MOF-derived ZnCo2O4 porous micro-rice with enhanced electro-catalytic activity for the oxygen evolution reaction and glucose oxidation

A porous ZnCo₂O₄ micro-rice like microstructure was synthesized via calcination of a Zn–Co MOF precursor at an appropriate temperature. The as-prepared ZnCo₂O₄ sample presented good electrocatalytic oxygen evolution reaction performance with a small overpotential (η₁₀ = 389 mV) and high stability in basic electrolyte. Furthermore, in basic medium, the as-synthesized ZnCo₂O₄ micro-rice also showed good electrocatalytic activity for glucose oxidation. A ZnCo₂O₄ micro-rice modified glass carbon electrode may be used as a potential non-enzymatic glucose sensor. The excellent electrocatalytic OER and glucose oxidation performances of ZnCo₂O₄ might be attributed to the unique porous structure formed by the nanoparticles. The porous architecture of the micro-rice can provide a large number of electrocatalytically active sites and high electrochemical surface area (ECSA). The result may offer a new way to prepare low-cost and high performance oxygen evolution reaction and glucose oxidation electrocatalysts.

A porous ZnCo₂O₄ micro-rice like microstructure was synthesized via calcination of a Zn–Co MOF precursor at an appropriate temperature.     

Synthesis of a fine LiNi0.88Co0.09Al0.03O2 cathode material for lithium-ion batteries via a solvothermal route and its improved high-temperature cyclic performance

Nickel–Cobalt–Aluminum (NCA) cathode materials for lithium-ion batteries (LIBs) are conventionally synthesized by chemical co-precipitation. However, the co-precipitation of Ni²⁺, Co²⁺, and Al³⁺ is difficult to control because the three ions have different solubility product constants. This study proposes a new synthetic route of NCA, which allows fabrication of fine and well-constructed NCA cathode materials by a high temperature solid-state reaction assisted by a fast solvothermal process. The capacity of the LiNi_0.88Co_0.09Al_0.03O₂ as-synthesized by the solvothermal method was 154.6 mA h g⁻¹ at 55 °C after 100 cycles, corresponding to 75.93% retention. In comparison, NCA prepared by the co-precipitation method delivered only 130.3 mA h g⁻¹ after 100 cycles, with a retention of 63.31%. Therefore, the fast solvothermal process-assisted high temperature solid-state method is a promising candidate for synthesizing high-performance NCA cathode materials.

Nickel–Cobalt–Aluminum (NCA) cathode materials for lithium-ion batteries (LIBs) are conventionally synthesized by chemical co-precipitation.     

Preparation of environmentally friendly acrylic pressure-sensitive adhesives by bulk photopolymerization and their performance

Polyacrylic pressure-sensitive adhesives (PSAs) based on butyl acrylate (BA), 2-hydroxyethyl acrylate (HEA), and acrylic acid (AA) were prepared by a bulk polymerization process triggered by a radical photoinitiator under UV irradiation and UV-crosslinking. 1,6-Hexanediol diacrylate (HDDA) with difunctional groups was introduced into the PSAs to modify semi-interpenetrating network structures. The effect of HDDA content on the pressure-sensitive performance was comprehensively tested. The viscosity of the prepolymer was measured by a rotational viscometer. Prepolymers obtained by a photoinduced process and UV crosslinking process were confirmed via Fourier transform infrared spectroscopy (FTIR). All double bonds participated in the copolymerization without any remaining monomers, which reflected the concept of green environmental protection. Gel content in the crosslinked portion was examined by Soxhlet extraction, whilst the soluble molecular weight of PSAs was characterized by gel permeation chromatography (GPC). The viscoelastic properties of polymer films were determined by dynamic mechanical analysis (DMA). The T_g value and storage modulus (G′) of the PSAs were enhanced with the addition of HDDA. Moreover, three fundamental adhesive properties, i.e. loop tack force, peel force and shear strength of PSAs, were measured. The results showed that UV crosslinking technology achieved a good balance of the three forces with excellent pressure-sensitive properties.

Polyacrylic pressure-sensitive adhesives based on butyl acrylate, 2-hydroxyethyl acrylate, and acrylic acid were prepared by a bulk polymerization process triggered by a radical photoinitiator under UV irradiation and UV-crosslinking.     

Intrinsic defect engineered Janus MoSSe sheet as a promising photocatalyst for water splitting

The Janus MoSSe sheet has aroused significant attention due to its band edge position and intrinsic dipole moment, making it a strong candidate for water splitting photocatalysis. However, weak water adsorption seriously prevents its further application. Here, first-principles calculations are used to explore the effect of intrinsic defects on water adsorption and conversion at the Janus MoSSe sheet. First-principles calculation results clearly show that intrinsic defects (S_vac, Mo_anti, and Mo_int) can effectively alter the interaction between water and the MoSSe sheet. Except for S_vac defects, the adsorption energy of water at Mo_anti or Mo_int defects can be significantly increased by −1.0 to −1.5 eV with respect to the weak water adsorption on a pristine MoSSe sheet of about −0.24 eV. More importantly, the energy barrier for water conversion can be dramatically lowered by 48% to 0.7 eV at Mo_anti or Mo_int defects, together with a more stable final state. Such significant enhancement of the adsorption energy is attributed to the red shift of water energy levels, resulting from the strong interaction between O2p orbitals and Mo3d orbitals. It is shown that the intrinsic defects have the potential to change the photocatalytic reactivity of the surface, and thus this may serve as an important way to design photocatalysts for water splitting.

The Janus MoSSe sheet has aroused significant attention due to its band edge position and intrinsic dipole moment, making it a strong candidate for water splitting photocatalysis.     

The characterization and evaluation of the synthesis of large-ring cyclodextrins (CD9–CD22) and α-tocopherol with enhanced thermal stability

Large-ring cyclodextrins LR-CDs (CD₉–CD₂₂) were obtained from rice starch using cyclodextrin glycosyltransferase (CGTase), and were used as a wall material for embedding α-tocopherol. Complexes of α-tocopherol and LR-CDs were prepared by co-precipitation. A molar ratio of α-tocopherol/LR-CD of 1 : 2 showed the highest encapsulation efficiency. The surface morphology of the complex particles was observed to vary from irregular flakes to the formation of smaller clusters of particles using scanning electron microscopy (SEM). Based on ¹H NMR and FT-IR observations, the inclusion complexes exhibited significant chemical shifts of 0.3 ppm and decreased peak signals. In addition, thermal analysis showed that the microcapsules improved the thermostability of the α-tocopherols. Antioxidant activity analysis proved the stability of α-tocopherol during storage. This study could serve as a reference for the more effective use of LR-CDs as wall materials.

Large-ring cyclodextrins LR-CDs (CD₉–CD₂₂) were obtained from rice starch using cyclodextrin glycosyltransferase (CGTase), and were used as a wall material for embedding α-tocopherol.     

Heavy metal adsorption using structurally preorganized adsorbent

Heavy metal pollution is an essential environmental issue in the world. The current methods present limitations for the removal of low concentration divalent heavy metals from wastewater, such as high cost, unsatisfactory adsorption capacity, and poor reusability. Herein, we designed and prepared a novel chelating adsorbent. The adsorbent was prepared using chloromethyl polystyrene microsphere as a framework material modified by ethylenediaminetetraacetic acid (EDTA) with two types of functional groups and six binding sites in one coordination unit. Each coordination unit of the adsorbent prepared provides two negative charges of two carboxyl groups to balance the two positive charges of the divalent heavy metal ion, and forms coordination bonds through its two nitrogen atoms and two amidic carbonyl groups. This synergistic adsorption effect produced by electrostatic interaction and chelation significantly improves the adsorption capacity. The adsorption of some environmental heavy metals was tested, and high adsorption capacity for Pb(ii) was obtained. The saturated adsorption capacity for Pb(ii) was as high as 352.1 mg g⁻¹, and the effluent concentration of the column experiment was less than 0.20 ppm. Simultaneously, the presence of the amide group shows good anti-interference to alkali metals and alkali soil metals. The result is of considerable significance to the actual wastewater treatment.

The adsorbent had two types of functional groups and six binding sites in one coordination unit. The presence of the amide group shows good anti-interference to alkali metals and alkali soil metals.     

A thermal energy storage composite by incorporating microencapsulated phase change material into wood

Phase change energy storage wood (PCESW) was prepared by using microencapsulated phase change materials (MicroPCM) as thermal energy storage (TES) materials and wood as the matrix. The incorporation of MicroPCM and wood was realized using a vacuum impregnation method. The morphology and microstructure of MicroPCM, delignified wood (DLW) and PCESW were observed by scanning electron microscopy (SEM); the thermal properties including phase change temperature, enthalpy, thermal stability, thermal conductivity of MicroPCM and PCESW were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and laser flash analysis (LFA). The results showed that: (1) delignification improved the porosity of wood and enhanced the impregnation effect, MicroPCM got into the delignified wood successfully and mainly distributed in the vessels; (2) PCESW had excellent energy storage capacity and suitable phase transition temperature for regulating indoor temperature; (3) PCESW had prior thermal stability at room temperature and great durability after 100 heating–cooling cycles; (4) addition of graphene greatly improved the thermal conductivity of PCESW. The TES composite can be used as an indoor temperature regulating material for building energy conservation.

Phase change energy storage wood (PCESW) was prepared by using microencapsulated phase change materials (MicroPCM) as thermal energy storage (TES) materials and wood as the matrix.     

Catalytic activity of porous carbon nitride regulated by polyoxometalates under visible light

A series of porous carbon nitrides modified by different polyoxometalates (POMs) were prepared by the ultrasonic method. POMs were assembled on the surface of mpg-C₃N₄via electrostatic attraction. The catalyst has visible light degradation activity for phenol (λ > 420 nm). mpg-C₃N₄ modified by H₄SiW₁₂O₄₀ with a mass ratio of 1 : 5 showed the highest catalytic activity, which was 3.5 times higher than that of mpg-C₃N₄. As an electron acceptor, polyoxometalate can capture the photoelectron of C₃N₄, which can promote the separation of photocharge and improve the photocatalytic activity. ESR also confirmed that the superoxide radicals play a major role in degradation. The results show that the charge separation efficiency and catalytic activity can be enhanced by polyacids.

A porous composite catalyst is prepared by modifying mpg-C₃N₄ with polyacids through ultrasound. When the mass ratio of SiW₁₂ to mpg-C₃N₄ was 1 : 5, the degradation of phenol showed the best catalytic activity, which was 3.5 times that of mpg-C₃N₄.     

A new oxygen-rich energetic salt dihydrazine tetranitroethide: a promising explosive alternative with high density and good performance

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction. Compound 5 exhibits high crystal density (1.81 g cm⁻³) and impressive detonation velocity (9508 m s⁻¹) and detonation pressure (37.9 GPa), showing potential applications as a high performance explosive and a promising additive of propellants.

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction.

For applications in propellants, explosives and pyrotechnics, new energetic materials are required with high energy, insensitivity, high thermal stability and environment-friendly decomposition gases.¹ To achieve these goals, chemists have adopted a variety of strategies, such as construction of nitrogen-rich compounds,² energetic salts,³ metal organic framework (MOFs)⁴ and cage structure molecules.⁵ Oxygen balance (OB) is an important parameter to weigh the detonation performance of the nitrogen-rich compounds. Generally explosives may exhibit good performance when the OB close to zero.⁶ One conventional method of increasing the OB of energy materials is to introduce nitro groups, a typical high-energy and oxygen-rich substituent.⁷ Recently, gem-nitro and poly-nitro fragments, such as dinitromethyl,⁸ trinitroethyl⁹ and trinitromethyl,¹⁰ have been of interest to researchers. The compounds consisting of poly-nitro groups exhibit good OB, which largely improves their detonation velocities and pressures.¹¹ In our recent study,¹² we considered using tetranitroethylene instead of nitro as a pre-packaged module, linked to insensitive backbones, just like building blocks. The tetranitroethylene fragment has a high nitrogen content, a positive OB, and high energy within the molecule.¹³ The molecules consisting of the tetranitroethylene fragment are expected to be excellent energetic materials with superior properties.¹² But tetranitroethylene is an unstable intermediate, which is difficult to isolate.¹⁴ Hexnitroethane,¹⁵ a stable tetranitroethylene derivative, can be effectively used to synthetize poly-nitro bridged compound (Scheme 1). Previously, we discussed the possibility of constructing poly-nitro bridged-ring compounds with nitrogen-containing heterocycles and tetranitroethylene by using the Diels–Alder reaction.^12,16Open in a separate windowScheme 1Synthetic pathway for poly-nitro bridged compound.¹⁴Dipotassium tetranitroethide,¹⁷ another tetranitroethylene derivative, lead another thought to synthesize high energy salts with the tetranitroethane anion. The salt-based energetic materials often exhibit lower vapour pressure and higher densities than the non-ionic energetic materials.^3c In addition, the energetic salt can improve the properties by selecting different constituent ions.¹⁸ Based on the advantages of high-energy salt, we chose tetranitroethane anion and hydrazine cation to construct energetic salt by considering both energy and sensitivity. The synthetic route can be seen in Scheme 2. The good OB and large amounts of hydrogen-bonds prompt the target compound (dihydrazine tetranitroethide, 5) with suitable sensitivity and good performance. 5 possesses a crystal density of 1.81 g cm⁻³, detonation velocity of 9508 m s⁻¹ and detonation pressure of 37.9 GPa, which are higher than those of RDX. In addition, the salt-formation improves the carcinogenic and high toxic properties of hydrazine.Open in a separate windowScheme 2The route to synthesis of 5.The intermediate dipotassium tetranitroethide (3) was prepared from tetraiodoethylene (1) after two nitrification reactions, according to literature.¹⁹ The suspension of 3 in dichloromethane dissolves in concentrated sulfuric acid to give the solution of tetranitroethane (4) in dichloromethane. Treatment of the solution of 4 with hydrazine hydrate resulted in dihydrazine tetranitroethide (5), a yellow solid precipitated, that was confirmed by single crystal X-ray diffraction. Single crystal 5 is crystallized by using the method of the evaporation of water.Tetranitroethane 4 is also an unstable compound that is soluble in dichloromethane and difficult to isolate. It decomposed and released a brown gas as the solvent removed. Thus, we analysed the UV spectrum of the solution of 4, instead of the pure compound 4. Compared with the experimental and calculated UV spectrum of solution 4 (Fig. 1), we find that the maximum absorption wavelengths of the two curves match well, 240 nm (tested) and 239.5 nm (calculated). It can be inferred that compound 4 would be tetranitroethane.Open in a separate windowFig. 1The UV spectrum curve of tetranitroethane 4.Dihydrazine tetranitroethide 5 in the monoclinic space group C2/c with a good density of 1.81 g cm⁻³ (298 K). The gem-dinitro group is nearly planar, with the torsion angle of O5–N3–C2–N4, 179.52(17)°. However, the torsion angle of N3–C2–C2′–N4′ and N4–C2–C2′–N3′ are 77.57 (255)° and 77.57 (255)°, respectively, which shows the twist of adjacent dinitromethyl groups is caused by the steric effect. The strong hydrogen-bond interactions are presented between ammonium and nitro groups (Fig. 2b). The details of donor–acceptor distance are given in the ESI.^† Many studies have shown that the hydrogen-bonds enhance the stability of energetic molecules. At the molecular level, intermolecular hydrogen bonds between hydrazine cation and nitro groups play an important role in stabilizing energetic compounds. This kind of hydrogen-bonding interaction and cation–anion contact in the energetic salt is suggested as part of the explanation for closer packing, which causes the good density. As seen in Fig. 2c, the tetranitroethide anions are found in cross-stacking arrangements and layer by layer. While the hydrazine cation in the crystal, as the adhesive between the bricks, help to create a better stacking arrangement.Open in a separate windowFig. 2(a) Molecular structure of 5; (b) hydrogen-bonding interactions of 5 between hydrazine cation and tetranitroethide anion; (c) packing diagram of 5 (unit cell viewed along the b axis).The physical properties and calculated detonation performances are summarized in 20 Compound 5 has a detonation velocity of 9508 m s⁻¹ and a detonation pressure of P: 37.9 GPa, which is better than RDX (8748 m s⁻¹; 34.9 GPa) and similar to HMX (9320 m s⁻¹; 39.5 GPa). The sensitivities to impact and friction are 1.25 J and 34 N, respectively.Physical properties of dihydrazine tetranitroethide 5 and comparison with ADN, RDX and HMX

Two-dimensional aluminum phosphide semiconductor with tunable direct band gap for nanoelectric applications

More and more attractive applications of two-dimensional (2D) materials in nanoelectronic devices are being achieved successfully, which promotes the rapid and extensive development of new 2D materials. In this work, the structural and electronic properties of the V structure aluminum phosphide (V-AlP) monolayer are examined by density functional calculations, and its electronic properties under strain and an electric field are also explored in detail. The computation results indicate that it has good stability. Interestingly, it possesses a wide direct gap (2.6 eV), and its band gap exhibits a rich behavior depending on the strain, E-field and layer stacking. Under biaxial strain, its band gap can be tuned from 1 eV to 2.6 eV. And a direct-indirect band gap transition is found when external tension is applied. The V-AlP monolayer also exhibits anisotropic behavior as its band structure variation trends under strains along different directions are obviously different. When the external E-field is changed from 0.5 V Å⁻¹ to 1 V Å⁻¹, the band gap of the V-AlP monolayer can be tuned linearly from 0 eV to 2.6 eV. Layer stacking narrows the band gap of the 2D V-AlP material. It is concluded that strain, E-field and layer stacking can all be used effectively to modify the electronic property of the V-AlP monolayer. Thus, these results indicate that the V-AlP monolayer will have promising applications in nanoelectric devices.

More and more attractive applications of two-dimensional (2D) materials in nanoelectronic devices are being achieved successfully, which promotes the rapid and extensive development of new 2D materials.