New Suggestion of Highly Durable Electrode Design for Ordered Mesoporous Ni-Mn Binary Transition Metal Oxide Anode Material in Lithium-Ion Batteries.

Anode materials storing large-scale lithium ions gradually decrease electrochemical performance due to severe volume changes during cycling. Therefore, there is an urgent need to develop anode materials with high electrochemical capacity and durability, without deterioration arising due to the volume changes during the electrochemical processes. To date, mesoporous materials have received attention as anode materials due to their ability to mitigate volume expansion, offer a short pathway for Li+ transport, and exhibit anomalous high capacity. However, the nano-frameworks of transition metal oxide collapse during conversion reactions, demanding an improvement in nano-framework structure stability. In this study, ordered mesoporous nickel manganese oxide (m-NMO) is designed as an anode material with a highly durable nanostructure. Interestingly, m-NMO showed better cycle performance and higher electrochemical capacity than those of nickel oxide and manganese oxide. Operando small-angle X-ray scattering and ex situ transmission electron microscopic results confirmed that the binary m-NMO sustained a highly durable nanostructure upon cycling, unlike the single metal oxide electrodes where the mesostructures collapsed. Ex situ X-ray absorption spectroscopy proved that nickel and manganese showed different electrochemical reaction voltages, and thus undergoes sequential conversion reactions. As a result, both elements can act as complementary nano-propping buffers to maintain stable mesostructure.

Micro-structural analysis of NiFe2O4 nanoparticles synthesized by thermal plasma route and its suitability for BSA adsorption.

The paper presents the experimental studies pertaining to the adsorption of bovine serum albumin (BSA) on the nanoparticles of nickel ferrite (NiFe2O4) with a view of correlating the adsorption properties to their microstructure and zeta potentials. Physical properties of two kinds of nickel ferrites, one synthesized by thermal plasma route and the other by chemical co-precipitation method, are compared. Maximum adsorption (231.57 µg/mg) of BSA onto nickel ferrite nanoparticles, at body temperature (37 °C) was observed at pH-value of 5.58 for the thermal plasma synthesized particles showing its higher adsorption capacity than those synthesized by wet chemical means (178.71 µg/mg). Under the same physical conditions the value of zeta potential, obtained for the former, was higher than that of the latter over a wide range of pH values (3.64-9.66). This is attributed to the differences in the specific surface energies of the two kinds of nanoparticles arising from the degree of crystallinity. The paper presents the experimental evidence for the single crystalline nature of the individual nanoparticles, with mean size of 32 nm, for the thermal plasma synthesized particles as evidenced from the high resolution transmission electron microscopy and electron diffraction analysis. The measurements also reveal the poor crystalline morphology in the chemically prepared particles (mean size of 28 nm) although the X-ray diffraction patterns are not much different. The atomic force microscopy images confirm that the surfaces of plasma synthesized nanoparticles possesses higher surface roughness than that of chemically synthesized one. Presence of adsorbed protein was confirmed by vibrational spectroscopy. The Langmuir adsorption model is found to fit into the experimental data better than the Freundlich adsorption model.

Co(II)-Cu(II) mixed-oxide catalysts for single-step synthesis of 2,4,5-triaryl-1H-imidazole derivatives under microwave irradiation.

In this study, a catalyst composite of Co-Cu was prepared from chloride-containing precursor of Co(II) and Cu(II) metals using the milky latex of the Euphorbia neriifolia plant following green principles of synthesis. The catalyst composite was characterized using XRD, EDAX, SEM, HR-TEM, FTIR, XPS and TOF-MS. The crystallinity of the mixed-oxide composite with a distorted octahedral nature was confirmed from analysis. Chemical charge analysis of the Co-Cu mixed phase based on XPS revealed Co2+ and Cu2+ oxidation states. This material was used for synthesizing 2,4,5-triaryl-1H-imidazole (TIMDZOL) derivatives. Analysis of reaction conditions revealed that EtOH : PEG at 8 : 2 ratio under microwave conditions showed better yields with less time and better reusability of the Co-Cu catalyst.

Facile Synthesis of Mesoporous Nanohybrid Two-Dimensional Layered Ni-Cr-S and Reduced Graphene Oxide for High-Performance Hybrid Supercapacitors.

This study describes the single-step synthesis of a mesoporous layered nickel-chromium-sulfide (NCS) and its hybridization with single-layered graphene oxide (GO) using a facile, inexpensive chemical method. The conductive GO plays a critical role in improving the physicochemical and electrochemical properties of hybridized NCS/reduced GO (NCSG) materials. The optimized mesoporous nanohybrid NCSG is obtained when hybridized with 20% GO, and this material exhibits a very high specific surface area of 685.84 m2/g compared to 149.37 m2/g for bare NCS, and the pore diameters are 15.81 and 13.85 nm, respectively. The three-fold superior specific capacity of this optimal NCSG (1932 C/g) is demonstrated over NCS (676 C/g) at a current density of 2 A/g. A fabricated hybrid supercapacitor (HSC) reveals a maximum specific capacity of 224 C/g at a 5 A/g current density. The HSC reached an outstanding energy density of 105 Wh/kg with a maximum power density of 11,250 W/kg. A 4% decrement was observed during the cyclic stability study of the HSC over 5000 successive charge-discharge cycles at a 10 A/g current density. These results suggest that the prepared nanohybrid NCSG is an excellent cathode material for gaining a high energy density in an HSC.

Layer-by-layer nanohybrids of Ni-Cr-LDH intercalated with 0D polyoxotungstate for highly efficient hybrid supercapacitor.

The layer-by-layer mesoporous nanohybrids of Ni-Cr-layered double hydroxide (Ni-Cr-LDH) and polyoxotungstate nanoclusters (Ni-Cr-LDH-POW) are prepared via exfoliation reassembling strategy. The intercalative hybridization of Ni-Cr-LDH with POW nanoclusters leads to forming a layer-by-layer stacking framework with significant expansion of the interplanar spacing and surface area. The aqueous hybrid supercapacitor (AHSC) and all-solid-state hybrid supercapacitor (SSHSC) devices are fabricated using Ni-Cr-LDH-POW nanohybrid as a cathode and reduced graphene oxide (rGO) as an anode material. Notably, the NCW-2//rGO AHSC device delivers an ED of 43 Wh kg-1 at PD of 1.33 kW kg-1 and excellent electrochemical stability over 10,000 charge-discharge cycles. Moreover, NCW-2//rGO SSHSC exhibits an ED of 34 Wh kg-1 at PD of 1.32 kW kg-1 with capacitance retention of 86% after 10,000 cycles. These results highlight the excellent electrochemical functionality and advantages of the Ni-Cr-LDH-POW nanohybrids as a cathode for hybrid supercapacitors.

Highly Uniform Atomic Layer-Deposited MoS2@3D-Ni-Foam: A Novel Approach To Prepare an Electrode for Supercapacitors.

This article takes an effort to establish the potential of atomic layer deposition (ALD) technique toward the field of supercapacitors by preparing molybdenum disulfide (MoS2) as its electrode. While molybdenum hexacarbonyl [Mo(CO)6] serves as a novel precursor toward the low-temperature synthesis of ALD-grown MoS2, H2S plasma helps to deposit its polycrystalline phase at 200 °C. Several ex situ characterizations such as X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and so forth are performed in detail to study the as-grown MoS2 film on a Si/SiO2 substrate. While stoichiometric MoS2 with very negligible amount of C and O impurities was evident from XPS, the XRD and high-resolution transmission electron microscopy analyses confirmed the (002)-oriented polycrystalline h-MoS2 phase of the as-grown film. A comparative study of ALD-grown MoS2 as a supercapacitor electrode on 2-dimensional stainless steel and on 3-dimensional (3D) Ni-foam substrates clearly reflects the advantage and the potential of ALD for growing a uniform and conformal electrode material on a 3D-scaffold layer. Cyclic voltammetry measurements showed both double-layer capacitance and capacitance contributed by the faradic reaction at the MoS2 electrode surface. The optimum number of ALD cycles was also found out for achieving maximum capacitance for such a MoS2@3D-Ni-foam electrode. A record high areal capacitance of 3400 mF/cm2 was achieved for MoS2@3D-Ni-foam grown by 400 ALD cycles at a current density of 3 mA/cm2. Moreover, the ALD-grown MoS2@3D-Ni-foam composite also retains high areal capacitance, even up to a high current density of 50 mA/cm2. Finally, this directly grown MoS2 electrode on 3D-Ni-foam by ALD shows high cyclic stability (>80%) over 4500 charge-discharge cycles which must invoke the research community to further explore the potential of ALD for such applications.

Nanoflake-Modulated La2 Se3 Thin Films Prepared for an Asymmetric Supercapacitor Device.

La2 Se3 nanoflakes were prepared from an aqueous medium by means of a chemical-bath deposition method and were later utilized as a supercapacitor electrode. X-ray diffraction (XRD), Fourier transform Raman (FT Raman), field-emission scanning electron microscopy (FESEM), and contact-angle measurement techniques were used to study the structural, morphological, and wettability properties of La2 Se3 films. The XRD study confirmed the cubic crystal structure of the La2 Se3 film. The surface morphology and wettability studies revealed the nanoflake morphology with a hydrophilic surface, which could be beneficial to electrochemical reactions. The electrochemical performance of the La2 Se3 nanoflakes was evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. The La2 Se3 nanoflake electrode exhibited a maximum specific capacitance of 331 F g-1 at a scan rate of 5 mV s-1 . An electrochemical impedance study confirmed that the La2 Se3 nanoflake electrode has a better supercapacitive behavior in an aqueous electrolyte. The asymmetric supercapacitor device based on the La2 Se3 electrode in aqueous electrolyte exhibited good specific capacitance, excellent charge/discharge properties, and superior long-term cycling stability.