Highly Active Manganese Oxide from Electrolytic Manganese Anode Slime for Efficient Removal of Antibiotics Induced by Dissociation of Peroxymonosulfate

In this paper, high-activity manganese oxide was prepared from electrolytic manganese anode slime to realize the efficient removal of antibiotics. The effects of sulfuric acid concentration, ethanol dosage, liquid-solid ratio, leaching temperature and leaching time on the leaching of manganese from electrolytic manganese anode slime were systematically studied. Under the optimal conditions, the leaching rate of manganese reached 88.74%. In addition, a Mn₃O₄ catalyst was synthesized and used to activate hydrogen persulfate (PMS) to degrade tetracycline hydrochloride (TCH). The synthesized Mn₃O₄ was characterized by XRD, XPS, Raman, SEM and HRTEM. As a result, the prepared Mn₃O₄ is spherical, with high purity and crystallinity. The catalytic activity of Mn₃O₄ for PMS to degrade TCH was increased to 82.11%. In addition, after four cycles, the performance remained at 78.5%, showing excellent stability and recyclability. In addition, O₂^- and ¹O₂ are the main active species in the degradation reaction. The activity of Mn₃O₄ is attributed to it containing Mn(II) and Mn(III) at the same time, which can quickly realize the transformation of high-valence and low-valence manganese, promote the transfer of electrons and realize the degradation of organic pollutants.

Constructing new Fe3O4@MnOx with 3D hollow structure for efficient recovery of uranium from simulated seawater

Enrichment of uranium from seawater is a promising method for addressing the energy crisis. Current technologies are generally not effective for enriching uranium from seawater because its concentration in seawater is low. In this study, new Fe₃O₄@MnO_x with 3D hollow structure, which is capable of enriching low concentration uranium, was prepared via a novel redox etching method. The physicochemical characteristics of Fe₃O₄@MnO_x were studied with TEM, HRTEM, SEAD, FTIR, XRD, and N₂ adsorption-desorption analysis. Dynamic kinetic studies of different initial U(VI) concentrations revealed that the pseudo-second-order model fit the sorption process better, and the sorption rates of Fe₃O₄@MnO_x in 1, 10, and 25 mg/L U(VI) solution were 0.0124, 0.00298, and 0.000867 g/mg·min, respectively. Isothermal studies showed that the maximum sorption amounts were 50.09, 56.27, and 64.62 mg/g for 1, 10, and 25 mg/L U(VI), respectively, at pH 5.0 and 313 K, suggesting that Fe₃O₄@MnO_x could effectively enrich low concentration U(VI) from water. The sorption amount of U(VI) did not significantly decrease in the presence of Na⁺, Mg²⁺, and Ca²⁺. HRTEM, FTIR, and XPS results demonstrated that Fe(II) and Mn/Fe-O-H active sites in Fe₃O₄@MnO_x were accounted for the high and specific enrichment efficiency. A column experiment was conducted to evaluate the U(VI) sorption efficiency of Fe₃O₄@MnO_x in simulated seawater. The U(VI) sorption efficiency remained above 80% in 28 days run. Our findings demonstrate that Fe₃O₄@MnO_x has extraordinary potential for the enrichment of uranium from simulated seawater.

Augmenting the electrochemical performance of NiMn2O4 by doping of transition metal ions and compositing with rGO

The transition metal ions (TMIs) such as Co²⁺ and Zn²⁺ doped NiMn₂O₄ (NMO)/rGO nanocomposite synthesized by facile sol-gel method was used for the fabrication of supercapacitor. The presence of metal ions in the nanocomposite was confirmed by X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscope (HR-TEM) mapping techniques. The fabricated electrode showed high specific capacitance of 710 F/g which was 3-fold higher than NMO (254 F/g). The addition of RGO in the nanocomposite increased the cycle stability of TMIs doped NMO significantly from 51 to 91%. In addition, the symmetric supercapacitor (SSC) fabricated using TMIs doped NMO/rGO nanocomposite with 3.5 M KOH as an electrolyte delivered a maximum energy density of 43 Wh/kg and power density of 10 kW/kg. Furthermore, the SSC device retained 90% of capacitance retention over 10,000 cycles with coulombic efficiency of 99% at 5 A/g. These result suggested that the TMIs doped NMO/rGO nanocomposite electrode is a promising material for high-energy supercapacitors.

Switching the solubility of electroactive ionic liquids for designing high energy supercapacitor and low potential biosensor

Ionic liquids are regarded as one of the most prodigious materials for sustainable technological developments with superior performance and versatility. Hence, in this study, we have reported the design and synthesis of electroactive disubstituted ferrocenyl ionic liquids (Fc-ILs) with two different counter anions and demonstrated the significance of their anion tuneable physicochemical characteristics towards multifunctional electrochemical applications. The Fc-IL synthesized with chloride counter anion (Fc-Cl-IL) displays water-solubility and can be used as a redox additive in the fabrication of supercapacitor. Supercapacitor device with Fc-Cl-IL based redox electrolyte exhibits outstanding energy and power densities of 91 Wh kg^-1 and 20.3 kW kg^-1, respectively. Meanwhile, ferrocenyl IL synthesized with perchlorate anion (Fc-ClO₄-IL) exhibits water-insolubility and can serve as a redox mediator towards construction of a glucose biosensor. The biosensor comprising Fc-ClO₄-IL is able to detect glucose at an exceptionally lower potential of 0.2 V, with remarkable sensitivity and selectivity. This study implies that the introduction of electroactive ILs could afford supercapacitor devices with high energy and power densities and biosensors with less detection potential.

Ultra-stable Mn1-xNixCO3 nano/sub-microspheres positive electrodes for high-performance solid-state asymmetric supercapacitors

Long-term cycling performance of electrodes for application in supercapcitor has received large research interest in recent years. Ultra-stable Mn1-xNixCO3 (x-0, 0.20, 0.25 and 0.30) nano/sub-microspheres were synthesized via simple co-precipitation method and the Mn1-xNixCO3 was confirmed by XRD, FT-IR, XPS and their morphology was studied by SEM and TEM analysis. Among the various Mn1-xNixCO3 electrodes, the Mn0.75Ni0.25CO3 electrode exhibited the higher specific capacitance (364 F g-1 at 1 A g-1) with capacity retention of 96% after 7500 cycles at 5 A g-1. Moreover, the assembled solid-state asymmetric supercapacitor based on Mn0.75Ni0.25CO3//graphene nanosheets performed a high specific capacity of 46 F g-1 and energy density of 25 Wh kg-1 at a power density of 499 W kg-1 along with high capacity retention of 87.7% after 7500 cycles. The improved electrochemical performances are mainly owing to the intrinsic conductivity and electrochemical activity of MnCO3 after Mn1-xNixCO3 (x-0.20, 0.25 and 0.30) with appropriate Ni concentration. This study highlights the potentiality of the Mn0.75Ni0.25CO3//GNS asymmetric supercapacitor device for promising energy storage applications.

Study on the Synthesis of Mn3o4 Nanooctahedrons and Their Performance for Lithium Ion Batteries

Among the transition metal oxides, the Mn₃O₄ nanostructure possesses high theoretical specific capacity and lower operating voltage. However, the low electrical conductivity of Mn₃O₄ decreases its specific capacity and restricts its application in the energy conversion and energy storage. In this work, well-shaped, octahedron-like Mn₃O₄ nanocrystals were prepared by one-step hydrothermal reduction method. Field emission scanning electron microscope, energy dispersive spectrometer, X-ray diffractometer, X-ray photoelectron spectrometer, high resolution transmission electron microscopy, and Fourier transformation infrared spectrometer were applied to characterize the morphology, the structure, and the composition of formed product. The growth mechanism of Mn₃O₄ nano-octahedron was studied. Cyclic voltammograms, galvanostatic charge-discharge, electrochemical impedance spectroscopy, and rate performance were used to study the electrochemical properties of obtained samples. The experimental results indicate that the component of initial reactants can influence the morphology and composition of the formed manganese oxide. At the current density of 1.0 A g^-1, the discharge specific capacity of as-prepared Mn₃O₄ nano-octahedrons maintains at about 450 mAh g^-1 after 300 cycles. This work proves that the formed Mn₃O₄ nano-octahedrons possess an excellent reversibility and display promising electrochemical properties for the preparation of lithium-ion batteries.

The oxygen reduction reaction of two electron transfer of nitrogen-doped carbon in the electro-Fenton system

Degradation mechanism of ORR for the NGO-Ti mesh cathode material in the EF process.

Environmental friendly synthesis of TiO2-ZnO nanocomposite catalyst and silver nanomaterilas for the enhanced production of biodiesel from Ulva lactuca seaweed and potential antimicrobial properties against the microbial pathogens

TiO₂-ZnO heterogeneous catalytic system provides a good replacement of a homogeneous catalytic reaction due to its easier recovery. In this study, biodiesel was produced from Ulva lactuca seaweeds using TiO₂-ZnO nanocomposite catalysts with particle size of ~12 nm. The size controlled TiO₂-ZnO nanocomposite was characterized by powder XRD analysis and TEM. The result of that TiO₂-ZnO catalyst is a promising catalyst for the production of biodiesel under mild reaction conditions and high yield of hydroxydecanoic acid conversion of 82.8%. The various conditions optimized for the higher conversion to FAME (15.8 ml of FAME) were 4 wt% catalysts at 4 h under 60 °C and further there is no increase of conversion to FAME above 60 °C-80 °C. The total product yield was calculated as 82.8% of conversion to FAME. The evaluated biodiesel was found to be up to the mark of ASTM standards. The silver nanoparticles (AgNPs) were synthesized by using leftover biomass of algae obtaining after lipid extraction of U.lactuca. AgNPs particle size was achieved as ~12 nm and was confirmed by UV-Visible spectroscopy, XRD and TEM analysis. Antibacterial activities of the synthesized AgNPs were analyzed and compared. The antibacterial activity was excellent against bacterial pathogens and treatment against P. vulgaris shows the maximum zone of inhibition (13.8 mm). The present work identified that the unutilized bioresource such as U.lactuca can be effectively utilized for biodiesel production so as to replace fossil fuel usage.

Fabrication of 9.6 V High-performance Asymmetric Supercapacitors Stack Based on Nickel Hexacyanoferrate-derived Ni(OH)2 Nanosheets and Bio-derived Activated Carbon

Hydrated Ni(OH)₂ and activated carbon based electrodes are widely used in electrochemical applications. Here we report the fabrication of symmetric supercapacitors using Ni(OH)₂ nanosheets and activated carbon as positive and negative electrodes in aqueous electrolyte, respectively. The asymmetric supercapacitors stack connected in series exhibited a stable device voltage of 9.6 V and delivered a stored high energy and power of 30 mWh and 1632 mW, respectively. The fabricated device shows an excellent electrochemical stability and high retention of 81% initial capacitance after 100,000 charge-discharges cycling at high charging current of 500 mA. The positive electrode material Ni(OH)₂ nanosheets was prepared through chemical decomposition of nickel hexacyanoferrate complex. The XRD pattern revealed the high crystalline nature of Ni(OH)₂ with an average crystallite size of ~10 nm. The nitrogen adsorption-desorption isotherms of Ni(OH)₂ nanosheets indicate the formation of mesoporous Ni(OH)₂ nanosheets. The chemical synthesis of Ni(OH)₂ results the formation of hierarchical nanosheets that are randomly oriented which was confirmed by FE-SEM and HR-TEM analysis. The negative electrode, activated porous carbon (OPAA-700) was obtained from orange peel waste. The electrochemical properties of Ni(OH)₂ nanosheets and OPAA-700 were studied and exhibit a high specific capacity of 1126 C/g and high specific capacitance of 311 F/g at current density of 2 A/g, respectively. Ni(OH)₂ nanosheets delivered a good rate performance and remarkable capacitance retention of 96% at high current density of 32 A/g.

Realizing an Asymmetric Supercapacitor Employing Carbon Nanotubes Anchored to Mn3O4 Cathode and Fe3O4 Anode

A facile route to anchor pseudocapacitive materials on multiwalled carbon nanotubes (CNTs) to realize high-performance electrode materials for asymmetric supercapacitors (ASCs) is reported. The anchoring process is developed after direct decomposition of metal-hexacyanoferrate complex on the CNT surface. Transmission electron microscopy (TEM) analysis reveals that the nanoparticles (NPs) are discretely attached over the CNT surface without forming a uniform layer, thus making most of the entire NP surface available for electrochemical reactions. Accordingly, CNT-Mn₃O₄ nanocomposite cathode shows significantly improved capacitive performance as compared to pristine CNT electrode, validating the efficacy of designing the composite electrode. With CNT-Fe₃O₄ nanocomposite as the paired anode, the hybrid ASC delivers a specific capacitance of 135.2 F/g at a scan rate of 10 mV/s within a potential window of 0-1.8 V in the aqueous electrolyte and retains almost 100% of its initial capacitance after 15,000 cycles. The serially connected ASCs can power commercial light-emitting diodes (LEDs) and mobile phones, reflecting their potential in next-generation storage applications.

Electrochemical, top-down nanostructured pseudocapacitive electrodes for enhanced specific capacitance and cycling efficiency

Stabilization of the electroactive redox centers on ideally polarisable conductive electrodes is a critical challenge for realizing stable, high performing pseudocapacitive energy storage devices. Here, we report a top-down, electrochemical nanostructuring route based on voltammetric cycling to stabilize β-MnO₂ on a single walled carbon nanotube (CNT) scaffold from a MnMoO₄ precursor. Such in situ nanostructuring results in controlled disintegration of an ∼8 μm almond like structure to form ∼29 nm β-MnO₂ resulting in a 59% increase in the specific surface area and a 31% increase in the porosity of the pseudocapacitive electrode. Consequently, the specific capacitance and areal capacitance increase by ∼75% and ∼40%, respectively. Such controlled, top-down nanostructuring is confirmed through binding energy changes to Mo 3d, C 1s, O 1s and Mn 2p respectively in XPS. Furthermore, Raman spectral mapping confirms the sequential nanostructuring initiating from the interface of CNTs with MnMoO₄ and proceeding outwards. Thus, the process yields the final CNT/β-MnO₂ electrode that is electrically conductive, facilitates rapid charge transfer, and has increased capacitance and longer stability. Furthermore, the charge-transfer resistance and equivalent resistance are significantly lower compared to conventional activated carbon based electrodes.

A novel electrocatalytic nanocomposite of reduced graphene oxide/silver nanocube hybrid decorated imprinted polymer for ultra-trace sensing of temozolomide

A new nanocomposite of reduced graphene oxide/silver nanocube hybrid decorated molecularly imprinted polymer at the surface of a screen-printed carbon electrode was developed for the electroanalysis of an anticancerous drug, temozolomide, at the ultra-trace level.

Mesoporous manganese phthalocyanine-based materials for electrochemical water oxidation via tailored templating

Electrochemical water splitting using non-noble metals as catalysts is of increasing importance for the future energy sector.

Facile synthesis of Mesoporouscobalt Hexacyanoferrate Nanocubes for High-Performance Supercapacitors

Mesoporous cobalt hexacyanoferrate nanocubes (meso–CoHCF) were prepared for the first time through a facile sacrificial template method. The CoHCF mesostructures possess a high specific surface area of 548.5 m²·g⁻¹ and a large amount of mesopores, which enable fast mass transport of electrolyte and abundant energy storage sites. When evaluated as supercapacitor materials, the meso–CoHCF materials exhibit a high specific capacitance of 285 F·g⁻¹, good rate capability and long cycle life with capacitance retention of 92.9% after 3000 cycles in Na₂SO₄ aqueous electrolyte. The excellent electrochemical properties demonstrate the rational preparation of mesoporous prussian blue and its analogues for energy storage applications.

All-solid-state asymmetric supercapacitors based on cobalt hexacyanoferrate-derived CoS and activated carbon

All-solid-state flexible asymmetric supercapacitors fabricated using CoS and AC showed a high cell voltage, high specific capacitance, and high energy density of 5.3 W h kg⁻¹ with excellent electrochemical stability.

Aloe vera Derived Activated High-Surface-Area Carbon for Flexible and High-Energy Supercapacitors

Materials which possess high specific capacitance in device configuration with low cost are essential for viable application in supercapacitors. Herein, a flexible high-energy supercapacitor device was fabricated using porous activated high-surface-area carbon derived from aloe leaf (Aloe vera) as a precursor. The A. vera derived activated carbon showed mesoporous nature with high specific surface area of ∼1890 m²/g. A high specific capacitance of 410 and 306 F/g was achieved in three-electrode and symmetric two-electrode system configurations in aqueous electrolyte, respectively. The fabricated all-solid-state device showed a high specific capacitance of 244 F/g with an energy density of 8.6 Wh/kg. In an ionic liquid electrolyte, the fabricated device showed a high specific capacitance of 126 F/g and a wide potential window up to 3 V, which results in a high energy density of 40 Wh/kg. Furthermore, it was observed that the activation temperature has significant role in the electrochemical performance, as the activated sample at 700 °C showed best activity than the samples activated at 600 and 800 °C. The electron microscopic images (FE-SEM and HR-TEM) confirmed the formation of pores by the chemical activation. A fabricated supercapacitor device in ionic liquid with 3 V could power up a red LED for 30 min upon charging for 20s. Also, it is shown that the operation voltage and capacitance of flexible all-solid-state symmetric supercapacitors fabricated using aloe-derived activated carbon could be easily tuned by series and parallel combinations. The performance of fabricated supercapacitor devices using A. vera derived activated carbon in all-solid-state and ionic liquid indicates their viable applications in flexible devices and energy storage.

A "copolymer-co-morphology" conception for shape-controlled synthesis of Prussian blue analogues and as-derived spinel oxides

The morphologically and compositionally controlled synthesis of coordination polymers and spinel oxides is highly desirable for realizing new advanced nanomaterial functionalities. Here we develop a novel and scalable strategy, containing a "copolymer-co-morphology" conception, to shape-controlled synthesis of various types of Prussian blue analogues (PBAs). Three series of PBAs MyFe1-y[Co(CN)6]0.67·nH2O (MyFe1-y-Co, M = Co, Mn and Zn) with well-controlled morphology have been successfully prepared through this strategy. Using MnyFe1-y-Co PBAs as the model, by increasing the relative content of Mn, flexible modulation of the morphology could be easily realized. In addition, a series of porous MnxFe1.8-xCo1.2O4 nano-dices with well-inherited morphologies and defined cation distribution could be obtained through a simple thermal treatment of the PBAs. All these results demonstrate the good universality of this novel strategy. When evaluated as an electrocatalyst, the octahedral-site Mn(III)/Mn(IV) content in MnxFe1.8-xCo1.2O4, mainly determined by sensitive (57)Fe Mössbauer in combination with X-ray photoelectron spectroscopic techniques, was discovered to be directly correlated with the oxygen reduction/evolution reaction (ORR/OER) activity.

Facile and scalable route to sheets-on-sheet mesoporous Ni–Co-hydroxide/reduced graphene oxide nanocomposites and their electrochemical and magnetic properties

Sheets-on-sheet mesoporous Ni–Co-hydroxide/RGO nanocomposite with a specific capacitance of 835 F g⁻¹ was obtained by the chemical decomposition of nickel cobalt hexacyanoferrate complex.

Oxygen evolution catalytic behaviour of Ni doped Mn3O4 in alkaline medium

In this study, the electrocatalytic behavior of Mn₃O₄ was enhanced by non-precious metal doping.

Photochemical fabrication of 3D hierarchical Mn3O4/H-TiO2 composite films with excellent electrochemical capacitance performance

We report a novel photodeposition strategy for the fabrication of 3D hierarchical Mn₃O₄/H-TiO₂ composite films with prominent pseudocapacitive performance.