Wells-Dawson Arsenotungstate Porous Derivatives for Electrochemical Supercapacitor Electrodes and Electrocatalytically Active Materials

Tailoring the Coordination Microenvironment of Polymolybdate within a Metal-Organic Coordination System for Enhanced Capacitive Activity

The design of a low-cost and efficient electrode material is crucial for electrochemical energy storage. Effectual utilization of polymolybdate as an electrode material for a supercapacitor is promising. Meanwhile, the coordination microenvironments of polymolybdate sho potential effects on its performance. Herein, we designed and synthesized four polymolybdate-based metal-organic complexes using a structure design strategy. Their structures were characterized and analyzed using single crystallographic data. The theoretical calculations revealed that the coordination microenvironments of polymolybdate play a vital role in the hydrogen ions migration. High H adsorption capacity can obviously boost the electrochemical activity. The 1-based glassy carbon electrode showed the highest specific capacitance value of 1739.4 F·g-1 at the current density of 1 A·g-1. Meanwhile, the carbon cloth-based electrode fabricated by complex 1 (1/CC) also displayed a high capacitance performance. A hybrid supercapacitor was assembled using the 1/CC electrodes and showed a high energy density of 29.0 Wh kg-1 at the power density of 0.80 kW kg-1.

Design of a new nanocomposite based on Keggin-type [ZnW12O40]6- anionic cluster anchored on NiZn2O4 ceramics as a promising material towards the electrocatalytic hydrogen storage

Extensive research efforts have been dedicated to developing electrode materials with high capacity to address the increasing complexities arising from the energy crisis. Herein, a new nanocomposite was synthesized via the sol-gel method by immobilizing K6ZnW12O40 within the surface of NiZn2O4. ZnW12O40@NiZn2O4 was characterized by FT-IR, UV-Vis, XRD, SEM, EDX, BET, and TGA-DTG methods. The electrochemical characteristics of the materials were examined using cyclic voltammogram (CV) and charge-discharge chronopotentiometry (CHP) techniques. Multiple factors affecting the hydrogen storage capacity, including current density (j), surface area of the copper foam, and the consequences of repeated cycles of hydrogen adsorption-desorption were evaluated. The initial cycle led to an impressive hydrogen discharge capability of 340 mAh/g, which subsequently increased to 900 mAh/g after 20 cycles with a current density of 2 mA in 6.0 M KOH medium. The surface area and the electrocatalytic characteristics of the nanoparticles contribute to facilitate the formation of electrons and provide good diffusion channels for the movement of electrolyte ions throughout the charge-discharge procedure.

Deep oxidative desulfurization of gas oil by iron(III)-substituted polyoxometalate immobilized on nickel(II) oxide, ((n-C4H9)4N)4H[PW11FeO39]@NiO, as an efficient nanocatalyst

Sulfur compounds are among the most unfavorable constituents of petroleum derivatives, so stringent regulations have been established to curb their atmospheric emissions. In this regard, a new nanocomposite ((n-C4H9)4N)4H[PW11FeO39]@NiO) was synthesized composed of quaternary ammonium bromide salt of ironIII-substituted Keggin-type polyoxometalate immobilized on nickel(II) oxide nanoceramics via sol-gel method. The assembled (n-C4H9)4N)4H[PW11FeO39]@NiO nanocomposite was identified by FT-IR, UV-Vis, XRD, SEM, EDX, and TGA-DTG methods. The characterization results exhibited that ((n-C4H9)4N)4H[PW11FeO39] dispersed uniformly over the surface of the NiO nanoceramics. The ((n-C4H9)4N)4H[PW11FeO39]@NiO nanocomposite was employed as a heterogeneous nanocatalyst in the extractive coupled oxidation desulfurization (ECOD) of real gas oil and dibenzothiophene (DBT) as a model compound. Under relatively moderate conditions, the catalytic performance of the ((n-C4H9)4N)4H[PW11FeO39]@NiO in the ECOD procedure was studied by incorporating acetic acid/hydrogen peroxide as an oxidant system at a volume ratio of 1:2. According to the ECOD results, the ((n-C4H9)4N)4H[PW11FeO39]@NiO demonstrated the effectiveness of up to 95% with 0.1 g at 60 °C under optimal operating conditions. Moreover, the ((n-C4H9)4N)4H[PW11FeO39]@NiO nanocatalyst could be separated and reused for five runs without a noticeable decrease in the ECOD process. This study provides a promising way to meet the target of ultra-low sulfur as an essential process in oil refineries.

Nanomaterial with Core-Shell Structure Composed of {P2W18O62} and Cobalt Homobenzotrizoate for Supercapacitors and H2O2-Sensing Applications

Designing and preparing dual-functional Dawson-type polyoxometalate-based metal-organic framework (POMOF) energy storage materials is challenging. Here, the Dawson-type POMOF nanomaterial with the molecular formula CoK₄[P₂W₁₈O₆₂]@Co₃(btc)₂ (abbreviated as {P₂W₁₈}@Co-BTC, H₃btc = 1,3,5-benzylcarboxylic acid) was prepared using a solid-phase grinding method. XRD, SEM, TEM et al. analyses prove that this nanomaterial has a core-shell structure of Co-BTC wrapping around the {P₂W₁₈}. In the three-electrode system, it was found that {P₂W₁₈}@Co-BTC has the best supercapacitance performance, with a specific capacitance of 490.7 F g^-1 (1 A g^-1) and good stability, compared to nanomaterials synthesized with different feedstock ratios and two precursors. In the symmetrical double-electrode system, both the power density (800.00 W kg^-1) and the energy density (11.36 Wh kg^-1) are greater. In addition, as the electrode material for the H₂O₂ sensor, {P₂W₁₈}@Co-BTC also exhibits a better H₂O₂-sensing performance, such as a wide linear range (1.9 μM-1.67 mM), low detection limit (0.633 μM), high selectivity, stability (92.4%) and high recovery for the detection of H₂O₂ in human serum samples. This study provides a new strategy for the development of Dawson-type POMOF nanomaterial compounds.

Four Anderson-type [TeMo6O24]6−-based metal–organic complexes with a new bis(pyrimidine)-bis(amide): multifunctional electrochemical and adsorption performances

Four isostructural Anderson-type POM-based metal–organic complexes derived from a new bis(pyrimidine)-bis(amide) ligand were synthesized, showing multifunctional electrochemical sensing activities and good adsorption performances for organic dyes.

Two polymolybdate-directed Zn(ii) complexes tuned by a new bis-pyridine-bis-amide ligand with a diphenylketone spacer for efficient ampere sensing and dye adsorption

Two polymolybdate-based Zn(ii) complexes were constructed from a new bis-pyridine-bis-amide ligand, which can be used as electrocatalysts and electrochemical sensors for Cr(vi), KBrO3, H2O2 and AA, and exhibit selective adsorption of CV and MB.

{BW12O40} Hybrids Modified by in Situ Synthesized Rigid Ligand with Supercapacitance and Photocatalytic Properties

Organic rigid ligand-modified polyoxometalate-based materials possess complex and diverse structures, promising electrochemical energy storage properties and outstanding photocatalytic capabilities. Hence, two new [BW₁₂O₄₀]^5-(abbreviated as {BW₁₂O₄₀})-based inorganic-organic hybrids [{Cu(en)₂(H₂O)}][{Cu(pdc)(en)}{Cu(en)₂}(BW₁₂O₄₀)]·2H₂O (1) and [{Cu^I₅(pz)₆(H₂O)₄}(BW₁₂O₄₀)] (2) (pdc = 2-picolinate, en = ethylenediamine, pz = pyrazine) were successfully synthesized through a hydrothermal method. Among them, pdc and pz were obtained by in situ transformation from 2,6-pyridinedicarboxylic acid (H₂ pydc) and 2,3-pyrazinedicarboxylic acid (H₂pzdc), respectively. In compound 1, the {BW₁₂O₄₀} clusters as an intermediate junction connect with {Cu(pdc)(en)}{Cu(en)₂} and {Cu(en)₂(H₂O)} to form monomers, which in turn form supramolecular chains, sheets, and space network via hydrogen bonding. The {BW₁₂O₄₀} clusters are packed into copper-pyrazine frameworks in compound 2, and a unique polyoxometalate-based metal organic frameworks (POMOFs) structure with a new topology of {12}₂{6.12³.14²}₂{6².12.14².18}{6².12³.16}{6}₆ is formed via covalent bonds. When used as electrode materials for supercapacitors, the values of specific capacitance are 651.56 F g^-1 for 1-GCE and 584.43 F g^-1 for 2-GCE at a current density of 2.16 A g^-1 and good cycling stability (90.94%, 94.81% of the initial capacity after 5000 cycles at 15.12 A g^-1, respectively). The kinetic analysis reveals that surface capacitance plays a major role. Furthermore, both compounds can effectively degrade Rhodamine B (RhB) and Methylene blue (MB), showing the outstanding photocatalytic performance.