Controlled Synthesis of N-Doped Carbon Nanospheres with Tailored Mesopores through Self-Assembly of Colloidal Silica

Asymmetric Microenvironment Tailoring Strategies of Atomically Dispersed Dual-Site Catalysts for Oxygen Reduction and CO2 Reduction Reactions

Dual-atom catalysts (DACs) with atomically dispersed dual-sites, as an extension of single-atom catalysts (SACs), have recently become a new hot topic in heterogeneous catalysis due to their maximized atom efficiency and dual-site diverse synergy, because the synergistic diversity of dual-sites achieved by asymmetric microenvironment tailoring can efficiently boost the catalytic activity by optimizing the electronic structure of DACs. Here, this work first summarizes the frequently-used experimental synthesis and characterization methods of DACs. Then, four synergistic catalytic mechanisms (cascade mechanism, assistance mechanism, co-adsorption mechanism and bifunction mechanism) and four key modulating methods (active site asymmetric strategy, transverse/axial-modification engineering, distance engineering and strain engineering) are elaborated comprehensively. The emphasis is placed on the effects of asymmetric microenvironment of DACs on oxygen/carbon dioxide reduction reaction. Finally, some perspectives and outlooks are also addressed. In short, the review summarizes a useful asymmetric microenvironment tailoring strategy to speed up synthesis of high-performance electrocatalysts for different reactions.

A dual-template synergistic assembly strategy towards the synthesis of extra-small nitrogen-doped mesoporous carbon nanospheres with large pores

Functional mesoporous carbon nanomaterials with large pores and small particle sizes have broad accessibility, but remain challenging to achieve. This study proposed a dual-template synergistic assembly strategy to facilely synthesize extra-small nitrogen-doped mesoporous carbon nanospheres with large pores in a low-cost manner. Directed by the synergistic effect of the combination of surfactants, sodium oleate (anionic surfactant) and triblock copolymer-P123 (nonionic surfactant) were selected as templates to construct nanomicelles (nanoemulsions), which were co-assembled with melamine-based oligomers to form composite nanomicelles, thus obtaining nitrogen-doped mesoporous polymer nanospheres (NMePS) and then nitrogen-doped mesoporous carbon nanospheres (NMeCS). Based on Schiff base chemistry, the melamine-based oligomers with self-assembly capability were synthesized as precursors, which is different from the conventional synthetic route of melamine-formaldehyde resin. The key parameters involved in the route were investigated comprehensively and correlated with the characterization results. Furthermore, the 50 nm-scale particle size and the large mesoporous size of 5.5 nm of NMeCS can facilitate effective mass transport, coupled with their high nitrogen content (15.7 wt%), contributing to their excellent performance in lithium-ion batteries.

2D Covalent Organic Framework Covalently Anchored with Carbon Nanotube as High-Performance Cathodes for Lithium and Sodium-Ion Batteries

Covalent organic frameworks (COFs), featuring structural diversity, permanent porosity, and functional versatility, have emerged as promising electrode materials for rechargeable batteries. To date, amorphous polymer, COF, or their composites are mostly explored in lithium-ion batteries (LIBs), while their research in other alkali metal ion batteries is still in infancy. This can be due to the challenges that arise from large volume changes, slow diffusion kinetics, and inefficient active site utilization by the large Na+ or K+ ion. Herein, microwave-assisted imide-based 2D COF, TAPB-NDA covalently connected with amine-functionalized carbon nanotubes (TAPB-NDA@CNT) targeting the application in both Li-/Na-ion batteries, is synthesized. As-synthesized, TAPB-NDA@CNT50 displays the good performance as LIB cathode with a specific capacity of ≈138 mAh g-1 at 25 mA g-1, long cycling stability (81.2% retention after 2000 cycles at 300 mA g-1), with excellent reversible capacity retention of ≈79.6%. Similarly, TAPB-NDA@CNT50, when employed in sodium-ion battery (SIB), exhibited 136.7 mAh g-1 specific capacity at 25 mA g-1, retained ≈80% of the reversible capacity after 1000 cycles at 300 mA g-1 and showing excellent rate performance. The structural advantage of TAPB-NDA@CNT will encourage researchers to design COF-based cathodes for the alkali ion batteries.

A General Strategy Based on Hetero-Charge Coupling Effect for Constructing Single-Atom Sites

Single-atom catalysts have emerged as cutting-edge hotspots in the field of material science owing to their excellent catalytic performance brought about by well-defined metal single-atom sites (M SASs). However, huge challenges still lie in achieving the rational design and precise synthesis of M SASs. Herein, we report a novel synthesis strategy based on the hetero-charge coupling effect (HCCE) to prepare M SASs loaded on N and S co-doped porous carbon (M1/NSC). The proposed strategy was widely applied to prepare 17 types of M1/NSC composed of single or multi-metal with the integrated regulation of the coordination environment and electronic structure, exhibiting good universality and flexible adjustability. Furthermore, this strategy provided a low-cost method of efficiently synthesizing M1/NSC with high yields, that can produce more than 50 g catalyst at one time, which is key to large-scale production. Among various as-prepared unary M1/NSC (M can be Fe, Co, Ni, V, Cr, Mn, Mo, Pd, W, Re, Ir, Pt, or Bi) catalysts, Fe1/NSC delivered excellent performance for electrocatalytic nitrate reduction to NH3 with high NH3 Faradaic efficiency of 86.6 % and high NH3 yield rate of 1.50 mg h-1 mgcat. -1 at -0.6 V vs. RHE. Even using Fe1/NSC as a cathode in a Zn-nitrate battery, it exhibited a high open circuit voltage of 1.756 V and high energy density of 4.42 mW cm-2 with good cycling stability.

Constructing Nano-Heterostructure with Dual-Site to Boost H2O2 Activation and Regulate the Transformation of Free Radicals

A major issue with Fenton-like reaction is the excessive consumption of H2O2 caused by the sluggish regeneration rate of low-valent metal, and how to improve the activation efficiency of H2O2 has become a key in current research. Herein, a nano-heterostructure catalyst (1.0-MnCu/C) based on nano-interface engineering is constructed by supporting Cu and MnO on carbon skeleton, and its kinetic rate for the degradation of tetracycline hydrochloride is 0.0436 min-1, which is 2.9 times higher than that of Cu/C system (0.0151 min-1). The enhancement of removal rate results from the introduced Mn species can aggregate and transfer electrons to Cu sites through the electron bridge Mn-N/O-Cu, thus preventing Cu2+ from oxidizing H2O2 to form O2 •-, and facilitating the reduction of Cu2+ and generating more reactive oxygen species (1O2 and ·OH) with stronger oxidation ability, resulting in H2O2 utilization efficiency is 1.9 times as much as that of Cu/C. Additionally, the good and stable practical application capacity in different bodies demonstrates that it has great potential for practical environmental remediation.

Surface-Pore-Modified N-Doped Amorphous Carbon Nanospheres Tailored with Toluene as Anode Materials for Lithium-Ion Batteries

The surface modification of amorphous carbon nanospheres (ACNs) through templates has attracted great attention due to its great success in improving the electrochemical properties of lithium storage materials. Herein, a safe methodology with toluene as a soft template is employed to tailor the nanostructure, resulting in ACNs with tunable surface pores. Extensive characterizations through transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption isotherms elucidate the impact of surface pore modifications on the external structure, morphology, and surface area. Electrochemical assessments reveal the enhanced performance of the surface-pore-modified carbon nanospheres, particularly ACNs-100 synthesized with the addition of 100 μL toluene, in terms of the initial discharge capacity, rate performance, and cycling stability. The interesting phenomenon of persistent capacity increase is ascribed to lithium ion movement within the graphite-like interlayer, resulting in ACNs-100 experiencing a capacity upswing from an initial 320 mAh g-1 to a zenith of 655 mAh g-1 over a thousand cycles at a rate of 2 C. The findings in this study highlight the pivotal role of tailored nanostructure engineering in optimizing energy storage materials.

Bionic Fe-N-C catalyst with abundant exposed Fe-Nx sites and enhanced mass transfer properties for efficient oxygen reduction

Transition metal and nitrogen co-doped carbon electrocatalysts are promising candidates to replace the precious metal platinum (Pt) in oxygen reduction reactions (ORR). Unfortunately, the electrochemical performance of existing electrocatalysts is restricted due to limited accessibility of active sites. Inspired by jellyfish tentacles, we design an efficient ORR micro-reactor called Fe-Nx/HC@NWs. It features abundant exposed Fe-Nx active sites dispersed on nitrogen-doped cubic carbon cages, which have a hierarchically porous and hairy structure. The accessible, atomically dispersed Fe-Nx sites and the elaborate substrate architecture synergize to provide the catalyst withremarkable ORR catalytic activity, extraordinary long-term stability, and favorable methanol tolerance in an alkaline electrolyte; overall, its performance is comparable to that of commercial carbon-supported Pt. Our synthesis is facile and controllable, paving a new avenue toward advanced non-precious metal-based electrocatalysts for energy storage and conversion.

Synthesis of multi-cavity mesoporous carbon nanospheres through solvent-induced self-assembly: Anode material for sodium-ion batteries with long-term cycle stability

Mesoporous carbon nanospheres (MCSs) are extensively employed in energy storage applications due to their ordered pore size, large specific surface area (SSA), and abundant active sites, resulting in excellent electrochemical performance for sodium storage. However, challenges persist in achieving precise structural control and stable synthesis reactions for these MCSs. Additionally, employing MCSs with a larger SSA in sodium storage applications can lead to increased side reactions and potential structural instability. To address these issues, we propose a solvent-induced self-assembly method for obtaining high nitrogen-containing multi-cavity MCSs with reduced SSA. The morphology and SSA of the nanospheres can be precisely adjusted by regulating the reaction time. Introducing an amine-phenol bridging structure into the polymer system significantly bolsters the structural and morphological stability of the mesoporous materials. The performance of these novel nanospheres in sodium-ion batteries (SIBs) is remarkable, exhibiting excellent sodium storage capability and exceptional ultra-long cycle stability. At a rate of 0.1 A g-1, the nanospheres achieved a high reversible capacity of 252 mAh g-1, and even after 20,000 cycles at 5 A g-1, a specific capacity of 136 mAh g-1 was retained. In summary, our study presents a novel approach for synthesizing mesoporous carbon materials and offers valuable insights for sodium storage research, opening new possibilities for enhancing energy storage applications.

Tailored Porous Carbon Xerogels for Fe-N-C Catalysts in Proton Exchange Membrane Fuel Cells

Atomically dispersed Fe-N-C catalysts for the oxygen reduction reaction (ORR) have been synthesized with a template-free method using carbon xerogels (CXG) as a porous matrix. The porosity of the CXGs is easily tunable through slight variations in the synthesis procedure. In this work, CXGs are prepared by formaldehyde and resorcinol polymerization, modifying the pH during the process. Materials with a broad range of porous structures are obtained: from non-porous to micro-/meso-/macroporous materials. The porous properties of CXG have a direct effect on Fe-N-CXG activity against ORR in an acidic medium (0.5 M H2SO4). Macropores and wide mesopores are vital to favor the mass transport of reagents to the active sites available in the micropores, while narrower mesopores can generate additional tortuosity. The role of microporosity is investigated by comparing two Fe-N-C catalysts using the same CXG as the matrix but following a different Fe and N doping procedure. In one case, the carbonization of CXG occurs rapidly and simultaneously with Fe and N doping, whereas in the other case it proceeds slowly, under controlled conditions and before the doping process, resulting in the formation of more micropores and active sites and achieving higher activity in a three-electrode cell and a better durability during fuel cell measurements. This work proves the feasibility of the template-free method using CXG as a carbon matrix for Fe-N-C catalysts, with the novelty of the controlled porous properties of the carbon material and its effect on the catalytic activity of the Fe-N-C catalyst. Moreover, the results obtained highlight the importance of the carbon matrix's porous structure in influencing the activity of Fe-N-C catalysts against ORR.

One-Dimensional Covalent Organic Framework as High-Performance Cathode Materials for Lithium-Ion Batteries

Covalent organic frameworks (COFs) have emerged as a new class of cathode materials for energy storage in recent years. However, they are limited to two-dimensional (2D) or three-dimensional (3D) framework structures. Herein, this work reports designed synthesis of a redox-active one-dimensional (1D) COF and its composites with 1D carbon nanotubes (CNTs) via in situ growth. Used as cathode materials for Li-ion batteries, the 1D COF@CNT composites with unique dendritic core-shell structure can provide abundant and easily accessible redox-active sites, which contribute to improve diffusion rate of lithium ions and the corresponding specific capacity. This synergistic structural design enables excellent electrochemical performance of the cathodes, giving rise to 95% utilization of redox-active sites, high rate capability (81% capacity retention at 10 C), and long cycling stability (86% retention after 600 cycles at 5 C). As the first example to explore the application of 1D COFs in the field of energy storage, this study demonstrates the great potential of this novel type of linear crystalline porous polymers in battery technologies.

Synthesis of β-FeOOH/polyaniline heterogeneous catalyst for efficient photo-Fenton degradation of AOII dye

Discharge of the untreated dye-containing wastewaters will induce water source pollution and further harm aquatic organisms. In this study, the akaganéite/polyaniline catalyst (β-FeOOH/PANI, about 1.0 μm) could be successfully composed by polyaniline (PANI, (C₆H₇N)_n, 200-300 nm) and akaganéite (β-FeOOH, FeO(OH)_1-xCl_x, less than 200 nm), according to the identification and characterization results of XRD, Ramon, FTIR, XPS, SEAD, EDS, and FESEM (or HRTEM). Due to PANI providing more photogenerated electrons, the β-FeOOH/PANI composite (compared with β-FeOOH) in photo-Fenton system had the more highly catalytic degradation capacity to Acid Orange II (AOII) under an optimal condition (7.5 mmol/L of H₂O₂ oxidant, 40 mg/L of AOII, 0.2 g/L of catalyst dosage, and pH 4.0). The AOII degradation kinetics could be well fitted by pseudo-first-order model. In photo-Fenton catalytic process of AOII dye, the ∙OH and h⁺ were the main reaction substances. The AOII in solutions could be gradually mineralized into non-toxic inorganic H₂O molecule and CO₂. The β-FeOOH/PANI catalyst also had a good reusable ability of about 91.4% AOII degradation after 4 runs. These results can provide a reference for synthesis of catalyst used in photo-Fenton system and the applications in degradation removal of organic dye from wastewaters.

Carbon nanosphere synthesis and applications for rechargeable batteries

Carbon nanospheres (CNSs) have attracted great interest in energy conversion and storage technologies due to their excellent chemical and thermal stability, high electrical conductivity and controllable size structure characteristics. In order to further improve the energy storage properties, many efforts have been made to design suitable nanocarbon spherical materials to improve electrochemical performance. In this overview, we summarize the recent research progress on CNSs, mainly focusing on the synthesis methods and their application as high-performance electrode materials in rechargeable batteries. As for the synthesis methods, hard template methods, soft template methods, the extension of the Stöber method, hydrothermal carbonization, aerosol-assisted synthesis are described in detail. In addition, the use of CNSs as electrodes in energy storage devices (mainly concentrated on lithium-ion batteries (LIBs)), sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are also discussed in detail in this article. Finally, some perspectives on the future research and development of CNSs are provided.

A Versatile 3D-Confined Self-Assembly Strategy for Anisotropic and Ordered Mesoporous Carbon Microparticles

Mesoporous carbon microparticles (MCMPs) with anisotropic shapes and ordered structures are attractive materials that remain challenging to access. In this study, a facile yet versatile route is developed to prepare anisotropic MCMPs by combining neutral interface-guided 3D confined self-assembly (3D-CSA) of block copolymer (BCP) with a self-templated direct carbonization strategy. This route enables pre-engineering BCP into microparticles with oblate shape and hexagonal packing cylindrical mesostructures, followed by selective crosslinking and decorating of their continuous phase with functional species (such as platinum nanoparticles, Pt NPs) via in situ growth. To realize uniform in situ growth, a "guest exchange" strategy is proposed to make room for functional species and a pre-crosslinking strategy is developed to preserve the structural stability of preformed BCP microparticles during infiltration. Finally, Pt NP-loaded MCMPs are derived from the continuous phase of BCP microparticles through selective self-templated direct carbonization without using any external carbon source. This study introduces an effective concept to obtain functional species-loaded and N-doped MCMPs with oblate shape and almost hexagonal structure (p6mm), which would find important applications in fuel cells, separation, and heterogeneous catalysis.

Constructing Unique Mesoporous Carbon Superstructures via Monomicelle Interface Confined Assembly

Constructing hierarchical three-dimensional (3D) mesostructures with unique pore structure, controllable morphology, highly accessible surface area, and appealing functionality remains a great challenge in materials science. Here, we report a monomicelle interface confined assembly approach to fabricate an unprecedented type of 3D mesoporous N-doped carbon superstructure for the first time. In this hierarchical structure, a large hollow locates in the center (∼300 nm in diameter), and an ultrathin monolayer of spherical mesopores (∼22 nm) uniformly distributes on the hollow shells. Meanwhile, a small hole (4.0-4.5 nm) is also created on the interior surface of each small spherical mesopore, enabling the superstructure to be totally interconnected. Vitally, such interconnected porous supraparticles exhibit ultrahigh accessible surface area (685 m² g^-1) and good underwater aerophilicity due to the abundant spherical mesopores. Additionally, the number (70-150) of spherical mesopores, particle size (22 and 42 nm), and shell thickness (4.0-26 nm) of the supraparticles can all be accurately manipulated. Besides this spherical morphology, other configurations involving 3D hollow nanovesicles and 2D nanosheets were also obtained. Finally, we manifest the mesoporous carbon superstructure as an advanced electrocatalytic material with a half-wave potential of 0.82 V (vs RHE), equivalent to the value of the commercial Pt/C electrode, and notable durability for oxygen reduction reaction (ORR).

Competition among Refined Hollow Structures in Schiff Base Polymer Derived Carbon Microspheres

Synthetic polymer-derived hollow carbon spheres have great utilitarian value in many fields for which the synthesis of proper polymer precursors is a key process. The exploration of new suitable polymer precursors and the construction of refined hollow structures in emerging polymers are both of great significance for synthetic methodology and novel carbon materials. Here, for the first time Schiff base polymer (SBP) colloid spheres with refined hollow structures were synthesized by tandem gradient growth and confined polymerization processes. The Hill equation was employed as a mathematical model to explain the gradient growth of SBP spheres. The size-dependent inner structure of SBP spheres can be adjusted from hollow to multichamber-surrounded hollow, and then to a multichamber structure. SBP-derived carbon spheres having similar surface area and chemical composition but different inner structures provide an effective way to investigate the relationship between inner structure and performance.

Nitrogen, phosphorus co-doped hollow porous carbon microspheres as an oxidase-like electrochemical sensor for baicalin

The extraordinary properties and unique structure of porous carbon has rapidly turned into a new favorite in the development and application of high-performance electrocatalytic sensor. Nitrogen, phosphorus co-doped hollow porous...

Interfacial Electronic Effects in Co@N-Doped Carbon Shells Heterojunction Catalyst for Semi-Hydrogenation of Phenylacetylene

Metal-supported catalyst with high activity and relatively simple preparation method is given priority to industrial production. In this work, this study reported an easily accessible synthesis strategy to prepare Mott-Schottky-type N-doped carbon encapsulated metallic Co (Co@N_p+gC) catalyst by high-temperature pyrolysis method in which carbon nitride (g-C₃N₄) and dopamine were used as support and nitrogen source. The prepared Co@N_p+gC presented a Mott-Schottky effect; that is, a strong electronic interaction of metallic Co and N-doped carbon shell was constructed to lead to the generation of Mott-Schottky contact. The metallic Co, due to high work function as compared to that of N-doped carbon, transferred electrons to the N-doped outer shell, forming a new contact interface. In this interface area, the positive and negative charges were redistributed, and the catalytic hydrogenation mainly occurred in the area of active charges. The Co@N_p+gC catalyst showed excellent catalytic activity in the hydrogenation of phenylacetylene to styrene, and the selectivity of styrene reached 82.4%, much higher than those of reference catalysts. The reason for the promoted semi-hydrogenation of phenylacetylene was attributed to the electron transfer of metallic Co, as it was caused by N doping on carbon.

Hollow nitrogen-doped carbon nanospheres as cathode catalysts to enhance oxygen reduction reaction in microbial fuel cells treating wastewater

Hollow nanospheres play a pivotal role in the electro-catalytic oxygen reduction reaction (ORR), which is a crucial step in microbial fuel cell (MFC) device. Herein, the hollow nitrogen-doped carbon nanospheres (HNCNS) were synthesized with the sacrifice of silica coated carbon nanospheres (CNS@SiO₂) as template. HNCNS remarkably enhanced the ORR activity compared to the solid carbon and solid silica spheres. By tuning calcination temperature (800-1100 °C), the surface chemistry properties of HNCNS were effectively regulated. The optimal HNCNS-1000 catalyst which was calcined at 1000 °C exhibited the highest ORR activity in neutral media with the onset potential of 0.255 V and half-wave potential of -0.006 V (vs. Ag/AgCl). Single chamber MFC (SCMFC) assembled with HNCNS-1000 cathode unveiled comparable activity to a conventional Pt/C reference. It showed the highest maximum power density of 1307 ± 26 mW/m², excellent output stability of 5.8% decline within 680 h, chemical oxygen demand (COD) removal of 94.0 ± 0.3% and coulombic efficiency (CE) of 7.9 ± 0.9%. These excellent results were attributed to a cooperative effect of the optimized surface properties (e.g., structural defects, relative content of pyrrolic nitrogen and specific surface area) and the formation of hollow nanosphere structure. Furthermore, the positive linear relationship of the structural defects and pyrrolic nitrogen species with the maximum power generation in SCMFC were clearly elucidated. This study demonstrated that the cost effective HNCNS-1000 was a promising alternative to commercial Pt/C catalyst for practical application in MFCs treating wastewater. Our result revealed the effectiveness of MFC fabricated with HNCNS-1000 cathode catalyst in terms of power generation and wastewater treatment.

A Mild CO2 Etching Method To Tailor the Pore Structure of Platinum-Free Oxygen Reduction Catalysts in Proton Exchange Membrane Fuel Cells

The structural tailoring of pores is essential to high-performance Fe/N/C electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Current strategies for pore structure engineering are usually accompanied with a drastic change of the intrinsic activity-related surface, which may mask the real effects of the porous structure on ORR activity. Herein, a mild carbon dioxide (CO₂) etching method was used to flexibly tailor the pore structure of Fe/N/C electrocatalysts without drastic changes in their surface structure and property. In this way, via employing the Fe/N/C electrocatalysts as a model, the intrinsic impact of the pore structure on ORR activity was revealed. In addition, the CO₂ etching method developed a high-quality electrocatalyst (sample Fe/N/C-5% CO₂) with polarization performance exceeding that of the commercial Pt/C catalyst in the fuel cell working voltage region (>0.65 V). This work will promote the ongoing intensive studies on the rational design of the pore structures in the Fe/N/C electrocatalysts.

High Capacity and Fast Kinetics of Potassium-Ion Batteries Boosted by Nitrogen-Doped Mesoporous Carbon Spheres

In view of rich potassium resources and their working potential, potassium-ion batteries (PIBs) are deemed as next generation rechargeable batteries. Owing to carbon materials with the preponderance of durability and economic price, they are widely employed in PIBs anode materials. Currently, porosity design and heteroatom doping as efficacious improvement strategies have been applied to the structural design of carbon materials to improve their electrochemical performances. Herein, nitrogen-doped mesoporous carbon spheres (MCS) are synthesized by a facile hard template method. The MCS demonstrate larger interlayer spacing in a short range, high specific surface area, abundant mesoporous structures and active sites, enhancing K-ion migration and diffusion. Furthermore, we screen out the pyrolysis temperature of 900 °C and the pore diameter of 7 nm as optimized conditions for MCS to improve performances. In detail, the optimized MCS-7-900 electrode achieves high rate capacity (107.9 mAh g^-1 at 5000 mA g^-1) and stably brings about 3600 cycles at 1000 mA g^-1. According to electrochemical kinetic analysis, the capacitive-controlled effects play dominant roles in total storage mechanism. Additionally, the full-cell equipped MCS-7-900 as anode is successfully constructed to evaluate the practicality of MCS.

Monodisperse Ultrahigh Nitrogen-Containing Mesoporous Carbon Nanospheres from Melamine-Formaldehyde Resin

An aqueous emulsion polymerization self-assembly approach is demonstrated for the first time to synthesize ultrahigh nitrogen containing mesoporous polymer nanospheres, using melamine-formaldehyde resin oligomers as precursors. In the synthesis, change from alkaline to acidic conditions is critical for the formation of monodisperse mesostructured polymer nanospheres. Owing to unique structure of triazine stabilized in the covalent polymeric networks during the pyrolysis process, the derived mesoporous carbon nanospheres possess an ultrahigh nitrogen content (up to 15.6 wt%) even after pyrolysis at 800 °C, which is the highest nitrogen content among mesoporous carbon nanospheres. Furthermore, these monodisperse mesoporous carbon nanospheres possess a high surface area (≈883 m² g^-1 ) and large pore size (≈8.1 nm). As an anode for sodium-ion batteries, the ultrahigh nitrogen-containing mesoporous carbon nanospheres exhibit superior rate capability (117 mAh g^-1 at a high current density of 3 A g^-1 ) and high reversible capacity (373 mAh g^-1 at 0.06 A g^-1 ), indicating a promising material for energy storage.

Precisely Controlled Vertical Alignment in Mesostructured Carbon Thin Films for Efficient Electrochemical Sensing

Two-dimensional carbon materials, incorporating a large mesoporosity, are attracting considerable research interest in various fields such as catalysis, electrochemistry, and energy-related technologies owing to their integrated functionalities. However, their potential applications, which require favorable mass transport within mesopore channels, are constrained by the undesirable and finite mesostructural configurations due to the immense synthetic difficulties. Herein, we demonstrate an oriented monomicelle assembly strategy, for the facile fabrication of highly ordered mesoporous carbon thin films with vertically aligned and permeable mesopore channels. Such a facile and reproducible approach relies on the swelling and fusion effect of hydrophobic benzene homologues for directional monomicelle assembly. The orientation assembly process shows precise controllability and great universality, affording mesoporous carbon films with a cracking-free structure over a centimeter in size, highly tunable thicknesses (13 to 85 nm, an interval of ∼12 nm), mesopore size (8.4 to 13.5 nm), and switchable growth substrates. Owing to their large permeable mesopore channels, electrochemical sensors based on vertical mesoporous carbon films exhibit an ultralow limit of detection (50 nmol L^-1) and great sensitivity in dopamine detection.

Micropore-Rich Yolk-Shell N-doped Carbon Spheres: An Ideal Electrode Material for High-Energy Capacitive Energy Storage

Increasing the energy density of electrochemical double layer capacitors (EDLCs) can broaden their applications in energy storage but remains a formidable challenge. Herein, micropore-rich yolk-shell structured N-doped carbon spheres (YSNCSs) were constructed by a one-pot surfactant-free self-assembly method in aqueous solution. The resultant YSNCSs after activation possessed an ultrahigh surface area of 2536 m²  g^-1 , among which 80 % was contributed from micropores. When applied in EDLCs, the activated YSNCSs demonstrated an unprecedentedly high capacitance (270 F g^-1 at 1 A g^-1 ) in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF₄ ]) ionic liquid, affording an ultrahigh energy density (133 Wh kg^-1 at 943 W kg^-1 ). The present contribution provides insight into engineering porous carbons for capacitive energy storage.

Molecular Level Design of Nitrogen-Doped Well-Defined Microporous Carbon Spheres for Selective Adsorption and Electrocatalysis

Nitrogen-doped porous carbon spheres have attracted great interest in diversified fields owing to their unique physical and chemical properties. However, the synthesis of nitrogen-doped porous carbon spheres with hierarchical superstructures and refined micropore structures is still a challenge. Herein, we develop a molecular-scale silica templating strategy to prepare nitrogen-doped microporous carbon spheres (MCSSs) with high porosity and a well-defined micropore structure. Octa(aminophenyl) polyhedral oligomeric silsesquioxane is used as a building block in MCSS precursors to provide precise molecular-scale templating and nitrogen doping. The morphology of MCSSs can be easily tuned by choosing the proper solvent. The as-synthesized MCSS with a large surface area (2036 m² g^-1), narrow micropore size distribution, nitrogen doping, and hierarchical geometry can serve as an efficient selective adsorbent for CO₂ and organic pollutants. Furthermore, the MCSS decorated with Fe-N-C active sites (MCSS-Fe) shows enhanced electrocatalytic ORR activity in alkaline solution. This novel approach may open a new avenue for controllable fabrication of porous carbon spheres with desired geometry and well-designed pore structure and show potential applications in selective adsorption and catalysis.

Multi-Yolk-Shell MnO@Carbon Nanopomegranates with Internal Buffer Space as a Lithium Ion Battery Anode

Multi-yolk-shell MnO@mesoporous carbon (MnO@m-carbon) nanopomegranates, featuring MnO nanoparticles within cavities of m-carbon with internal space between the MnO nanoparticle and a cavity carbon shell, were subtly constructed. Moreover, the buffer space was well controlled by means of regulating the size of the cavity in m-carbon or the content of MnO. The results of electrochemical measurements demonstrated that MnO(10)@m-carbon(22) nanopomegranates (MnO nanoparticle, 15 nm; cavity size, 22 nm) had the best cycling and rate performance for lithium ion storage. The pomegranate-like MnO@m-carbon nanostructures have shown several advantages for their excellent performance: the nanocavity in m-carbon can restrict the growth and agglomeration of MnO nanoparticles; the well-interconnected mesoporous carbon matrix provides a "highway" for electrons and lithium ion transport; the voids between the MnO nanoparticle and cavity shell can alleviate the volume expansion.

Controllable synthesis of porous tubular carbon by a Ag+-ligand-assisted Stöber-silica/carbon assembly process

Herein, in this study, we utilized Ag+-ligand interactions for critically regulating the morphology of carbon by the Stöber-silica/carbon co-assembly method for the first time. Tetraethyl orthosilicate (TEOS) and resorcinol/formaldehyde (RF) assemble upon dictation by Ag+ and pyridyl-functionalized surfactants, producing porous carbon tubes (RF1) with a high surface area of 696 m2 g-1 and accessible mesopores ∼15 nm in size. Furthermore, when using tetrapropyl orthosilicate (TPOS) with a slower hydrolysis rate than that of TEOS, carbon tubes (RF2) with enhanced uniformity and a surface area as high as 2112 m2 g-1 are generated. Additionally, when using dopamine hydrochloride instead of RF as a carbon precursor, tubular polydopamine (TDA) with lengths of tens of microns is fabricated, which exhibits excellent catalytic activity toward oxygen reduction reactions in alkaline solutions due to its unique structural feature, a high surface area of 1350 m2 g-1, metallic silver remains of 8.3 wt%, and a rich nitrogen content of 3.6 wt%. This work sheds light on the engineering of a micellar soft template and synthesizing novel nanostructures by the extension of the Stöber method.

Carbon materials for ion-intercalation involved rechargeable battery technologies

The development of carbon electrode materials for rechargeable batteries is reviewed from the perspective of structural features, electrochemistry, and devices.

Tailoring Polymer Colloids Derived Porous Carbon Spheres Based on Specific Chemical Reactions

Porous carbon spheres derived from polymer colloids with regular geometry, monodispersed morphology, well-controlled contents and structures play important roles in many areas of application, such as energy storage/conversion, gas adsorption/separation, catalysis, and chemo-photothermal therapy. Suitable polymerization reaction and synthetic strategy are both critical for the obtainment of stable polymer colloids as carbon precursors. Basic polymerization reactions are the cornerstones of synthetic strategies, which directly provides the direct molecular-based design of functionalized polymer/carbon spheres. Thus, this progress report mainly focuses on the summary of suitable polymerization reactions for colloidal polymer derived porous carbon spheres. Recent advances in the synthetic strategies and applications are also discussed, including their corresponding polymerization reactions. Finally, the perspectives for the development of polymer derived porous carbon spheres are provided based on the controlled synthesis of polymer colloids and optimization over the carbonization process to achieve highly functionalized carbon spheres for practical applications.

Highly active Fe-N-doped porous hollow carbon nanospheres as oxygen reduction electrocatalysts in both acidic and alkaline media

Hierarchical iron-nitrogen-codoped porous hollow carbon spheres have been synthesized by using melamine-formaldehyde (MF) resin spheres as templates, nitrogen sources and pore-forming agents. FeCl3, 1,10-phenanthroline and carbon black were used as iron, nitrogen and carbon sources. The as-obtained porous hollow carbon spheres possess a high specific surface area of 807 m2 g-1, as well as exhibited excellent electrocatalytic activity for the oxygen reduction reaction (ORR) in both acidic and alkaline media. In 0.1 M HClO4 solution, the onset potential was 0.857 V (vs. RHE) and the half-wave potential was 0.715 V, which are only 78 and 80 mV less than those of the 20% Pt/C catalyst, respectively. In addition, in 0.1 M KOH solution, the onset potential was 1.017 V and the half-wave potential was 0.871 V for the ORR, which are 22 and 28 mV more positive than those of the Pt/C catalyst, respectively. Meanwhile, the catalyst also exhibited excellent methanol tolerance and long-term durability with a more effective four-electron pathway compared to the 20% Pt/C catalyst in both acidic and alkaline media. When used as an air-cathode catalyst for a Zn-air battery, the maximum power density of a Zn-air battery with the MF-C-Fe-Phen-800 cathode was 235 mW cm-2 at a high current density of 371 mA cm-2, and a high open-circuit potential of 1.654 V, superior to that of Pt/C (199 mW cm-2, 300 mA cm-2, 1.457 V). A series of designed experiments suggested that the remarkable performance was attributed to the high specific area, hollow carbon spheres, unique hierarchical micro-mesoporous structures, high contents of pyridinic-N and graphitic-N. The superiority of the as-prepared catalyst makes it promising for use in practical applications.

Light-enhanced sponge-like carbon nanozyme used for synergetic antibacterial therapy

Bacterial infection and the issue of antibiotic resistance have become one of the major public health problems worldwide. Thus, searching for new antibacterial agents is urgently required. Hydrogen peroxide, H2O2, as a traditional bactericide, is applied widely for medical treatments. However, the relatively high concentration of H2O2 used in a clinical setting usually inhibits wound healing and even damages normal tissues during disinfection. Here, we synthesized N-doped sponge-like carbon spheres (N-SCSs), which showed excellent mimicking activities for multiple enzymes, including peroxidase, oxidase, superoxide dismutase, and catalase. We then utilized the peroxidase-like activity of the N-SCSs to convert low-concentration H2O2 into radical oxygen species to resist bacteria. The data showed that the antibacterial performance of H2O2 against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and multidrug-resistant bacteria was improved through the peroxidase-like catalytic reaction of N-SCSs. Importantly, besides generating heat against bacteria, near-infrared laser exposure also promoted the peroxidase activity of N-SCSs, to further generate radical oxygen species to kill bacteria. In addition, this catalytic-photothermal antibacterial strategy demonstrated accelerated recovery of infected wounds in an animal model. Thus, our work provides a new synergetic anti-infection strategy, and further expands the application of carbon-based nanozymes in biomedicine.

Nitrogen-doped Carbon Nanospheres-Modified Graphitic Carbon Nitride with Outstanding Photocatalytic Activity

Metals and metal oxides are widely used as photo/electro-catalysts for environmental remediation. However, there are many issues related to these metal-based catalysts for practical applications, such as high cost and detrimental environmental impact due to metal leaching. Carbon-based catalysts have the potential to overcome these limitations. In this study, monodisperse nitrogen-doped carbon nanospheres (NCs) were synthesized and loaded onto graphitic carbon nitride (g-C₃N₄, GCN) via a facile hydrothermal method for photocatalytic removal of sulfachloropyridazine (SCP). The prepared metal-free GCN-NC exhibited remarkably enhanced efficiency in SCP degradation. The nitrogen content in NC critically influences the physicochemical properties and performances of the resultant hybrids. The optimum nitrogen doping concentration was identified at 6.0 wt%. The SCP removal rates can be improved by a factor of 4.7 and 3.2, under UV and visible lights, by the GCN-NC composite due to the enhanced charge mobility and visible light harvesting. The mechanism of the improved photocatalytic performance and band structure alternation were further investigated by density functional theory (DFT) calculations. The DFT results confirm the high capability of the GCN-NC hybrids to activate the electron-hole pairs by reducing the band gap energy and efficiently separating electron/hole pairs. Superoxide and hydroxyl radicals are subsequently produced, leading to the efficient SCP removal.

N-Doped carbon nanospheres with nanocavities to encapsulate manganese oxides as ORR electrocatalysts

MnO₂(Mn₃O₄or MnO) nanoparticles embedded in nanocavities of N-doped carbon nanospheres as ORR electrocatalysts have been reported.

Synthesis of mesoporous carbon with tunable pore size for supercapacitors

Mesoporous carbon (MC) has wide applications, including in drug delivery, catalysis, absorption, energy storage/conversion, etc.

N,S-Codoped hierarchical porous carbon spheres embedded with cobalt nanoparticles as efficient bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

Rational design and fabrication of cost-effective, efficient bifunctional electrocatalysts is fundamentally important for the air cathode of metal-air batteries. Herein, a Co(ii) ion-driven self-assembly strategy is described for the synthesis of cobalt-based nanostructured transition metal compounds (Co-NTMCs) embedded in nitrogen and sulfur codoped hierarchical porous carbon submicrospheres (Co-NTMCs@NSC), where condensation of thiourea-ethylenediamine-formaldehyde resin (TEFR) is induced by Co(ii) ions which is simultaneously assembled with polydopamine to form a multifunctional precursor through coordinated interaction. The resulting Co-NTMCs@NSC sample comprises abundant hierarchical porous textures, a high content of active cobalt species including the nanoparticles of Co, Co₃O₄ and amorphous CoS_x, and a considerable amount of defective structures. These characteristics lead to remarkable oxygen electrocatalytic activities, with a half-wave potential of +0.833 V vs. RHE, which is comparable to that of commercial Pt/C for the oxygen reduction reaction (ORR), and a lower overpotential of 284 mV than RuO₂ at 10 mA·cm^-2 for the oxygen evolution reaction (OER) in alkaline media. Furthermore, its operational stability is also much higher than that of commercial RuO₂ and Pt/C catalysts. When used as a breathing air electrode for Zn-air batteries, Co-NTMCs@NSC shows a higher open-circuit voltage (1.509 V), higher discharge power density (262 mW cm^-2) and better charge-discharge reversibility than commercial Pt/C. The results from the present work suggest that controlled assembly of functional polymers may be exploited for the preparation of doped carbon/metal nanoparticle nanocomposites as viable, high-performance catalysts for electrochemical energy technologies.

One-Step Synthesis of Monodispersed Mesoporous Carbon Nanospheres for High-Performance Flexible Quasi-Solid-State Micro-Supercapacitors

Cost-effective synthesis of carbon nanospheres with a desirable mesoporous network for diversified energy storage applications remains a challenge. Herein, a direct templating strategy is developed to fabricate monodispersed N-doped mesoporous carbon nanospheres (NMCSs) with an average particle size of 100 nm, a pore diameter of 4 nm, and a specific area of 1093 m² g^-1 . Hexadecyl trimethyl ammonium bromide and tetraethyl orthosilicate not only play key roles in the evolution of mesopores but also guide the assembly of phenolic resins to generate carbon nanospheres. Benefiting from the high surface area and optimum mesopore structure, NMCSs deliver a large specific capacitance up to 433 F g^-1 in 1 m H₂ SO₄ . The NMCS electrodes-based symmetric sandwich supercapacitor has an output voltage of 1.4 V in polyvinyl alcohol/H₂ SO₄ gel electrolyte and delivers an energy density of 10.9 Wh kg^-1 at a power density of 14014.5 W kg^-1 . Notably, NMCSs can be directly applied through the mask-assisted casting technique by a doctor blade to fabricate micro-supercapacitors. The micro-supercapacitors exhibit excellent mechanical flexibility, long-term stability, and reliable power output.

Controllable synthesis of mesoporous carbon microspheres with renewable water glass as a template for lithium-sulfur batteries

Mesoporous carbon microspheres (MCMs) were prepared via a spray drying-assisted template method using resorcinol-formaldehyde as the carbon precursor and water glass as the template. The pore structure could be controlled by adjusting the hydrolysis time, hydrolysis temperature, concentration of the water glass and reactant ratio. Water glass could be recycled after use, making this strategy environmentally friendly and cost-effective. MCMs with three-dimensional interconnected networks, high surface area (852-1549 m² g^-1), large pore volume (1.7-2.1 cm³ g^-1) and controllable pore diameter (3.8-15.1 nm) were constructed and have good electrical conductivity and a large volume for sulfur loading. The S/MCM composites with abundant residual nanochannels could not only benefit for the diffusion of electrolyte but also improve the utilization of sulfur and buffer the volume expansion of sulfur. The MCMs with relatively small mesopores manifest a high reversible capacity and rate performance owing to the strong confinement effect of polysulfides. MCM-1 delivered an initial capacity of 888.7 mA h g^-1 under 0.5C with a capacity retention of 700.5 mA h g^-1 after 100 cycles. The good electrochemical performance confirms that mesoporous carbon microspheres can be an excellent host material for sulfur cathodes.

A Crystalline, 2D Polyarylimide Cathode for Ultrastable and Ultrafast Li Storage

Organic electrode materials are of long-standing interest for next-generation sustainable lithium-ion batteries (LIBs). As a promising cathode candidate, imide compounds have attracted extensive attention due to their low cost, high theoretical capacity, high working voltage, and fast redox reaction. However, the redox active site utilization of imide electrodes remains challenging for them to fulfill their potential applications. Herein, the synthesis of a highly stable, crystalline 2D polyarylimide (2D-PAI) integrated with carbon nanotube (CNT) is demonstrated for the use as cathode material in LIBs. The synthesized polyarylimide hybrid (2D-PAI@CNT) is featured with abundant π-conjugated redox-active naphthalene diimide units, a robust cyclic imide linkage, high surface area, and well-defined accessible pores, which render the efficient utilization of redox active sites (82.9%), excellent structural stability, and fast ion diffusion. As a consequence, high rate capability and ultrastable cycle stability (100% capacity retention after 8000 cycles) are achieved in the 2D-PAI@CNT cathode, which far exceeds the state-of-the-art polyimide electrodes. This work may inspire the development of novel organic electrodes for sustainable and durable rechargeable batteries.

Versatile Nanoemulsion Assembly Approach to Synthesize Functional Mesoporous Carbon Nanospheres with Tunable Pore Sizes and Architectures

Functional mesoporous carbons have attracted significant scientific and technological interest owning to their fascinating and excellent properties. However, controlled synthesis of functional mesoporous carbons with large tunable pore sizes, small particle size, well-designed functionalities, and uniform morphology is still a great challenge. Herein, we report a versatile nanoemulsion assembly approach to prepare N-doped mesoporous carbon nanospheres with high uniformity and large tunable pore sizes (5-37 nm). We show that the organic molecules (e.g., 1,3,5-trimethylbenzene, TMB) not only play an important role in the evolution of pore sizes but also significantly affect the interfacial interaction between soft templates and carbon precursors. As a result, a well-defined Pluronic F127/TMB/dopamine nanoemulsion can be facilely obtained in the ethanol/water system, which directs the polymerization of dopamine into highly uniform polymer nanospheres and their derived N-doped carbon nanospheres with diversely novel structures such as smooth, golf ball, multichambered, and dendritic nanospheres. The resultant uniform dendritic mesoporous carbon nanospheres show an ultralarge pore size (∼37 nm), small particle size (∼128 nm), high surface area (∼635 m² g^-1), and abundant N content (∼6.8 wt %), which deliver high current density and excellent durability toward oxygen reduction reaction in alkaline solution.