Supercapacitors and triboelectric nanogenerators based on electrodes of greener iron nanoparticles/carbon nanotubes composites

The development of supporting materials based on carbon nanotubes (CNTs) impregnated with iron nanoparticles via a sustainable and green synthesis employing plant extract of Punica granatum L. leaves was carried out for the iron nanoparticle modification and the following impregnation into the carbon nanotubes composites (CNT-Fe) that were also coated with polypyrrole (CNT-Fe + PPy) for use as electrode for supercapacitor and triboelectric nanogenerators. The electrochemical characterization of the materials by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) assays revealed that the CNT-Fe + PPy gave rise to better performance due to the association of double-layer capacitance behavior of carbon derivative in association with the pseudocapacitance contribution of PPy resulting in an areal capacitance value 202 mF/ cm2 for the overall composite. In terms of the application of electrodes in triboelectric nanogenerators, the best performance for the composite of CNT-Fe + PPy was 60 V for output voltage and power density of 6 μW/cm2. The integrated system showed that the supercapacitors can be charged directly by the nanogenerator from 0 to 42 mV in 300 s. The successful green synthesis of iron nanoparticles on CNT and further PPy coating provides a feasible method for the design and synthesis of high-performance SCs and TENGs electrode materials. This work provides a systematic approach that moves the research front forward by generating data that underpins further research in self-powered electronic devices.

Engineered graphene quantum dot nanocomposite triggers α-synuclein defibrillation: Therapeutics against Parkinson's disease

Emerging clinically required α-synuclein (α-syn) inhibitor which acts as a neuroprotective nanocomposite drug is in increased demand as a patient-safe central nervous system therapeutic. This inhibitor is intended to chemically engineer graphene quantum dot (GQD) with blue luminescence, and stands to be a potential cure for Parkinson's disease. It has been theorized that α-syn aggregation is a critical step in the development of Parkinson's. Hence narrow the target by α-syn inhibition, through chemically synthesize methyl N-allyl N-benzoylmethioninate (MABM) and functionally engineer the surface of GQD to target the brain delivery on C57BL/6 mice. Spectroscopic and simulation studies confirm defibrillation through the interaction between N-terminal amino acids and MABM-GQD nanoparticles, which makes nontoxic α-syn. Therefore, this drug's ability to cross the blood-brain barrier in vitro functionally prevents neuronal loss in neuroblastoma cells. Thus, in vivo cerebral blood flow analysis using magnetic resonance imaging illustrates, how this nanocomposite can possibly treat Parkinson's.

Useful High-Entropy Source on Spinel Oxides for Gas Detection

This study aimed to identify a useful high-entropy source for gas detection by spinel oxides that are composed of five cations in nearly equal molar amounts and free of impurities. The sensor responses of the spinel oxides [1# (CoCrFeMnNi)₃O₄, 2# (CoCrFeMnZn)₃O₄, 3# (CoCrFeNiZn)₃O₄, 4# (CoCrMnNiZn)₃O₄, 5# (CoFeMnNiZn)₃O₄, and 6# (CrFeMnNiZn)₃O₄] were evaluated for the test gases (7 ppm NO₂, 5000 ppm H₂, 3 ppm NH₃, and 3 ppm H₂S). In response to NO₂, 1# and 2# showed p-type behavior while 3-6# showed n-type semiconductor behavior. There are three p-type and one n-type AO structural compositions in AB₂O₄[AO·B₂O₃] type spinel, and 1# showed a stable AO composition because cation migration from site B to site A is unlikely. Therefore, it was assumed that 1# exhibited p-type behavior. The p-type behavior of 2# was influenced by Cr oxide ions that were present at the B site and the stable p-type behavior of zinc oxide at the A site. The spinel oxides 3# to 6# exhibited n-type behavior with the other cationic oxides rather than the dominant p-type behavior exhibited by the Zn oxide ions that are stable at the A site. In contrast, the sensor response to the reducing gases H₂, NH₃, and H₂S showed p-type semiconductor behavior, with a particularly selective response to H₂S. The sensor responses of the five-element spinel oxides in this study tended to be higher than that of the two-element Ni ferrites and three-element Ni-Zn ferrites reported previously. Additionally, the susceptibility to sulfurization was evaluated using the thermodynamic equilibrium theory for the AO and B₂O₃ compositions. The oxides of Cr, Fe, and Mn ions in the B₂O₃ composition did not respond to H₂S because they were not sulfurized. The increase in the sensor response due to sulfurization was attributed to the decrease in the depletion layer owing to electron sensitization, as the top surface of the p-type semiconductors, ZnO and NiO, transformed to n-type semiconductors, ZnS and NiS, respectively. High-entropy oxides prepared using the hydrothermal method with an equimolar combination of five cations from six elements (Cr, Mn, Fe, Co, Ni, and Zn) can be used as a guideline for the design of high-sensitivity spinel-type composite oxide gas sensors.

Reduction of hexavalent chromium and degradation of tetracycline using a novel indium-doped Mn2O3 nanorod photocatalyst

This study investigates the photocatalytic reduction of hexavalent chromium (Cr(VI)) and degradation of tetracycline (TC) via visible-light-active In-doped Mn₂O₃ photocatalysis. Mn₂O₃ photocatalysts loaded with different In doses are prepared using a simple hydrothermal method, and the results indicate the formation of Mn₂O₃ nanorod-like structures with good crystallinity. The most significant photocatalytic parameters, namely the catalyst and substrate concentrations, pH, and co-existing ions for the Cr(VI) reduction and TC degradation reactions are systematically examined. Result demonstrates that the Cr(VI) reduction and TC mineralization efficiencies of 52% and 40%, respectively are achieved at the optimum pH of 7, undoped Mn₂O₃ (10 mg/L), and Cr(VI) or TC concentration of 50 mg/L. However, these efficiencies are remarkably increased to 95% and 93%, respectively, when 10 mg/L of 5% In-doped Mn₂O₃ is used as the photocatalyst under the same reaction conditions. Moreover, the co-existing HCO₃^- anions and Ca²⁺ and Mg²⁺ divalent cations considerably deteriorate the performance of the In-doped photocatalysts compared with the SO₄^2- and Cl^- anions and Na⁺ and K⁺ monovalent cations. Liquid chromatography-mass spectrometry analysis reveals that the photodegradation of TC is mainly driven by the elimination of the -CH₃ group followed by the subsequent cleavage of the primary -NHCH₃ group.

Synthesis of 3D Hexagram-Like Cobalt-Manganese Sulfides Nanosheets Grown on Nickel Foam: A Bifunctional Electrocatalyst for Overall Water Splitting

The exploration of low-cost and efficient bifunctional electrocatalysts for oxygen evolution reaction and hydrogen evolution reaction through tuning the chemical composition is strongly required for sustainable resources. Herein, we developed a bimetallic cobalt-manganese sulfide supported on Ni foam (CMS/Ni) via a solvothermal method. It has discovered that after combining with the pure Co₉S₈ and MnS, the morphologies of CMS/Ni have modulated. The obtained three-dimensionally hexagram-like CMS/Ni nanosheets have a significant increase in electrochemical active surface area and charge transport ability. More than that, the synergetic effect of Co and Mn has also presented in this composite. Benefiting from these, the CMS/Ni electrode shows great performance toward hydrogen evolution reaction and oxygen evolution reaction in basic medium, comparing favorably to that of the pure Co₉S₈/Ni and MnS/Ni. More importantly, this versatile CMS/Ni can catalyze the water splitting in a two-electrode system at a potential of 1.47 V, and this electrolyzer can be efficiently driven by a 1.50 V commercial dry battery.

Synergistic Effects of a Multifunctional Graphene Based Interlayer on Electrochemical Behavior and Structural Stability

The ability to rationally design and manipulate the interfacial structure in lithium ion batteries (LIBs) is of utmost technological importance for achieving desired performance requirements as it provides synergistic effects to the electrochemical properties and cycling stability of electrode materials. However, despite considerable efforts and progress made in recent years through the interface engineering based on active electrode materials, relatively little attention has been devoted to address the physical aspects of the interface and interfacial layer between the anode materials layer and the current collector. Here, we propose and successfully grow unique graphene directly on a Cu current collector as an ideal interfacial layer using the modified chemical vapor deposition (CVD). The anode with an engineered graphene interlayer exhibits remarkably improved electrochemical performances, such as large reversible specific capacity (921.4 mAh g(-1) at current density of 200 mA g(-1)), excellent Coulombic efficiency (close to approximately 96%), and superior cycling capacity retention and rate properties compared to the bare Cu. These excellent electrochemical features are discussed in terms of multiple beneficial effects of graphene on interfacial stability and adhesion between the anode and the collector, oxidation or corrosion resistance of the graphene grown Cu current collector, and electrical contact conductance during the charge/discharge process.

Co(II)1-xCo(0)x/3Mn(III)2x/3S Nanoparticles Supported on B/N-Codoped Mesoporous Nanocarbon as a Bifunctional Electrocatalyst of Oxygen Reduction/Evolution for High-Performance Zinc-Air Batteries

Rechargeable Zn-air battery is an ideal type of energy storage device due to its high energy and power density, high safety, and economic viability. Its large-scale application rests upon the availability of active, durable, low-cost electrocatalysts for the oxygen reduction reaction (ORR) in the discharge process and oxygen evolution reaction (OER) in the charge process. Herein we developed a novel ORR/OER bifunctional electrocatalyst for rechargeable Zn-air batteries based on the codoping and hybridization strategies. The B/N-codoped mesoporous nanocarbon supported Co(II)1-xCo(0)x/3Mn(III)2x/3S nanoparticles exhibit a superior OER performance compared to that of IrO2 catalyst and comparable Zn-air battery performance to that of the Pt-based battery. The rechargeable Zn-air battery shows high discharge peak power density (over 250 mW cm(-2)) and current density (180 mA cm(-2) at 1 V), specific capacity (∼550 mAh g(-1)), small charge-discharge voltage gap of ∼0.72 V at 20 mA cm(-2) and even higher stability than the Pt-based battery. The advanced performance of the bifunctional catalysts highlights the beneficial role of the simultaneous formation of Mn(III) and Co(0) as well as the dispersed hybridization with the codoped nanocarbon support.