Papers by Keyword: Manganese Dioxide

Abstract: The present study explores the green conflation of manganese dioxide (MnO₂) nanoparticles through a simple, Eco-friendly, and cost-effective system. This conflation process involves the response of potassium permanganate with an waterless splint excerpt of Hibiscus rosa- sinensis, serving as both a reducing and stabilizing agent. The green conflation system is profitable as it avoids poisonous chemicals, making it safer for both the terrain and implicit operations. The synthesized MnO₂ nanoparticles were considerably characterized using colorful logical ways. X-ray diffraction (XRD) analysis was used to confirm the liquid structure, while Fourier- transfigure infrared (FT- IR) spectroscopy handed sapience into the functional groups present in the material. UV-Visible spectroscopy was employed to study the optic parcels and band gap of the synthesized nanoparticles. Morphological details were observed through Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), which revealed the nanoparticles in globular shape and nanoscale size. One of the notable findings of this study is the photocatalytic effectiveness of the synthesized MnO₂ nanoparticles. Under visible light irradiation, these nanoparticles effectively degraded methyl orange color in waterless results, showcasing their eventuality as an effective photocatalyst. also, the synthesized MnO₂ nanoparticles demonstrated promising operations in the junking of organic adulterants from water, emphasizing their environmental significance. Overall, this study contributes to the development of sustainable nanomaterials for environmental remediation, particularly for wastewater treatment operations. The green conflation approach, combined with the excellent catalytic parcels of MnO₂ nanoparticles, underscores the material's eventuality for practical and large- scale operations.

Abstract: Through a simple electrodeposition technique, SnO₂/MnO₂ nanocomposite films were directly deposited onto ultrathin stainless-steel (SS) foils for use in electrochemical supercapacitors. The materials were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Electrochemical experiment revealed that the SnO₂/MnO₂ electrodes exhibited a high gravimetric capacitance of 876 F/g at a current density of 1 A/g. Furthermore, an asymmetric supercapacitor was fabricated using the SnO₂/MnO₂ nanocomposite as the positive electrode and activated carbon as the negative electrode. This asymmetric device demonstrated a capacitance of 72.2 F/g at 1 A/g and retained approximately 87.5% of its initial capacitance after 28,000 cycles, highlighting its excellent cycling stability and practical application potential. The combination of high capacitance and robust stability makes this SnO₂/MnO₂ nanocomposite a promising candidate for high-performance supercapacitor electrodes.

Abstract: Production of nanoscale catalytic materials is an urgent technological challenge. Catalysts have a wide range of applications, such as for neutralizing nuclear waste, decontaminating water polluted with mercury, purifying the atmosphere from various micro-particles, in molecular sieves, and in chemical synthesis, oil refining, etc. Another important application of nanostructured materials is in rechargeable batteries and fuel cells, where their high specific surface area is essential to ensure the speed and effectiveness of the interactions between different materials. Active nanostructured materials with a sufficiently high density of controlled surface defects meet these requirements well and, therefore, offer significant potential for optimizing the high energy consumption in batteries. Currently, the particle size of natural and industrially synthesized manganese oxide materials is typically in the micron range or larger. From perspectives, the most developed and promising methods for synthesizing manganese dioxide are ion exchange, hydrothermal, electrolytic, and chemical synthesis. In this work, a distinctive method for synthesizing nanostructured manganese dioxide is proposed, described, and analyzed. Experiments were conducted to determine the optimal synthesis routes using the Self-propagating High-temperature Synthesis (SHS) method, as a distinctive technological approach that uses manganese ore enrichment waste as raw material and ammonium chloride as a pretreatment chemical agent.

Abstract: Metal oxide nanoparticles are widely used in various fields, including catalysis, sensing, energy storage, and more. Manganese dioxide (MnO₂) is a promising material for gas sensors due to its sensitivity to various gases, including oxidizing and reducing gases. The calcination temperature affects their size, crystallinity, surface area, and other properties. In the present research work, the influence of calcination temperature on the structural, electrical and gas sensing properties of MnO₂ nanoparticles or nanopowders was investigated. The MnO₂ nanopowder was calcinated at 200, 400, 600, and 800 °C in a muffle furnace for 4 hours. After that, using the calcinated powder of MnO₂, the thick films were prepared using the standard screen printing technique. The structural characterizations were investigated using SEM, EDS, and XRD. It has been found that as the calcination temperature is increased, the electrical, structural, and gas-sensing properties of MnO₂ change. The prepared thick films calcinated at 200, 400, 600, and 800 °C are labeled as samples 1, 2, 3, and 4, respectively, in this paper. It has been found that sample 4 shows maximum resistivity, a more specific surface area, a smaller crystallite, and a maximum gas response to H₂S gas. The maximum sensitivity was found to be 76.32% to H₂S gas at operating temperature 120 °C. The response and recovery time was also found quickly.

Abstract: A composite of manganese dioxide nanosheet and graphene (MnO₂/graphene) has been prepared by co-exfoliation of the manganese dioxide with flower-like nanostructure and graphite in isopropanol. The composite has been characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results of TEM, XPS, and SEM evidenced that the MnO₂/graphene composite with nanosheet structure has been prepared successfully. This composite is further cast on glassy carbon electrode to make up a sensor to detect hydrogen peroxide (H₂O₂). The range of linear detection for H₂O₂ is 0.5-237 μM. The detection limit of the sensor is 0.07 μM (S/N=3).

Abstract: Manganese dioxide (MnO₂) is a promising electrode material for electrochemical supercapacitor applications due to its low cost, eco-friendly and high theoretical specific capacitance in a wide potential window. In this study, MnO₂ and Ag-doped MnO₂ are prepared by cathodic electrodeposition on graphite substrate from electrolyte with the main compound of potassium permanganate using pulse potentiostatic technique. The effect of Ag doping on the morphology, structure and electrochemical properties of MnO₂ materials are investigated. Scanning electron microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), cyclic voltammetry (CV), galvanostatic charge-discharge measurement and electrochemical impedance spectroscopy (EIS) are used for characterization of the prepared materials. The results show that doping Ag into the MnO₂ structure has improved electrochemical characteristics of materials. The specific capacitances are calculated for pure MnO₂ and Ag-doped MnO₂ to be 272.84 and 277.48 F/g, respectively. The prepared materials exhibit the high charge-discharge stability, maintaining at about 92 % for MnO₂ and 95 % for Ag-doped MnO₂ after 500 cycles of the charge-discharge operation.

Abstract: The structural properties and capacitive behavior of manganese dioxide (MnO₂) films prepared by potentiostatic cathodic deposition were examined in presence and absence of pre-electrophoretically deposited reduced graphene oxide (rGO) film. The FTIR analysis reflects the formation of a MnO₂/rGO composite film structure. SEM and TEM characterization show that the MnO₂ film deposited on rGO film has finer and less compact nanostructure and grown as sparsely aggregated particles follow the open structure of underlying rGO platelets. The specific capacitance and rate capability of MnO₂/rGO film are higher than that of pristine MnO₂ film; it exhibits specific capacitance of 292 Fg^-1 at 1 mA cm^-2 and better cyclic stability at 3 mA cm^-2. The presence of 3D underlying defective rGO film creates an open structure with larger area, facilitates the electron transfer and access of the electrolyte ions through the surface of MnO₂ film and hence offering the potential of the unique capacitive behavior.

Abstract: To enhance the formaldehyde decomposition performance of original MnO₂ powder, the polyacrylonitrile nanofibers loaded with MnO₂ nano/microparticles (denoted as MnO₂/PAN) was prepared via a facile method, which combined the low-temperature liquid phase deposition and electrospinning. With the assistance of electrospinning, MnO₂ nano/microparticles can distribute uniformly on both outside and inside of PAN nanofibers. Such a hybrid nanostructure would effectively enhance the specific surface area, thence facilitating the catalytic decomposition of formaldehyde. As a result, the MnO₂/PAN nanofibers manifest a high-efficiency catalytic capacity of formaldehyde decomposition, with around 44.0% formaldehyde removal rate after 12h (60 °C, pH = 2). In addition, it also shows a better reusability than pure MnO₂ powder.

Abstract: The impact of Li⁺ dopant-ions in fluorine-containing electrolytes on electrodeposited manganese (IV) oxide material was under investigation in this paper. The dependence of phase composition of this material at Li⁺-concentration range in the electrolyte below the stoichiometric content of lithium in hollandite A₂Mn₈O₁₆ (Mn:Li ≈ 4:1) was established. The hollandite phase stabilization as a template effect caused by Li⁺-ions is gradually reduced with the Li⁺ concentration growth from 0.025 to 0.15mol∙L^-1 LiOH concentration range. The hollandite content sharply drops at close to the stoichiometric Mn:Li ratio for the hollandite phase. In contrary, the concentration of cation-deficient ε-MnO₂ becomes significant. Thus, the template effect of Li⁺ cations at electrolytic doping from fluorine-containing electrolytes consists of stabilization of the hollandite tunnels at longer distance with the size of coherent scattering regions of this phase more than of about 20—50 Å comparing with undoped materials. It is supposed that Li⁺-ions presence makes tunnel space unavailable unlike water molecules or ammonium cations. Therefore, to realise molecular sieves based on manganese (IV) oxides the availability of tunnels should be taken into account.

Abstract: Lithium air batteries have aroused a considerable concern all over the world owing to their outstanding performances. Especially, catalysts of the air electrode, as one of the most core components of lithium air batteries, have been most extensively studied in recent years. In this paper the nanometer manganese dioxide catalysts and their compounds with Super P, TNRGO and OMC were prepared successfully via hydrothermal synthetic method. Characterized by XRD, SEM and BET, most of them have regular shape, perfect dispersion and high specific surface area, especially S_BET of MnO₂/TNRGO/OMC of the three-component catalysts was up to 126.70m²/g. The air electrodes with nanoMn0₂/carbons catalysts have lower resistance, and better reversibility.