Latest ArticlesMoS2 is a typical electrocatalyst for hydrogen evolution reaction (HER), but the HER activity is spoilt by intensive adsorption towards H*, which requires further improvement. For n-type MoS2, the construction of p-n heterojunction with p-type MoO3 can reverse this situation, because inner electronic field in p-n heterojunction can facilitate H* desorption. Based on this hypothesis, p-n heterojunction is built between MoS2 and MoO3 with polyoxometalate compound as precursor. The obtained MoO3/MoS2 exhibits excellent HER activity, which only requires 68 mV to obtain 10 mA/cm2. With MoO3/MoS2 as cathode material and Zn slice as anode, Zn-H+ battery is assembled. Its open circuit voltage achieves 1.11 V with short circuit current 151.4 mA/cm2. The peak power density of this Zn-H+ battery reaches 47.6 mW/cm2. When discharge at 10 mA/cm2, the specific capacity and energy density reach 728 mAh/g and 759 Wh/kg. In this process, H2 production rate of Zn-H+ battery achieves 364 μmol/h with Faradic efficiency 97.8%. It realizes H2 production and electricity generation simultaneously.
The similarity of local structure-connection pattern and volumetrically compressive strain between host and guest phases can be used to stabilize heteroid metastable matter and tune the local structure and properties. Here a series of metastable ABO3 (A = Mn; B = Mn0.5Mo0.5, Mn1/3Ta2/3, and Mn0.5Ta0.5) were trapped in LiTaO3 to form solid-solutions, where the difference of solid solubility limit reveals the barrier of size effect on chemical pressure. All samples show antiferromagnetic characters, in which the (LiTaO3)1--[Mn(Mn0.5Mo0.5)O3] series exhibit more complex magnetic and dielectric behaviors with the increasing of metastable guest phase, stemming from the complex interactive mechanism between Mn2+ and Mo6+. The cell parameter variation of (LiTaO3)1--[Mn(Mn0.5Ta0.5)O3] shows a more regularly changing tendency, on account of the smallest size barrier. These findings show that chemical pressure can effectively stimulate the physical pressure to intercept and modulate a metastable phase at atomic-scale by compressibility effect between like structures at ambient pressure.
Available online two new Ni8Mo8 bimetallic coordination clusters, [Ni4(TC4A)]2[(Mo5ⅤMo3ⅥO24)(PO4)] (+Solvent) (Ni8PMo8, H4TC4A= p-tert-butylthiacalix[4]arene) and [Ni4(TC4A)]2[(Mo5ⅤMo3ⅥO24)(OH)(CO3)] (+Solvent) (Ni8Mo8), were synthesized by solvothermal method and structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, FT-IR spectroscopy, and TGA experiments, respectively. The usage of H3PMo12O40 as source for Ni8PMo8 resulted a sandwich like structure built from two Ni4-thiacalix[4]arene units and a Mo8 polyoxometalate with inner spaces of PO43−. Ni8Mo8 with the similar structure to that of Ni8PMo8 is from H2MoO4 starting reagent with OH− and CO32− anions encapsulated in the center. The two clusters can be directly loaded on carbon paper and utilized as working electrodes which showed distinguishable performances for glucose detection and oxidation. This work provides a better understanding of the structure–property relationships in using substituted polyoxometalates for electrochemical applications and is helpful for building calixarene-based or polyoxometalate-based functional materials.
Synthetic conditions and ligands are the key structural defining factors of metal–organic frameworks (MOFs). Therefore, reasonable optimization of these aspects is considered to be an effective means for designing materials with novel structures and target functions. Herein, two novel Co(Ⅱ)-based MOFs, namely [Co(HL)(dibp)]n (HL-8) and {[Co2(L)(OH)(dibp)]·DMA}n (HL-9) (H3L = 2′, 6′-dimethyl-[1,1′-biphenyl]-3,4′,5-tricarboxylic acid; dibp = 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl]), have been hydrothermally synthesized and structurally characterized. HL-8 crystallizes in the orthorhombic system (Pna21) with a grid layer structure, while HL-9 crystallizes in the monoclinic P21/n space group assembled through Co4(OH)2 clusters with organic ligands. Remarkably, benefiting from the finite cage-like structure, HL-9 exhibited enhanced performance in carbon dioxide (CO2) adsorption/catalytic transformation and excellent size selectivity during dye molecular adsorption process.
Gel polymer electrolytes (GPEs) are promising alternatives to liquid electrolytes applied in high-energy-density batteries. Here superior SiO2 nanofiber composite gel polymer electrolytes (SNCGPEs) are developed via in-situ ionic ring-opening polymerization of 1,3-dioxolane (DOL) monomers in SiO2 nanofiber membrane (PDOL-SiO2) for lithium metal batteries. The oxygen atoms of PDOL together with Si-O of SiO2 construct a more efficient channel for Li+ migration. Consequently, the lithium ion transference number (tLi+) and ionic conductivity (σ) at 30 ℃ of PDOL-SiO2 are 0.80 and 1.68 × 10−4 S/cm separately. PDOL-SiO2 manifests the electrochemical decomposition potentials of 4.90 V. At 0.5 mA/cm2, Li|PDOL-SiO2|Li cell shows a steady cycling performance for nearly 1400 h. LFP|PDOL-SiO2|Li battery can steadily cycle at 0.5 C with a capacity retention rate of 89% after 200 cycles. While cycling at 2 C, the capacity retention rate can maintain at 78% after 300 cycles. This contribution provides a innovative strategy for accelerating Li+ transportation via designing PDOL molecular chains throughout the SiO2 nanofiber framework, which is crucial for high-energy-density LMBs.
Potassium ion batteries (PIBs) have been regarded as promising alternatives to lithium ion batteries (LIBs) on account of their abundant resource and low cost in large scale energy storage applications. However, it still remains great challenges to explore suitable electrode materials that can reversibly accommodate large size of potassium ions. Here, we construct oxygen-deficient V2O3 nanoparticles encapsulated in amorphous carbon shell (Od-V2O3@C) as anode materials for PIBs by subtly combining the strategies of morphology and deficiency engineering. The MOF derived nanostructure along with uniform carbon coating layer can not only enables fast K+ migration and charge transfer kinetics, but also accommodate volume change and maintain structural stability. Besides, the introduction of oxygen deficiency intrinsically tunes the electronic structure of materials according to DFT calculation, and thus lead to improved electrochemical performance. When utilized as anode for PIBs, Od-V2O3@C electrode exhibits superior rate capability (reversible capacities of 262.8, 227.8, 201.5, 179.8, 156.9 mAh/g at 100, 200, 500, 1000 and 2000 mA/g, respectively), and ultralong cycle life (127.4 mAh/g after 1000 cycles at 2 A/g). This study demonstrates a feasible way to realize high performance PIBs through morphology and deficiency engineering.
The strong intrinsic Coulomb interactions of Frenkel excitons in crystalline carbon nitride (CCN) greatly limits their dissociation into electrons and holes, resulting in unsatisfactory charges separation and photocatalytic efficiency. Herein, we propose a strategy to facilitate excitons dissociation by molecular regulation induced built-in electric field (BIEF). The electron-rich pyrimidine-ring into CCN changes the charge density distribution over heptazine-rings to induce BIEF between melon chains. Such BIEF is sufficient to overcome the considerable exciton binding energy (EBE) and reduce it from 38.4 meV to 16.4 meV, increasing the excitons dissociation efficiency (EDE) from 21.5% to 51.9%. Our results establish a strategy to facilitate excitons dissociation through molecular regulation induced BIEF, targeting the intrinsic high EBE and low EDE of polymer photocatalysts.
Perovskite quantum dots (PQDs) possess remarkable optical properties, such as tunable photoluminescence (PL) emission spectra, narrow full width at half maximum (FWHM) and high PL quantum yield (QY), endowing the PQDs great application prospects. However, the inherent structural instability of PQDs has seriously hindered the application of PQDs in various photoelectric devices. In this work, a microfluidic electrospinning method was used to fabricate color-tunable fluorescent formamidinium lead halogen (FAPbX3, X = Cl, Br, I) PQDs/polymer core-shell nanofiber films. The core-shell spinning nanofiber not only supplies the interspace for the in-situ formation of PQDs, but also significantly reduces the permeability of moisture and oxygen in the air, which greatly improves the stability of PQDs. After adjusting the composition of precursors, the blue-emissive polystyrene (core) and polymethyl methacrylate (shell) coated FAPbCl3 QDs (abbreviated as PS/FAPbCl3/PMMA, hereinafter), green-emissive PS/FAPbBr3/PMMA and red-emissive PS/FAPbI3/PMMA nanofiber films were fabricated with the highest PL QY of 82.3%. Moreover, the PS/FAPbBr3/PMMA nanofiber film exhibits great PL stability under blue light irradiation, long-term storage in the air and water resistance test. Finally, the green- and red-emissive nanofiber films were directly applied as light conversion films to fabricate wide-color-gamut display with the color gamut of 125%, indicating their tremendous potentials in optoelectronic applications.
Based on the reported Fe clusters constructed by using N-tris(hydroxymethyl)methylglycine (H5thmmg), herein, we explored the use of H5thmmg for Ni chemistry. Successfully, an octanuclear Ni cluster, Ni8O(H3thmmg)6·2NO3 (Ni8) was acquired under solvothermal condition. Its metallic core is comprised of two centrosymmetric cubanes Ni4(µ3-O)3(µ6-O) linked by sharing an O2− ion and six H3thmmg2− ligands are attached to the periphery. Interestingly, the 2-mercapto-5-amino-1,3,4-thiadiazole (Hmat) ligand with both N and S donor atoms was introduced into the synthesis of Ni8 cluster, a disparate decanuclear nickel cluster, Ni10O(OH)2(H3thmmg)4(mat)8 (Ni10) is assembled by H3thmmg2− and mat− mixed ligands. The metal core of Ni10 cluster is a pudgy tetrahedron, whose four vertexes are four Ni2+ ions and the remanent six Ni2+ ions are located in the tetrahedral cavity. Four H3thmmg2− ligands are located at the four vertices of the tetrahedron and 8 mat− ligands are all on the six sides of the tetrahedron. The different synthetic conditions contribute to the different configurations. Magnetic studies indicate that both complexes Ni8 and Ni10 display antiferromagnetic interactions.
Na-CO2 batteries have attracted extensive attention due to their high theoretical energy density (1125 Wh/kg), efficient utilization of CO2, and abundant sodium resources. However, they are trapped by the sluggish decomposition kinetic of discharge products (mainly Na2CO3) on cathode side during the charging process. Here we prepared a series of nano-composites composed of RuO2 nanoparticles in situ loaded on activated multi-walled carbon nanotubes (RuO2@a-MWCNTs) through hydrolyzing reaction followed by calcination method and used them as cathode catalysts to accelerate the decomposition of Na2CO3. Among all catalysts, the RuO2@a-MWCNTs with appropriate ratio of RuO2 (49.7 wt%) demonstrated best stability and rate performance in Na-CO2 batteries, benefiting from both high specific surface area (160.3 m2/g) and highly dispersed RuO2 with ultrafine nanostructures (~2 nm). At a limited capacity of 500 mAh/g, Na-CO2 batteries could afford the operation of over 120 cycles at 100 mA/g, and even at the current density to 500 mA/g, the charge voltage was still lower than 4.0 V after 40 cycles. Further theoretical calculations proved that RuO2 was the catalytically active center and contributed to the decomposition of Na2CO3 by weakening the C=O bond. The synergetic functions of high specific surface (CNTs) and high catalytic activity (RuO2) will inspire more progress on metal-CO2 batteries.
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