In situ metal organic framework (ZIF-8) and mechanofusion-assisted MWCNT coating of LiFePO/C composite material for lithium-ion batteries

LiFePO4 is one of the industrial, scalable cathode materials in lithium-ion battery production, due to its cost-effectiveness and environmental friendliness. However, the electrochemical performance of LiFePO4 in high current rate operation is still limited, due to its poor ionic- and electron-conductive properties. In this study, a zeolitic imidazolate framework (ZIF-8) and multiwalled carbon nanotubes (MWCNT) modified LiFePO4/C (LFP) composite cathode materials were developed and investigated in detail. The ZIF-8 and MWCNT can be used as ionic- and electron-conductive materials, respectively. The surface modification of LFP by ZIF-8 and MWCNT was carried out through in situ wet chemical and mechanical alloy coating. The as-synthesized materials were scrutinized via various characterization methods, such as XRD, SEM, EDX, etc., to determine the material microstructure, morphology, phase, chemical composition, etc. The uniform and stable spherical morphology of LFP composites was obtained when the ZIF-8 coating was processed by the agitator [A], instead of the magnetic stirrer [MS], condition. It was found that the (optimum of) 2 wt.% ZIF-8@LFP [A]/MWCNT composite cathode material exhibited outstanding improvement in high-rate performance; it maintained the discharge capacities of 125 mAh g−1 at 1C, 110 mAh g−1 at 3C, 103 mAh g−1 at 5C, and 91 mAh g−1 at 10C. Better cycling stability with capacity retention of 75.82% at 1C for 100 cycles, as compared to other electrodes prepared in this study, was also revealed. These excellent results were mainly obtained because of the improvement of lithium-ion transport properties, less polarization effect, and interfacial impedance of the LFP composite cathode materials derived from the synergistic effect of both ZIF-8 and MWCNT coating materials

A simple and flexible enzymatic glucose biosensor using chitosan entrapped mesoporous carbon nanocomposite

A flexible and promising amperometric glucose biosensor was reported using direct immobilization of glucose oxidase (GOx) on chitosan supported mesoporous carbon (MPC-CHT) nanocomposite. The availability of more functional groups particularly amine groups, the CHT was selected as an immobilization matrix as well as cross linker for GOx. The MPC-CHT-GOx composites were characterized well and discussed in details. The MPC-CHT-GOx modified electrode accelerates fast electron transfer on the electrode surface due to the excellent intermolecular interaction between the CHT and GOx molecule. Besides, the MPC-CHT-GOx composite showed well-defined redox behavior with enhanced direct electron transfer (DET) of GOx in PBS, pH 7. Amperometric response of MPC-CHT-GOx modified electrode displayed a good linear response over the glucose concentration ranges from 250 mu M to 3 mM with a detection limit (LOD) and sensitivity of 4.1 mu M and 56.12 mu A mM(-1) cm(-2), respectively. The MPC-CHT-GOx modified electrode also displayed good charge transfer coefficient (alpha) and heterogeneous rate constant (k(s)) values are 0.56 and 2.2182 s(-1). Besides, the MPC-CHT-GOx modified electrode exhibited good bio-catalytic activity with the Michaelis-Menten saturation (K-m(app)) value was about 2.14 mM. The practicability of the sensor was evaluated in biological real samples with satisfactory recoveries

Ruthenium Nanoparticles Decorated Tungsten Oxide as a Bifunctional Catalyst for Electrocatalytic and Catalytic Applications

The syntheses of highly stable ruthenium nanoparticles supported on tungsten oxides (Ru-WO₃) bifunctional nanocomposites by means of a facial microwave-assisted route are reported. The physicochemical properties of these Ru-WO₃ catalysts with varied Ru contents were characterized by a variety of analytical and spectroscopic methods such as XRD, SEM/TEM, EDX, XPS, N₂ physisorption, TGA, UV–vis, and FT-IR. The Ru-WO₃ nanocomposite catalysts so prepared were utilized for electrocatalytic of hydrazine (N₂H₄) and catalytic oxidation of diphenyl sulfide (DPS). The Ru-WO₃-modified electrodes were found to show extraordinary electrochemical performances for sensitive and selective detection of N₂H₄ with a desirable wide linear range of 0.7–709.2 μM and a detection limit and sensitivity of 0.3625 μM and 4.357 μA μM^–1 cm^–2, respectively, surpassing other modified electrodes. The modified GCEs were also found to have desirable selectivity, stability, and reproducibility as N₂H₄ sensors, even for analyses of real samples. This is ascribed to the well-dispersed metallic Ru NPs on the WO₃ support, as revealed by UV–vis and photoluminescence studies. Moreover, these Ru-WO₃ bifunctional catalysts were also found to exhibit excellent catalytic activities for oxidation of DPS in the presence of H₂O₂ oxidant with desirable sulfoxide yields

Unveiling the redox electrochemistry of 1D, urchin-like vanadium sulfide electrodes for high-performance hybrid supercapacitors

Exploring novel versatile electrode materials with outstanding electrochemical performance is the key to the development of advanced energy conversion and storage devices. In this work, we aim to construct new-fangled one-dimensional (1D) quasi-layered patronite vanadium tetrasulfide (VS4) nanostructures by using different sulfur sources, namely thiourea, thioacetamide, and L-cysteine through an ethyleneaminetetraacetic-acid (EDTA)-mediated solvothermal process. The as-prepared VS4 exhibits several unique morphologies such as urchin, fluffy nanoflower, and polyhedron with appropriate surface areas. Among the prepared nanostructures, the VS4-1@NF nanostructure exhibited excellent electrochemical properties in 6 M KOH solution, and we explored its redox electrochemistry in detail. The as-prepared VS4-1@NF electrode exhibited battery-type redox characteristics with the highest capacity of 280 C g-1 in a three-electrode assembly. Moreover, it offered a capacity of 123 F g-1 in a hybrid two-electrode set-up at 1 A g-1 with the highest specific energy and specific power of 38.5 W h kg-1 and 750 W kg-1, respectively. Furthermore, to ensure the practical applicability and real-world performance of the prepared hybrid AC@NF//VS4-1@NF cell, we performed a cycling stability test with more than 5,000 galvanostatic charge-discharge cycles at 2 A g-1, and the cell retained around 84.7% of its capacitance even after 5,000 cycles with a CE of 96.1%.This work was supported by the Research Program of Dongguk University in 2022 (No. S-2022-G0001-00016).Scopu

Graphene Nanosheet-Wrapped Mesoporous La0.8Ce0.2Fe0.5Mn0.5O3 Perovskite Oxide Composite for Improved Oxygen Reaction Electro-Kinetics and Li-O2 Battery Application

A novel design and synthesis methodology is the most important consideration in the development of a superior electrocatalyst for improving the kinetics of oxygen electrode reactions, such as the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in Li-O2 battery application. Herein, we demonstrate a glycine-assisted hydrothermal and probe sonication method for the synthesis of a mesoporous spherical La0.8Ce0.2Fe0.5Mn0.5O3 perovskite particle and embedded graphene nanosheet (LCFM(8255)-gly/GNS) composite and evaluate its bifunctional ORR/OER kinetics in Li-O2 battery application. The physicochemical characterization confirms that the as-formed LCFM(8255)-gly perovskite catalyst has a highly crystalline structure and mesoporous morphology with a large specific surface area. The LCFM(8255)-gly/GNS composite hybrid structure exhibits an improved onset potential and high current density toward ORR/OER in both aqueous and non-aqueous electrolytes. The LCFM(8255)-gly/GNS composite cathode (ca. 8475 mAh g−1) delivers a higher discharge capacity than the La0.5Ce0.5Fe0.5Mn0.5O3-gly/GNS cathode (ca. 5796 mAh g−1) in a Li-O2 battery at a current density of 100 mA g−1. Our results revealed that the composite’s high electrochemical activity comes from the synergism of highly abundant oxygen vacancies and redox-active sites due to the Ce and Fe dopant in LaMnO3 and the excellent charge transfer characteristics of the graphene materials. The as-developed cathode catalyst performed appreciable cycle stability up to 55 cycles at a limited capacity of 1000 mAh g−1 based on conventional glass fiber separators

Binder-free ultra-thin graphene oxide as an artificial solid electrolyte interphase for anode-free rechargeable lithium metal batteries

The unregulated growth of lithium dendrite upon cycling is hampering the applications of lithium metal batteries. The inherent artificial solid electrolyte interphase (SEI) formed during the first few cycles cannot provide the desired stability of lithium deposition. In the anode free battery (AFB) configuration, uncontrolled lithium plating on bare copper imposes a more serious lithium dendrite growth. Herein, we modify the copper current collector with a binder-free ultra-thin spin-coated graphene oxide (GO). The synchronize smooth and conductive GO-coated artificial SEI with lithium fluoride derived from fluoroethylene carbonate (FEC) electrolyte additive greatly control the lithium deposition. Accordingly, the synergistic effect enables smooth, uniform, and dendrite-free lithium plating. Moreover, the AFB with GO film and 5% FEC in the carbonate-based electrolyte is capable of achieving high coulombic efficiency of an average 98% and attains ~44% of its initial capacity after 50 cycles. In contrast, the full cell with bare Cu//LiNi1/3Mn1/3Co1/3O2 (NMC) has a coulombic efficiency of 89% and retains 26.9% after 20 cycles. Our results demonstrate that the synergy of GO-coated artificial SEI with FEC additive can be a promising approach to impede lithium dendrites growth and result in enhanced electrochemical performance in an AFB