Confined Self-Assembly in Two-Dimensional Interlayer Space: Monolayered Mesoporous Carbon Nanosheets with In-Plane Orderly Arranged Mesopores and a Highly Graphitized Framework

A facile synthesis of an Fe/N-doped ultrathin carbon sheet for highly efficient oxygen reduction reaction

Fe/N-Doped ultrathin carbon sheet was synthesized. Fe₃C/NC-800 exhibited an outstanding behavior toward ORR catalysis with a catalyst loading of 150 μg cm⁻², which surpassed most of the non-precious metal electrocatalysts reported.

The adsorption behavior and mechanism of Cr(VI) on facile synthesized mesoporous NH-SiO2

An efficient Cr(VI) adsorbent, mesoporous amine-functionalized silica (NH-SiO₂), was successfully synthesized within 2 h by a facile one-step route under room temperature and aqueous solution. The structure properties of the obtained materials were characterized by N₂ adsorption-desorption isotherm, XRD, TEM, and FT-IR. The Cr(VI) removal performance was investigated by batch experiment. It was found that Cr(VI) removal performance was dependent on solution pH, and the removal efficiency is above 90% for initial pH in the range of 1.0-4.0. The adsorption process was obeyed by pseudo-second-order model, and the equilibrium adsorption data were fitted well by Langmuir model. The maximum monolayer adsorption capacity was 205.76 mg/g at pH 2.0, which was larger than that of traditional two-step tri-amine-functionalized MCM-41. Additionally, high selectivity was exhibited in NH-SiO₂ for removal Cr(VI) from co-presence anions Cl^-, NO₃^-, PO₄^3-, SO₄^2-, and SiO₃^2-. Furthermore, the spent NH-SiO₂ could be regenerated by 0.005 M NaOH, and Cr(VI) removal is above 92% after NH-SiO₂ recycled four. From the analyzed results of adsorption energy, FT-IR, and XPS, the electrostatic attraction between protonated amine group and HCrO₄^- was the mainly adsorption mechanism. And then some adsorbed Cr(VI) was reduced to low toxicity Cr(III) on the adsorbent surface by electron transfer from nitrogen in -NBr group to Cr(VI).

Silicon nanoparticles coated with nanoporous carbon as a promising anode material for lithium ion batteries

As a promising anode candidate, silicon (Si) nanoparticles have been widely studied for use in lithium ion batteries.

Precise control of density and strength of acid sites of MFI-type zeolite nanoparticles via simultaneous isomorphous substitution by Al and Fe

The co-incorporation of Al and Fe at various relative ratios into the MFI-type zeolite framework enabled linear control of the density and strength of acid sites, and such well-tuned acidity led to a better catalyst lifetime.

Boron-doped carbon nanodots dispersed on graphitic carbon as high-performance catalysts for acetylene hydrochlorination

Boron-doped carbon nanodot materials, comprising evenly distributed BC₃-nanodots in a layered carbon matrix, are prepared through a pre-assembly assisted carbonization synthetic strategy.

Fabrication of a Novel Antifouling Polysulfone Membrane with in Situ Embedment of Mxene Nanosheets

Membrane fouling is still a critical issue for the application of ultrafiltration, which has been widely used in water treatment due to its efficiency and simplicity. In order to improve the antifouling property, a new 2D material MXene was used to fabricate composite ultrafiltration membrane with the approach of in situ embedment during the phase inversion process in this study. Scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), water contact angle, bovine serum albumin rejection and porosity measurements were utilized to characterize the prepared membranes. Due to the hydrophilicity of the MXene, the composite membranes obtained higher hydrophilicity, confirmed by the decreased water contact angle. All the modified membranes had a high bovine serum albumin rejection above 90% while that of the pristine polysulfone membrane was 77.48%. The flux recovery ratio and the reversible fouling ratio of the membranes were also improved along with the increasing content of the MXene. Furthermore, the highest flux recovery ratio could also reach 76.1%. These indicated the good antifouling properties of MXene composite membranes. The enhanced water permeability and protein rejection and excellent antifouling properties make MXene a promising material for antifouling membrane modification.

A highly alkaline-stable metal oxide@metal–organic framework composite for high-performance electrochemical energy storage

Most metal–organic frameworks (MOFs) hardly maintain their physical and chemical properties after exposure to alkaline aqueous solutions, thus precluding their use as potential electrode materials for electrochemical energy storage devices. Here, we present the design and synthesis of a highly alkaline-stable metal oxide@MOF composite, Co3O4 nanocube@Co-MOF (Co3O4@Co-MOF), via a controllable and facile one-pot hydrothermal method under highly alkaline conditions. The obtained composite possesses exceptional alkaline stability, retaining its original structure in 3.0 M KOH for at least 15 days. Benefitting from the exceptional alkaline stability, unique structure, and larger surface area, the Co3O4@Co-MOF composite shows a specific capacitance as high as 1020 F g−1 at 0.5 A  g−1 and a high cycling stability with only 3.3% decay after 5000 cycles at 5 A g−1. The as-constructed solid-state flexible device exhibits a maximum energy density of 21.6 mWh cm−3.

Pyrolysis of Chinese chestnut shells: Effects of temperature and Fe presence on product composition

To understand the role of Fe on biomass pyrolysis, Fe-catalyzed biomass pyrolysis in a fixed-bed reactor was investigated. It was found that the introduction of Fe increased the yields of gases and solid char while decreasing the yield of liquid oil. With increasing temperature, Hydrogen content in gaseous products obtained in the presence of Fe increased, while that of CH₄ decreased. In the case of liquid oil, the introduction of Fe promoted the formation of ketones and acids at 400-600 °C, and these species became dominant (67.51%) at 700-800 °C. Finally, solid char obtained in the presence of Fe at 700-800 °C featured a larger pore volume, specific surface area, and graphitization degree, and was characterized by a mesoporous structure with narrow pores size distribution (∼5.3 nm).

Facile synthesis of hierarchical mesopore-rich activated carbon with excellent capacitive performance

Mesoporous carbons attract increasing attention owing to their potential applications in supercapacitors. So far, controlled synthesis of mesoporous carbons with a narrow pore size distribution relies largely on the complicated template methods. To avoid the use of templates, a surfactant-free emulsion polymerization method is presented for the fabrication of a melamine-modified phenolic resin microrod (MPRR) assembled by micron-sized spherical cells and thin walls. In addition, one-step KOH activation strategy is adopted to synthesize hierarchical mesoporous activated carbon with 2-10 nm narrow mesopores by using MPRR as carbon precursors. The as-prepared mesoporous activated carbon has a high specific surface area of about 2758 m² g^-1 and a mesopore volume of 0.54 cm³ g^-1 (calculated by density functional theory), comprising ∼43.5% of total pore volume (∼1.43 cm³ g^-1). Hierarchical mesopores can significantly accelerate ion transfer and increase micropore accessibility, which endow the carbon with high specific capacitance equal to 409 F g^-1 at 0.1 A g^-1 and 268 F g^-1 at 100 A g^-1 in 6 M KOH electrolyte, with a high capacitance retention of 66%. Moreover, the assembled symmetric supercapacitor also exhibits good cycling stability in KOH electrolyte and delivers high power density equal to 12080 W kg^-1 when energy density is 5.02 Wh kg^-1. This finding provides an insight into directional tailoring of mesoporous structures of phenolic resin-based carbon materials at the molecular level for high-performance supercapacitors.

Membrane-Free Hybrid Capacitive Deionization System Based on Redox Reaction for High-Efficiency NaCl Removal

Capacitive deionization (CDI) is a promising technology for desalination due to its advantages of low driven energy and environmental friendliness. However, the ion removal capacity (IRC) of CDI is insufficient for practical application because such a capacity is limited by the available surface area of the carbon electrode for ion absorption. Thus, the development of a novel desalination technology with high IRC and low cost is vital. Here, a membrane-free hybrid capacitive deionization system (HCDI) with hollow carbon@MnO₂ (HC@MnO₂) to capture sodium via redox reaction and hollow carbon sphere with net positive surface charges (PHC) for chloride adsorption is introduced. The as-obtained HC@MnO₂ with unique structure and high conductivity can improve the utilization of MnO₂ pseudocapacitive electrodes. Meanwhile, the PHC can selectively adsorb Cl^- and prevent the adsorption of Na⁺ due to electrostatic repulsion. As expected, the membrane-free HCDI system demonstrates excellent desalination performance. The system's IRC and maximum removal rate are 30.7 mg g^-1 and 7.8 mg g^-1 min^-1, respectively. Moreover, the proposed system has a low cost because of the absence of expensive ion exchange membranes (IEM), which is suitable for practical application. The excellent performance of this HCDI makes it a promising desalination technology for future use.

Robust Negative Electrode Materials Derived from Carbon Dots and Porous Hydrogels for High-Performance Hybrid Supercapacitors

Hybrid supercapacitors generally show high power and long life spans but inferior energy densities, which are mainly caused by carbon negative electrodes with low specific capacitances. To improve the energy densities, the traditional methods include optimizing pore structures and modifying pseudocapacitive groups on the carbon materials. Here, another promising way is suggested, which has no adverse effects to the carbon materials, that is, constructing electron-rich regions on the electrode surfaces for absorbing cations as much as possible. For this aim, a series of hierarchical porous carbon materials are produced by calcinating carbon dots-hydrogel composites, which have controllable surface states including electron-rich regions. The optimal sample is employed as the negative electrode to fabricate hybrid supercapacitors, which show remarkable specific energy densities (up to 62.8-90.1 Wh kg^-1 ) in different systems.

Investigation of the mechanism of chromium removal in (3-aminopropyl)trimethoxysilane functionalized mesoporous silica

We are proposed that a possible mechanism for Cr(VI) removal by functionalized mesoporous silica. Mesoporous silica was functionalized with (3-aminopropyl)trimethoxysilane (APTMS) using the post-synthesis grafting method. The synthesized materials were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption-desorption analysis, Fourier-transform infrared (FT-IR), thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS) to confirm the pore structure and functionalization of amine groups, and were subsequently used as adsorbents for the removal of Cr(VI) from aqueous solution. As the concentration of APTMS increases from 0.01 M to 0.25 M, the surface area of mesoporous silica decreases from 857.9 m²/g to 402.6 m²/g. In contrast, Cr(VI) uptake increases from 36.95 mg/g to 83.50 mg/g. This indicates that the enhanced Cr(VI) removal was primarily due to the activity of functional groups. It is thought that the optimum concentration of APTMS for functionalization is approximately 0.05 M. According to XPS data, NH₃⁺ and protonated NH₂ from APTMS adsorbed anionic Cr(VI) by electrostatic interaction and changed the solution pH. Equilibrium data are well fitted by Temkin and Sips isotherms. This research shows promising results for the application of amino functionalized mesoporous silica as an adsorbent to removal Cr(VI) from aqueous solution.

Materials Nanoarchitectonics Using 2D Layered Materials: Recent Developments in the Intercalation Process

Layered inorganic solids as an attractive classification of 2D materials offer material diversity and a wide range of interesting properties. Layered inorganic solids provide an expandable 2D nanospace between each individual layer, the so called interlayer space, to accommodate/arrange guest species such as molecules, nanoparticles, and polymer chains and design unique nanoarchitectures, resulting in the production of intercalation compounds showing different properties in comparison to those of virgin layered materials and guest species. Layered inorganic solids can also be exfoliated to result in nanosheet production. Further ordering of exfoliated nanosheets is also possible via different methods and normally leads to creating soft materials presenting properties and applications different from that of relatively rigid intercalation compounds. Here, the latest studies and up-to-date developments on the possible techniques of designing novel types of materials using layered inorganic solids are specifically highlighted.

Recent Progress on Two-Dimensional Nanoflake Ensembles for Energy Storage Applications

The rational design and synthesis of two-dimensional (2D) nanoflake ensemble-based materials have garnered great attention owing to the properties of the components of these materials, such as high mechanical flexibility, high specific surface area, numerous active sites, chemical stability, and superior electrical and thermal conductivity. These properties render the 2D ensembles great choices as alternative electrode materials for electrochemical energy storage systems. More recently, recognition of the numerous advantages of these 2D ensemble structures has led to the realization that the performance of certain devices could be significantly enhanced by utilizing three-dimensional (3D) architectures that can furnish an increased number of active sites. The present review summarizes the recent progress in 2D ensemble-based materials for energy storage applications, including supercapacitors, lithium-ion batteries, and sodium-ion batteries. Further, perspectives relating to the challenges and opportunities in this promising research area are discussed.