensional carbonaceous frameworks., 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.

N-doped porous monolithic carbons (PMC) have been developed from polyacrylonitrile (PAN) via a template-free thermally induced phase separation (TIPS) approach followed by an easy pyrolysis process. Three-dimensional (3D) PAN monolith (PM) was firstly fabricated as the starting material. The shape of the 3D PM was designed during the phase separation step, revealing that the product carbons had the potential advantages of desired porosity and controllable shape. Two typical activation methods were employed and compared to prepare PMC. KOH-activated PMC showed a larger surface area of 1600 m2 g−1 and higher nitrogen content of 5.6% in comparison to that being activated in a carbon dioxide atmosphere (CD-PMC). The electrochemical measurements revealed that PMC possessed a high capacitance of 270 F g−1 at 0.2 A g−1 and 195 F g−1 even at 100 A g−1, ultra-high rate capability with 72% capacitance retention from 0.2 to 100 A g−1 and outstanding cycling stability with 100% capacitance retention at 20 A g−1 after 5000 cycles. These results demonstrate that the present facile and efficient synthetic strategy for PMC from PAN can benefit the promotion of its application in energy storage devices and it is highly likely to be extended to other polymer sources.

Interest in chiral substances has mainly focused on the substances themselves, but not on the accompanying space, especially regarding the pore alignment. As a method to form both the chiral substance and the accompanying space, cylindrical self-assembly of uniform polystyrene nanoparticles with fructose is carried out in the presence of both carbon and sodium alginate, which is followed by heat treatment in an inert atmosphere. The carbonization generates fructose-derived honeycomb-like carbon walls with helically aligned nanopores left after the polystyrene decomposition. The diffuse reflectance circular dichroism measurements give peaks with opposite signs for the d- and l-fructose-derived cylindrical carbons. Circularly polarized light sensitivity in transient photoconductivity is confirmed apparently in the carbon-based helical structures. This sensitivity as well as straightforward formation of composites with another component to give helicity shows potential applications of the helically aligned pores.

Bifunctional catalysts for oxygen reduction and evolution reactions are essential components of zinc–air batteries (ZABs) for the air electrode. Carbonaceous materials have been investigated as these catalysts since the early stage of ZAB research. Recent studies have revealed promising carbonaceous materials with heteroatoms and transition metals doped into the surface or incorporated as nanoparticles, although the activity still needs improvement. In this study, the double coating of carbonaceous thin film containing Fe and N on a graphitic carbon fiber surface was performed via sublimation, deposition, and pyrolysis of iron phthalocyanine (FePc). In the first coating, the thin film and Fe nano-aggregates on the surface were generated, which were encapsulated in the carbonaceous shell to generate protrusions in the second coating. The presence of the protrusion enhanced the oxygen reduction activity. Such protrusion was also formed by the single coating with a sufficient FePc feed; however, the activity enhancement was limited. Contrarily, the double coating considerably enhanced the activity and surpassed that of Pt in the high potential region. In addition, the oxygen evolution reaction was improved by the FePc-derived thin film coating. The durability was confirmed by the stable cycling performance of ZAB with the double-coated electrode.

Enhancement of the electrode reactions in vanadium redox flow batteries is highly demanded for improvement of their efficiency. In a recent study, the catalytic activity for the positive electrode discharge reaction was found at a carbonaceous material with an active site consisting of iron coordinated by 4 nitrogens in the square-planar configuration and embedded on the surface. The catalyst was formed as a thin film on the surface of a cup-stack carbon nanotube. In this study, the improvement of the structure of the catalyst layer consisting of the catalyst and ion-exchange polymer as a binder was attempted in order to enhance the positive electrode reactions. The catalyst layer structure was changed in two ways; variation in the binder content and inclusion of magnesium oxide in the catalyst layer as a pore-forming agent. The lower binder content produced a thinner coating on the catalyst, which was favorable for enhancement of the mass transfer in the layer, although the lack of the binder caused an insufficient dispersion of the catalyst in the layer, thus lowering the activity. The pores left after the removal of the magnesium oxide in the layer was also favorable for the mass transfer and effective for the electrode reaction enhancement unless an excessive amount of magnesium oxide was added to generate disorder in the layer.

It has been found that carbonaceous materials containing a transition metal coordinated by 4 nitrogens in the square-planar configuration (metal–N4 site) on the surface possessed a catalytic activity for various electrochemical reactions related to energy conversion and storage; i.e., oxygen reduction, hydrogen evolution, and quite recently, the electrode reactions in vanadium redox flow batteries (VRFB). The catalyst for the VRFB positive electrode discharge reaction, i.e., the dioxovanadium ion reduction, was formed by coating the surface of cup-stack carbon nanotubes with a carbonaceous thin film with the Fe–N4 site generated by the sublimation, deposition, and pyrolysis of iron phthalocyanine. In this study, the influence of the physical properties of the catalyst on the electrochemical reactions was investigated to optimize the coating. With an increase in the coating, the specific surface area increased, whereas the pore size decreased. The surface Fe concentration was increased in spite of the Fe aggregation inside the carbon matrix. The catalytic activity enhancement was achieved due to the increase in the specific surface area and the surface Fe concentration, but was lowered due to the decrease in the pore size, which was disadvantageous for the penetration of the electrolyte and the mass transfer.

A metal-containing carbonaceous two-dimensional lattice was formed on a graphene plane by sublimation, deposition, and pyrolysis of Fe phthalocyanine (Pc). The formation and growth of the FePc-derived π-conjugated planar system were reflected by its orientation conversion from the perpendicular to horizontal mode and by the N K-edge X-ray absorption near-edge structure.