Nanostructured Manganese Oxide Research Articles

Heteronuclear Fe-Mn Cyclopentadienyl Complexes Supported on Boehmite. Thermochemistry and Thermodynamics of their Decomposition

Boehmite samples with compounds of the composition (C5H5)2FeMnX2(μ-CO)n, where X=Cl, Br and n=1.2, precipitated at room temperature from tetrahydrofuran solutions and then heated in an air flow up to 873 K were obtained and characterized using X-ray diffractometry, infrared Fourier spectroscopy, electron magnetic resonance and temperature-programmed desorption methods. It was shown that the thermal decomposition of these compounds applied to the boehmite samples in the range from room temperature to 873 K occurs stepwise and consists of at least two stages. The first stage of thermal decomposition occurs in the range of 453–753 K, and the second – in the range of 813–843 K. The XRD data show that when calcining at 873 K the boehmite samples with the applied compounds of the above composition and containing these compounds less than 10 wt.%, the diffraction patterns show only reflections characteristic of poorly crystallized aluminum oxide. However, the electron paramagnetic resonance (EPR) spectra of these samples clearly show intense signals characteristic of superpara/ferromagnetic particles of iron and manganese oxides, as well as EPR signals from isolated Fe3+ substituting Al3+ ions in the aluminum oxide structure. EPR spectra most of the iron and manganese is stabilized on the surface of poorly crystallized aluminum oxide in the form of nanostructured iron and manganese oxides.

Exploring the electrochemical and electrocatalytic performance of bismuth oxide and bismuth manganese oxide nanostructures for supercapacitor and water splitting

In this research, bismuth oxide (BO) with non-uniform nanorods featuring a monoclinic crystal structure and bismuth manganese oxide (BMO) with irregularly shaped nanosheets exhibiting a cubic crystal structure were synthesized hydrothermally. These materials were designed for applications in supercapacitors and the oxygen evolution reaction (OER). Electrochemical analysis of BO-NF (Nickel Foam) and BMO-NF electrodes in KOH highlights BMO's superior performance for both supercapacitor and water splitting applications. BMO-NF electrode exhibit higher specific capacitance, lower resistance, and exceptional cyclic stability compared to BO-NF electrode. In asymmetric liquid-state supercapacitor devices, BMO-NF electrode outperforms BO-NF electrode, showcasing advanced capabilities. Additionally, for water splitting, BMO-NF electrode demonstrates a lower overpotential, a more favourable Tafel slope, a larger electrochemical active surface area, and greater stability, underscoring its enhanced efficiency and reliability. Overall, this study shows that the BMO is found to be the more promising material for the energy storage and electrocatalytic applications.

Influence of carbon template and ultrasound irradiation on combustion design of nanostructured calcium manganese oxides used in biodiesel production

Biodiesel, derived from renewable biomass, serves as a sustainable alternative to diesel produced from fossil fuels. This study explores the use of nanostructured MgO/Ca2Mn3O8 catalysts for biodiesel production through transesterification. Ca2Mn3O8 was synthesized as a support catalyst via combustion synthesis, employing carbon templates to control pore size. MgO was impregnated as the active phase using ultrasonic irradiation to enhance particle dispersion. Various characterization techniques, including XRD, FESEM, AFM, TEM, EDX, BET-BJH, and TPD-CO2, were utilized to analyse morphology, porosity, basicity, and active phase dispersion. The use of carbon templates increased pore diameters compared to catalysts without templates, while ultrasonic irradiation improved MgO dispersion. The MgO/Ca2Mn3O8 catalyst with a 10 wt% carbon template and ultrasonic irradiation achieved a maximum conversion rate of 95.5%. Its mesoporous structure, resembling a sponge, facilitated triglyceride diffusion. Stability tests indicated a 90% conversion rate after five reuses. The nanostructured MgO/Ca2Mn3O8 catalyst, with its tailored porosity and structure, demonstrated excellent performance in biodiesel production. Systematically adjusting support porosity and active site dispersion provides a viable approach for designing effective heterogeneous catalysts.

Enhancing Thermal Recovery of Heavy Oil by In Situ Combustion: The Role of Micro and Nanostructured Manganese Oxide Catalysts

Enhancing Thermal Recovery of Heavy Oil by In Situ Combustion: The Role of Micro and Nanostructured Manganese Oxide Catalysts

Tailoring crystalline Mn5O8 nanostructures: Kinetic control and stabilization for enhanced electrocatalytic O2 evolution

The stabilization of manganese oxide nanostructures with tunable oxidation states and morphologies is crucial for regulating catalytic properties. In this study, we aim to stabilize the metastable monoclinic Mn5O8 phase and control the morphology of the Mn5O8 nanostructures using a hydrothermal assisted calcination process in the presence of different precipitating agents. Raman experiments confirmed that the interaction of aqueous Mn2+ salts with different precipitating agents such as NaOH, ammonia, and oleylamine, resulted in the formation of Mn5O8. On the other hand, the precipitation of Mn2+ salt using diammonium oxalate monohydrate as a precipitating agent led to complete oxidation forming Mn2O3. Detailed phase and microstructural analyses were conducted using PXRD, XPS, and FESEM. The analyses revealed the formation of the monoclinic Mn5O8 phase with various morphologies, including hexagonal nanoplates, nanorods, and random nanoplates, when using NaOH, ammonia, and oleylamine as precipitating agents. The synthesized Mn5O8 phase was deposited onto an iron sheet as a substrate. Furthermore, we demonstrated the effect of the structure, morphology, and size of the Mn5O8 material on O2 evolution activity. The catalytic performance of irregularly shaped Mn5O8 nanoplates showed significantly lower η10 (270 mV) and η50 (350 mV) compared to Mn5O8 hexagonal nanoplates, Mn5O8 nanorods, and Mn2O3 nanostructure. Additionally, an insight into the catalytic performance was investigated in detail by evaluating electrochemical active sites, impedance spectroscopy, and hydrophilicity/hydrophobicity of the Mn5O8 material.

Enhancing Photo and Electrocatalytic Activity of Graphene Quantum Dots/Manganese Oxide Nanostructures for Visible Light Photocatalytic and Hydrogen Peroxide Sensing Applications

AbstractDesigning and developing high‐efficiency multifunctional catalysts materials is a significant challenge. In this view, we synthesized Graphene Quantum Dots (gQDs)/Gadolinium Manganese Oxide (GMO) nanostructures for photocatalytic dye degradation and hydrogen peroxide sensing. The structural, optical, composition, and morphology properties of the gQDs/GMO nanostructures were analyzed by using various analytical tools. The gQDs/GMO catalyst shows higher degradation efficiency compared to pure catalysts under visible light irradiation which is due to the large surface area, lower band gap, small amount of hydrogen peroxide (H2O2), and synergetic effect of gQDs/GMO. Furthermore, we extensively investigate the nonenzymatic H2O2 sensing and the gQDs/GMO catalytic materials show higher sensing behavior. From our results, the gQDs embedded in gadolinium‐modified manganese oxide (gQDs/GMO) serve as an efficient photocatalyst material for environmental pollutant degradation under visible light irradiation with and the sensitive electrocatalyst for nonenzymatic H2O2 sensing applications.

Synthesis and phase transformation study of nanostructured manganese oxide polymorphs

This paper presents the green synthesis of manganese oxide nanoparticles using olive leaf extract (OLE). The extract functions as both a reducing agent, responsible for converting manganese ions into nanoparticles, and a capping agent, aiding in stabilizing the formed nanoparticles. Our focus lies on investigating the thermal stability, phase transformation, and decomposition temperatures of different manganese oxide phases in powder form as a function of the calcination temperature. Since phase transformation depends on temperatures change at the nanoscale both thermogravimetric and differential scanning calorimetry (TGA, DSC) are used to determine the new phase transformation temperatures of the synthesized nanoparticles. Moreover, the phase structure and the exact stoichiometry are studied using ex-situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning/transmission electron microscopy (SEM/TEM). XRD and XPS analyses reveal the formation of amorphous MnOx at room temperature (prior to calcination), transitioning to crystalline phases (Mn2O3 and Mn3O4) post-calcination. High-resolution TEM and SEM depict the formation of nanoparticles around 15 nm in size, exhibiting different shapes. BET technique calculations give a very high specific surface area, rending these nanoparticles excellent candidates for several applications.

Review on Medical Applications of Manganese Oxide (Mn2+, Mn3+, and Mn4+) Magnetic Nanoparticles

Apart from our imagination, the nanotechnology industry is rapidly growing and promises that the substantial changes that will have significant economic and scientific impacts be applicable to a wide range of areas, such as aerospace engineering, nanoelectronics, environmental remediation, and medical healthcare. In the medical field, magnetic materials play vital roles such as magnetic resonance imaging (MRI), hyperthermia, and magnetic drug delivery. Among them, manganese oxide garnered great interest in biomedical applications due to its different oxidation states (Mn2+, Mn3+, and Mn4+). Manganese oxide nanostructures are widely explored for medical applications due to their availability, diverse morphologies, and tunable magnetic properties. In this review, cogent contributions of manganese oxides in medical applications are summarized. The crystalline structure and oxidation states of Mn oxides are highlighted. The synthesis approaches of Mn-based nanoparticles are outlined. The important medical applications of manganese-based nanoparticles like magnetic hyperthermia, MRI, and drug delivery are summarized. This review is conducted to cover the future impact of MnOx in diagnostic and therapeutic applications.

Probing the Annealing-Induced Phase Evolution of Nanostructured Manganese Oxide Thin Films by X-Ray Diffraction

Probing the Annealing-Induced Phase Evolution of Nanostructured Manganese Oxide Thin Films by X-Ray Diffraction

An insight of photoelectrochemical driven urea oxidation from nickel manganese oxide nanostructures

Nickel manganese spinel oxide finds tremendous application in electronic and electrochemical devices because of its high redox activity and better durability. Here, we have stabilized nickel rich, nickel manganese oxide Ni6MnO8 through chemical route and studied their application in electrochemical urea oxidation. The as-prepared Ni6MnO8 affords a two-fold high performance toward urea oxidation reaction as photoanode with a maximum peak current density of 44.58 mAcm−2 and exhibited low overpotential of 1.39 V at 10 mAcm−2. Smaller Tafel slope value (16 mV/decade) and 12 h chronoamperometry stability show faster rate kinetics and better durability as photoanode electrocatalyst for urea electrocatalysis. The robust photoelectrochemical urea oxidation is due to Ni2+/Ni3+ redox active species. The present work is sunlight-driven and sustainable approach for hydrogen production and remediation for urea-rich wastewater. It is the first time Ni6MnO8 used as promising photoanode for urea electrocatalysis.

Sonochemically synthesized structures of manganese oxide (MO): A cathode material for oxygen reduction reaction in fuel cell applications

Tailored nanostructures of manganese oxide (MO) were synthesized using a single-step sonochemical method with various morphology-directing agents. The tailored nanostructures of MO were utilized as the cathode material to catalyze the oxygen reduction reaction (ORR) occurring within fuel cells. The obtained MO with various structures were characterized via X-ray diffraction (XRD) analysis, and morphological characterizations were carried out via field emission scanning electron microscopy (FESEM). Raman studies were done to assess the various modes of Raman for MO nanostructures. All the nanostructures of MO were used to modify the surface of the glassy carbon electrode (GCE) to enhance its efficacy in catalyzing the ORR. Amongst five different nanostructures and the conventionally used Pt/C catalyst, MO@NH3OH has shown excellent performance with a higher current density of −0.854 mA/cm2 and a shifted overpotential of −0.44 V. Methanol solution with a higher concentration of 0.5 M was used for the tolerance study and it was observed that MO@NH3OH had shown adequate tolerance and remained unsusceptible to methanol passed towards the cathode side. The stability of the nanostructures was assessed over ∼3000 s using chronoamperometry (CA) and it was found that nanostructures exhibited an impressive 97 % retention of current, which is comparable to the Pt/C electrocatalyst. Therefore, the nanostructure of MO with nanowire morphology could be regarded as a promising Pt-free electrocatalyst obtained via a facile one-step process offering remarkable selectivity and stability while maintaining cost-effectiveness.

Catalytic action and bactericidal behavior of samarium/carbon spheres-doped manganese oxide nanostructures and their molecular docking analysis

The co-precipitation technique was adapted to synthesize different concentrations (2 % and 4 %) of samarium (Sm) doped constant equates of carbon spheres (Cs) and manganese oxide (MnO2). The principal objective of this investigation is to demonstrate confirmation that Sm/Cs-doped MnO2 nanostructures (NSs) owned antibacterial and catalytic attributes. Reduction in surface area manifested to agglomeration, NSs faces become inaccessible to initiate a reaction, can be overcome upon doping of Sm. Sm has the potential to increase the activity of metal oxide ascribed to its electron trapping effect. The structural morphologies, optical properties, functional groups, elemental composition, and d-spacing were determined by applying various characterizations. With the incorporation of CS and Sm, UV–vis spectra shifted towards lower wavelength and band gap energy (Eg) was reduced. MnO2 possessed orthorhombic structure, according to the XRD pattern and TEM exhibited long Burr-like morphology of undoped MnO2. SAED image illustrated that MnO2 is polycrystalline. 4 % Sm/CS doped MnO2 revealed the highest degradation (91 %) in a neutral environment. Furthermore, 4 % Sm/Cs doped-MnO2 revealed an inhibitory zone of 2.85 mm against Escherichia coli (E. coli). Additionally, an analysis of molecular docking revealed a binding interface with NRs and the functional domains of certain cellular proteins. Results indicated that Cs-doped MnO2 and Cs/Sm-doped MnO2 NRs are the most potent DNA gyrase and FabB enzyme inhibitors.

Glancing angle deposition of helical manganese oxide nanostructures on the glass substrate and study the optical nonlinearity by Z-scan technique

Helical manganese oxide nanostructures have been deposited on glass substrate by glancing angle deposition along with electron-beam evaporation technique. X-ray diffraction analysis, FESEM images, and FTIR spectroscopy confirmed the successful growth of the nanostructured thin film. The surface morphology and roughness of the deposited helical manganese oxide thin film were considered using the 2-D and 3-D AFM images. The optical constants along axes a, b, and c have been calculated from the effective medium approximation of Bruggeman. The refractive indices were found to be equal for helical manganese oxide nanostructures along a- and b-axes and greater than the refractive index along c-axis at λ < 600 nm; while these results are reversed for wavelengths greater than 600 nm. The same variations were observed for the extinction coefficients. The Z-scan measurements under continuous-wave (CW) laser irradiation at 532 nm showed a positive sign for both the nonlinear absorption coefficient and nonlinear refractive index of nanostructured helical manganese oxide demonstrating the attendance of induced absorption process and self-defocusing phenomena, respectively. We computed a 3rd-order nonlinear optical susceptibility, χ(3), equal to 0.042 esu that suggests the glancing angle deposited helical manganese oxide nanostructures with a strong nonlinear optical response can be a good candidate to develop nanophotonic devices.

Electrochemical Sensors Based on Manganese and Cobalt Oxide Nanostructures for the Detection of Flutamide and its Derivatives in Real Water Samples

AbstractFlutamide (FLU), bicalutamide (BIC), and hydroxyflutamide (OHF), having a low biodegradability, may cause severe health effects on humans as antiandrogens. In this work, we have developed two electrochemical sensors using manganese oxide (MnO) and Cobalt oxide (CoO) nanostructures (NSs) as electrocatalysts. The GCE modified with MnO is referred to as MnO/GCE and the GCE modified by CoO is referred to as CoO/GCE. The electrochemical behaviours of CoO/GCE and MnO/GCE were examined in ferricyanide solution. It was observed through the employment of cyclic voltammetry that MnO/GCE exhibit better electron transfer than CoO/GCE. The calculated surface coverage values, 1.46 x10−9 mol cm−2 and 5.02 x10−9 mol cm−2 of MnO/GCE and CoO/GCE suggest a multilayer of a metal oxide molecule film at the surfaces of glassy carbon electrodes (GCE). FLU, BIC and OHF were detected at a linear range from 32.01 to 50.00 µM. The limits of detection of FLU, BIC and OHF were 18.5, 13.0 and 78.8 µM at MnO/GCE respectively and 18.8, 18.7 and 18.5 µM at CoO/GCE respectively. Both MnO/GCE and CoO/GCE showed good catalytic stability towards detecting FLU and its derivatives. FLU, BIC and OHF were also detected in the presence of interferents for both electrochemical sensors in phosphate buffer solution. Both MnO/GCE and CoO/GCE confirmed good selectivity without cross interference. Some of the health effects associated with FLU, BIC and OHF are liver damage, prostate inflammation, and methamoglobenia. Although FLU, BIC and OHF are detected in low concentration levels in water bodies, their continuous ingestion is a great concern. As far as we know, MnO and CoO NSs have not been used to electrochemically detect FLU, BIC and OHF. Furthermore, OHF has not been detected electrochemically before and there are only a few studies on the electrochemical detection of BIC. Hence, MnO and CoO NSs are used in this study for the first time for an electrochemical sensor fabrication towards the detection of FLU, BIC and OHF.

Facile fabrication of an electrochemical sensor for the determination of two sulfonamide antibiotics in milk, honey and water samples using the effective modification of carbon paste electrode with graphitic carbon nitride and manganese oxide nanostructures

Facile fabrication of an electrochemical sensor for the determination of two sulfonamide antibiotics in milk, honey and water samples using the effective modification of carbon paste electrode with graphitic carbon nitride and manganese oxide nanostructures

Scalable Synthesis of Pre‐Intercalated Manganese(III/IV) Oxide Nanostructures for Supercapacitor Electrodes: Electrochemical Comparison of Birnessite and Cryptomelane Products

AbstractManganese(III/IV) oxide is a promising pseudocapacitive material for supercapacitor electrodes due to favorable attributes such as its chemical resilience, high earth abundance and low specific cost. Herein, the morphological, compositional and electrochemical characteristics of co‐precipitated manganese(III/IV) oxide products, each described by the general formula NaxKyMnOz, are investigated to establish how these properties are influenced by synthesis conditions. NaxKyMnOz growths in low‐temperature (&lt;100 °C) basic and acidic environments are shown to promote the formation of turbostratic birnessite and cryptomelane phases, respectively, with the latter polymorph containing a relatively low concentration of interstitial Na+ and K+ cations. It is demonstrated that K+ pre‐insertion during synthesis yields lower initial charge‐transfer resistances than equivalent Na+ intercalation, and that this parameter correlates strongly with storage performance. Accordingly, Na‐mediated storage initially delivers inferior specific capacitances and Coulombic efficiencies than K‐based mechanisms, but K+ intercalation/deintercalation causes faster capacitance decay during prolonged galvanostatic cycling. Furthermore, whilst crystallographic phase is shown to have a weaker effect on NaxKyMnOz storage properties than the choice of intercalating guest cations, cryptomelane electrodes are more susceptible to cycling‐induced capacitance and efficiency losses than their birnessite counterparts. In combination, these insights provide an instructive foundation for the optimization of NaxKyMnOz in high‐power storage applications.

Electrochemical properties of MnO2-based carbon nanomaterials for energy storage and electrochemical sensing

Electrochemical alongside the electro-catalytic properties of graphene and multi-walled carbon nanotubes have been improved via doping with manganese oxide nanostructures. Structural, morphological, and electrochemical properties of the as-synthesized nanocomposites were identified using XRD, FTIR, SEM, and electrochemical methods including cyclic voltammetry, and electrochemical impedance spectroscopy. The SEM images showed flower-like microsphere structures, while the conjugation of MnO2 with the carbon nanomaterials was confirmed by the FTIR and XRD analysis. All MnO2-based nanocomposites provided great enhancement in their electrochemical activities with a larger value of specific capacitance than the individual constituents of carbon nanomaterials. Accordingly, hydrogen peroxide-directed detection was evaluated, whereas the nanocomposites exhibited direct electron transfer, fast and linear responses in the range from 1.0 to 210 µM. Thus, the significant enhancements in the electrochemical features acquired by the nanocomposites could suggest these nanomaterials for energy storage and hydrogen peroxide sensing applications.

Nanostructured manganese oxide on fullerene soot for water oxidation under neutral conditions

The sluggish kinetics of oxygen-evolution reaction (OER) through water-oxidation reaction results in high overpotentials for water splitting. Among different compounds, carbon-based material/Mn oxide composites were reported as OER catalysts. Fullerene soot (FS), which contains a mixture of fullerenes and carbon blacks, is low-cost compared to fullerenes and is commercially available. Herein, the Mn oxide/fullerene soot (MnOx/FS) composite was investigated as an OER catalyst under neutral conditions. The composite was prepared through the reaction of KMnO4 and FS as a facile, easy, and low-cost procedure. In this method, amorphous Mn oxide is formed directly on FS. The material was characterized by a number of methods. Then, the OER catalytic activity of MnOx/FS was studied in a LiClO4 solution (pH ≈ 6.3). Compared to pristine FS, the OER activity of MnOx/FS is 2.5 times higher at 2.25 V vs. RHE. The Tafel slopes for OER are 450 and 240 mV per decade for FS and the reported composite, respectively.

A manganese dioxide-silver nanostructure-based SERS nanoplatform for ultrasensitive tricyclazole detection in rice samples: effects of semiconductor morphology on charge transfer efficiency and SERS analytical performance.

Taking advantage of metal-semiconductor junctions, functional nanocomposites have been designed and developed as active substrates for surface-enhanced Raman scattering (SERS) sensing systems. In this work, we prepared three types of nanocomposites based on manganese oxide (MnO2) nanostructures and electrochemically synthesized silver nanoparticles (e-AgNPs), which differed according to the morphologies of MnO2. The SERS performance of MnO2 nanosheet/e-Ag (MnO2-s/e-Ag), MnO2 nanorod/e-Ag (MnO2-r/e-Ag), and MnO2 nanowire/e-Ag (MnO2-w/e-Ag) was then evaluated using tricyclazole (TCZ), a commonly used pesticide, as an analyte. Compared to the others, MnO2-s/e-Ag exhibited the most remarkable SERS enhancement. Thanks to its large surface area and ability to accept/donate the electrons of the semiconductor, MnO2-s acted as a bridge to improve the charge transfer efficiency from e-Ag to TCZ. In addition, the MnO2 content of the nanocomposites was also considered to optimize the SERS sensing performance. With the optimal MnO2 content of 25 wt%, MnO2-s/e-Ag could achieve the best SERS performance, allowing the detection of TCZ at concentrations down to 6 × 10-12 M in standard solutions and 10-11 M in real rice samples.

Nanostructured manganese oxide on carbon for water oxidation: New findings and challenges

Water-oxidation reaction (WOR) is a sluggish reaction for hydrogen production through water splitting. Herein, Mn oxide/mesoporous carbon (MC) is introduced as an active WOR catalyst under neutral conditions. The composite was synthesized through the reaction of permanganate and MC using a simple and low-cost procedure and characterized by scanning electron microscopy, in situ visible spectroscopy, energy-dispersive spectroscopy, (high-resolution) transmission electron microscopy, and X-ray diffraction. Then, the WOR activity of this composite was investigated under neutral conditions. The experiment shows that nanosized Mn oxide/MC is a promising catalyst for water-splitting systems. The overpotentials for the onset (based on the Tafel plot) and 1.0 mA of WOR are 700 and 940 mV, respectively. Based on the LSV, the Tafel slope is 378.6 mV per decade.