Facile synthesis of ZnS/MnS nanocomposites for supercapacitor applications

Improved electrochemical performance of defect-induced supercapacitor electrodes based on MnS-incorporated MnO2 nanorods

In this paper, we report the effect of MnS nanoparticles on the electrochemical performance of 1D-MnO2 stable nanorods for supercapacitor electrodes. The MnS-incorporated 1D-MnO2 (MnO2/MnS) nanorods were produced using a facile two-step hydrothermal method. Morphological investigation reveals that the incorporation of MnS nanoparticles distorts the lattice fringes and extends the interlayer spacing of the MnO2 nanorods. The structural study showed that MnS modified the structural parameters of the nanocomposite. XPS analysis revealed defects in the nanocomposite due to the generation of oxygen vacancies. The MnO2/MnS nanocomposite improves capacitive performance and has the highest specific capacitance of 305 F g-1, at a current density of 1 A g-1 with an energy density of 5.7 W h kg-1 and a power density of 449 W kg-1. The MnO2/MnS nanocomposite electrodes exhibit exceptional cyclic stability after 5000 charging and discharging cycles. With enhanced specific capacitance and excellent cyclic stability, the MnO2/MnS nanocomposite paves a new way to produce supercapacitor electrodes.

Selective Anchoring by Surface Sulfur Species Coupled with Rapid Interface Electron Transfer for Ultrahigh Capacity Extraction of Uranium from Seawater

Improving the adsorption selectivity, enhancing the extraction capacity, and ensuring the structural stability of the adsorbent are the key to realize the high efficiency recovery of uranium. In this work, we utilized the strong Lewis acid-base interaction between S2- and U(VI)O22+ coupling rapid electron transfer at the MnS/U(VI)O22+ solid-liquid interface to achieve excellent selectivity, high adsorption capacity, and rapid extraction of uranium. The as-synthesized MnS adsorbent exhibited an ultrahigh uranium extraction capacity (2457.05 mg g-1) and a rapid rate constant (K = 9.11 × 10-4 g h-1 mg-1) in seawater with 100.7 ppm of UO2(NO3)2 electrolyte. The kinetic simulation reveals that this adsorption process is a chemical adsorption process and conforms to a pseudo-second-order kinetic model, indicating electron transfer at the MnS/U(VI)O22+ solid-liquid interface. The relevant (quasi) in situ spectroscopic characterization and theoretical calculation results further revealed that the outstanding uranium extraction property of MnS could be attributed to the highly selective UO22+ adsorption of MnS with lower adsorption energy as a result of the strong interaction between S2- and UO22+ and the rapid mass transfer and interface electron transfer from S2- and low-valent Mn(II) to U(VI)O22+.

Three-dimensional ternary NixCuyZnz(CO3)(OH)2 electrodes for supercapacitors: electrochemical properties and applications

Transition metal-based binary and ternary compound arrays were directly grown on a porous Ni foam substrate using a facile one-step hydrothermal method. Transition metals are considered ideal electrode materials for faradaic capacitors because they exhibit a wide range of oxidation states enabling effective redox charge transfer. Furthermore, compounds in which two or more transition metals react can help increase the number of active sites for charge-discharge reactions and provide more valence changes for improved charge transfer. In this work, we fabricated ternary electrodes with Ni, Cu, and Zn ions, exhibiting a larger surface area and higher entropy than those made with binary compounds. The Ni_xCu_yZn_z-based ternary electrode had a shorter diffusion path for the electrolyte ions owing to its larger surface area. Ternary compounds can increase the entropy of the electrode because of the reaction between atoms of different sizes, bringing about a synergistic effect for high characteristic electrochemical values. The optimized Ni_xCu_yZn_z(CO₃)(OH)₂ compound showed a maximum specific capacity of 344 mA h g^-1 at a current density of 3 A g^-1, which was remarkably higher than that of the binary electrode, and a cycling stability of 84.9% after 5000 cycles. An asymmetric supercapacitor produced with this compound as the positive electrode and graphene as the negative electrode exhibited a high energy density of 36.2 W h kg^-1 at a power density of 103.1 W kg^-1 and a current density of 2 A g^-1. The asymmetric supercapacitor fabricated using the Ni_xCu_yZn_z(CO₃)(OH)₂ compound as the positive electrode exhibited excellent electrical properties when used in an illuminated LED device.

Novel application of sodium manganese oxide in removing acidic gases in ambient conditions

In this study, we have demonstrated the application of sodium manganese oxide for the chemisorption of toxic acidic gases at room temperature. The fabricated alkali ceramic has Na_0.4MnO₂, Na₂Mn₃O₇, and Na_xMnO₂ phases with a surface area of 2.6 m² g^-1. Na-Mn oxide was studied for oxidation of H₂S, SO₂, and NO₂ gases in the concentration range of 100-500 ppm. The material exhibited a high uptake capacity of 7.13, 0.75, and 0.53 mmol g^-1 for H₂S, SO₂, and NO₂ in wet conditions, respectively. The material was reusable when regenerated simply by soaking the spent oxide in a NaOH-H₂O₂ solution. While the H₂S chemisorption process was accompanied by sulfide, sulfur, and sulfate formation, the SO₂ chemisorption process yielded only sulfate ions. The NO₂ chemisorption process was accomplished by its conversion to nitrite and nitrate ions. Thus, the present work is one of the first reports on alkali ceramic utilization for room-temperature mineralization of acidic gases.

Binder-free cupric-ion containing zinc sulfide nanoplates-like structure for flexible energy storage devices

Researchers have been enthusiastic about developing high-performance electrode materials based on metal chalcogenides for energy storage applications. Herein, we developed cupric ion-containing zinc sulfide (ZnS:Cu) nanoplates by using a solvothermal approach. The as-synthesized ZnS:Cu nanoplates electrode was characterized and analyzed by using XRD, SEM, TEM, EDS, and XPS. The binder-free flexible ZnS:Cu nanoplates exhibited excellent specific capacitance of 545 F g-1 at a current density of 1 A g-1. The CV and GCD measurements revealed that the specific capacitance was mainly attributed to the Faradaic redox mechanism. Further, the binder-free flexible ZnS:Cu nanoplates electrode retained 87.4% along with excellent Coulombic efficiency (99%) after 5000 cycles. The binder-free flexible ZnS:Cu nanoplates exhibited excellent conductivity, specific capacitance, and stability which are beneficial in energy storage systems. These findings will also open new horizons amongst material scientists toward the new direction of electrode development.

Wet-chemical assisted synthesis of MnSe/ZnO nanostructures as low-resistance robust novel cathode material for advanced hybrid supercapacitors

We proposed a novel MnSe–ZnO-based binary nanocomposite synthesized via a wet-chemical assisted method which deliver high power and energy densities, suppressing previous reports on MnSe and ZnO with decent cycling durability with good rate performance.

High electrochemical performance of ink solution based on manganese cobalt sulfide/reduced graphene oxide nano-composites for supercapacitor electrode materials

Large scale supercapacitor electrodes were prepared by 3D-printing directly on a graphite paper substrate from ink solution containing manganese cobalt sulfide/reduced graphene oxide (MCS/rGO) nanocomposites. The MCS/rGO composite solution was synthesized through the dispersion of MCS NPs and rGO in dimethylformamide (DMF) solvent at room temperature. Their morphology and composition were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray diffraction (EDS). The role of rGO on decreasing charge transfer resistance and enhancing ion exchange was discussed. The MCS/rGO electrode exhibits an excellent specific capacitance of 3812.5 F g⁻¹ at 2 A g⁻¹ and it maintains 1780.8 F g⁻¹ at a high current density of 50 A g⁻¹. The cycling stability of the electrodes reveals capacitance retention of over 92% after 22 000 cycles at 50 A g⁻¹.

Large scale supercapacitor electrodes were prepared by 3D-printing directly on a graphite paper substrate from ink solution containing manganese cobalt sulfide/reduced graphene oxide (MCS/rGO) nanocomposites.

Construction of Various One-Dimensional ZnS/MnS Heteronanostructures with Varied Diameters via the Multistep Solution-Solid-Solid Growth Method

A series of novel one-dimensional (1D) ZnS/MnS heteronanostructures were prepared by a multistep solution-solid-solid (SSS) growth method using [(C₄H₉)₂NCS₂]₂Zn and [(C₄H₉)₂NCS₂]₂Mn as the precursors and Ag₂S as the catalyst. The composition of the 1D heteronanostructures could be effectively modulated by varying the addition sequence of the precursors, such as the Ag₂S/MnS/ZnS and Ag₂S/ZnS/MnS heteronanostructures, which were obtained through the successive addition of [(C₄H₉)₂NCS₂]₂Zn and [(C₄H₉)₂NCS₂]₂Mn precursors but in different sequences. Using the same Ag₂S catalysts, the average diameter of the 1D ZnS/MnS heteronanostructures with multisegments of ZnS and MnS is located between that of ZnS nanorod in Ag₂S/ZnS and that of MnS nanorod in Ag₂S/MnS. This phenomenon could arise from the different cationic radii and lattice parameters of ZnS and MnS. The UV-vis absorbance of the 1D ZnS/MnS heteronanostructures could be attributed to the interband transitions of ZnS and MnS. These findings contribute to the rational synthesis of novel 1D semiconductor heteronanostructures with multicomponents and benefit the development of optoelectronic devices.

In-Situ Growth of Urchin Manganese Sulfide Anchored Three-Dimensional Graphene (γ-MnS@3DG) on Carbon Cloth as a Flexible Asymmetric Supercapacitor

In energy storage-device it is highly crucial to develop durable electrode materials having high specific capacitance and superior energy density without disturbing its inherent flexibility. Herein, we demonstrate three-dimensional graphene oxide decorated monodispersed hollow urchin γ-MnS (γ-MnS@3DG) via proficient one-step solvothermal method. The designed material delivers a remarkable capacitance of 858 F g^-1 at 1 A g^-1. A flexible solid state asymmetric supercapacitor (ASCs) device assembled using surface activated carbon cloth (CC) decorated with γ-MnS@3DG as positive and three-dimension graphene on carbon cloth (3DG@CC) as negative electrode, (γ-MnS@3DG//3DG). The device delivers 26 Wh kg^-1 energy density at power density 500 W kg^-1 @ 1A g^-1 and retains favorable energy density 17.8 Wh kg^-1 at an ultrahigh power density of 1500 W kg^-1@3 A g^-1. This carbon embedded transition-metal sulfide (TMS) based ASC demonstrates eminent mechanical flexibility under rigorous bending states maintaining invariant performance.

Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

Synthesis of zinc sulfide/copper sulfide/porous carbonized cotton nanocomposites for flexible supercapacitor and recyclable photocatalysis with high performance

The composite material composed of zinc sulfide, copper sulfide and porous carbon is prepared in this study, exhibiting excellent performances in the field of supercapacitor electrode and photocatalysts. In the degradation process of organic pollutants, zinc sulfide/copper sulfide with heterostructure effectively reduce the recombination rate of photo-generated electron-hole pairs. And the porous carbon substrate can not only accelerate the separation of photo-carriers but also provide numerous active sites. Furthermore, the sample can be easily separated after decomposing the organic pollutants. As a supercapacitor electrode, the combination of zinc sulfide/copper sulfide with large pseudo-capacitance and porous carbon material with excellent double-layercapacitance results in superior electrochemical performances. The composite electrode shows a high specific capacitance of 1925 mF cm^-2/0.53 mAh cm^-2 at 4 mA cm^-2. And the symmetric flexible supercapacitor based on the composite electrode achieves an outstanding energy density (0.39 Wh cm^-2 at the power density of 4.32 W cm^-2). Therefore, the zinc sulfide/copper sulfide/porous carbonized cotton nanocomposites (pCZCS) prepared herein exhibit dual functions of photocatalysts with high efficiency as well as energy storage materials with high energy density, which is interesting and important for expanding the practical applications in cross fields.

Synthesis of MnO2 nanostructures with MnS-deposits for high performance supercapacitor electrodes

We report the synthesis of MnO₂ nanostructures with MnS deposits via a facile one-step hydrothermal process for high-performance supercapacitor applications.