Manganese Oxide Deposits Research Articles

Manganese potential of Neogene rocks in Central Russia (Tambov-Lipetsk region)

Materials related to the manganese potential of Neogene rocks (Sosnovka Formation) in Central Russia are summarized. Concretions and geoides in primary manganese carbonates are most likely early diagenetic formations. However, we cannot also rule out the possibility of their formation after the early diagenetic (catagenetic) stage of sediment transformation. The Tambov-Lipetsk region with manganese potential outlined in this paper is located in an economically favorable setting. Probability of the discovery of commercial manganese oxide deposits in this region is discussed.

Electrodeposition of Nanoscale Manganese Oxide for Electrochemical Energy Storage Devices

As society moves away from fossil fuels towards renewable energy sources, energy storage is becoming increasingly important. Manganese oxide is a good candidate material for multiple energy storage applications (e.g., rechargeable batteries and supercapacitors) because it is environmentally benign and has good catalytic and electrochemical properties. When used as a supercapacitor, manganese oxide stores charge through electric double layer and redox effects. To maximize these effects, the structure of manganese oxide deposits needs to be optimized; this means increasing the effective surface area of the deposit. In addition to the effective surface area, the crystal structure of the deposit also greatly affects both catalytic and electrochemical performance. Manganese oxide is polymorphic and it is important to understand the crystallography of the manganese oxide within a device, in order to optimize its properties. In this work, nickel foam is coated with high surface area manganese oxide through a simple anodic electrodeposition procedure. Nickel foam is an excellent substrate for many energy storage devices because in addition to nickel’s good conductivity, the porosity of the foam increases surface area and also facilitates fluid flow through the substrate. The latter is important for applications where manganese oxide is being used as a catalyst. The electrolyte used for deposition of manganese oxide contains manganese acetate, ammonium acetate and dimethyl sulfoxide. By varying deposition and post deposition annealing conditions, different microstructures are obtained. The microstructure, crystallography and chemical state of the manganese oxide deposits are characterized through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS analysis has been used to determine that manganese oxide is in the form of MnO2. Preliminary XRD and TEM results indicate that the deposits obtained in this work are nanocrystalline with grains less than 20 nm in size. Electrochemical tests such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are used to determine performance (e.g., capacitance and cyclability) and to optimize the morphology and structure of the manganese oxide deposits. Preliminary CV measurements suggest that the manganese oxide deposits on nickel foam exhibit good areal and specific capacitance.

Redox deposition of birnessite-type manganese oxide on silicon carbide microspheres for use as supercapacitor electrodes.

Silicon carbide microsphere/birnessite-type MnOx (SiC/B-MnOx) composites were prepared by removal of a SiO2 layer with redox deposition of birnessite-type MnOx for supercapacitor electrode materials. The characterization studies showed that the birnessite-type MnOx in the composite was homogeneously deposited on the SiC surface. The capacitive properties of the as-prepared SiC/B-MnOx electrodes were measured in a three-electrode system using 1 M Na2SO4(aq) as the electrolyte. The SiC/B-MnOx(6) electrode, fabricated using a MnOx/SiC feeding ratio of 6:1, displayed a specific capacitance of 251.3 F g(-1) at 10 mV s(-1). Such excellent electrochemical performance is attributed to an increase in the electrical conductivity in the presence of silicon carbide, an increase in the effective interfacial area between MnOx and the electrolyte, and the contact area between MnOx and silicon carbide. The deposition of birnessite-type MnOx on a SiC surface may be a prospective fabrication technique for electrode materials for supercapacitors.

Nucleation and Growth Mechanisms of an Electrodeposited Manganese Oxide Oxygen Evolution Catalyst

We investigate the mechanisms of nucleation and steady-state growth of a manganese oxide catalyst (MnOx) electrodeposited from Mn2+ solutions in a weakly basic electrolyte. Early catalyst growth was probed through chronoamperometry transients, which were fit to reveal a progressive nucleation mechanism for initial catalyst formation. Time-dependent atomic force microscopy snapshots of the electrode surface reveal a rapid increase in nucleus size together with a sluggish rise in coverage, which is also characteristic of progressive nucleation. Electrochemical kinetic studies of the catalyst growth yield a Tafel slope of approximately 2.3 × RT/2F and a rate law consisting of a second-order and inverse fourth-order dependence on [Mn2+] and proton activity, respectively. These results are consistent with a deposition mechanism involving rate-limiting disproportionation of aqueous Mn3+, resolving a longstanding ambiguity surrounding the deposition of manganese oxides under nonacidic conditions.

Potentiostatic and cyclic voltammetric deposition of nanostructured manganese oxide for supercapacitor applications

Nanostructured manganese oxide was produced by potentiostatic and cyclic voltammetric deposition techniques from aqueous KMnO4 solutions. Scanning electron microscopy (SEM) and X-ray diffraction were used to study the morphology and crystal structure of the deposited films. The electrochemical properties of deposited films, that obtained by two techniques, were investigated via performing the cyclic voltammetric tests. The results showed the higher specific capacitances of the nanostructured manganese oxide electrodes which have been produced via cyclic voltammetric deposition. The good retention was obtained for all synthesized electrode materials.

Biogenic Manganese–Calcium Oxides on the Cell Walls of the Algae Chara Corallina: Elemental Composition, Atomic Structure, and Water‐Oxidation Catalysis

AbstractChara corallina freshwater algae produce brown deposits of manganese oxides on their cell wall surfaces when growing in manganese‐rich media. We report on the formation, topology, composition, atomic structure, and catalytic activities of these biogenic manganese oxides (BMOs). The deposits are volcano shaped and exhibit 3–5 μm craters in their centers. Microfocus X‐ray irradiation and detection of characteristic X‐ray fluorescence lines allowed elemental mapping at 5 μm spatial resolution and the identification of the volcano‐shaped deposits as a Mn–Ca oxide. X‐ray absorption spectroscopy (XAS) revealed a high‐valent MnIII/IV oxide. The structural analysis involved XAS spectra collected for a single volcano at room temperature and for single cells at 20 K. On the basis of the XAS data, the oxides were identified as members of the birnessite family of layered manganese oxides containing di‐μ‐oxido‐bridged MnIII/IVO6 octahedra as central building units. The deposits share structural motifs with synthetic water‐oxidizing Mn–Ca oxides and with the Mn4Ca complex of photosystem II, the biological water‐oxidation catalyst. Model reactions demonstrate low, but clearly detectable, activity of the manganese deposits for water‐oxidation catalysis. The biogenic manganese oxides on the cell walls of Chara corallina thus represent an intriguing object to study how manganese‐based catalysts for water oxidation are formed in a biological environment. The formation of BMOs in relation to cellular ion transport and the possibility of BMOs to fulfill a detoxification function in plants were also examined.

A Mechanistic Investigation on the Anodic Deposition of Layered Manganese Oxide

A kinetic and mechanistic investigation has been carried out on the anodic deposition of layered manganese oxide from aqueous MnSO4 solutions containing chloride salts of potassium, tetraethylammonium (TEA), and cetyltrimethylammonium (CTA) cations. Linear sweep voltammetry and the resulting Tafel plots revealed that electron transfer rate increases with the presence of CTA and with increasing its concentration, which can be ascribed to a decrease in activation energy for the oxidation of Mn2+. Chronoammperometry under diffusion-controlled conditions demonstrated that the steady state current is dependent in magnitude on the type of coexisting cations. The slope of the Cottrell plot decreased with an increase in the size of cations examined, indicating that the reaction is limited by the rate of mass transfer of coexisting cations toward negative charges on the just-deposited Mn oxide. The film grown under the control of diffusion of coexisting cations showed well-crystallized birnessite phase, while that deposited at lower overpotential was X-ray amorphous or low crystalline. Especially, the film grown with CTA was highly crystallized, which can be explained in terms of the low crystalline growth rate at the steady state, as well as its self-assembling property arising from hydrophobic interaction.

Electrodeposited Nano-flakes of Manganese Oxide on Macroporous Ni Electrode Exhibiting High Pseudocapacitance

A porous nickel (P-Ni) substrate was prepared by selective leaching of zinc from pressed pellets containing powders of Ni & Zn in 4 M NaOH solution. Anodic deposition of manganese oxide onto the porous Ni substrate (/P-Ni) formed nano-flakes of manganese oxide layers as revealed in SEM studies. Pseudocapacitance of this oxide electrode was evaluated by cyclic voltammetry (CV) and chronopotentiometry (CHP) in 2 M NaOH solution. The specific capacitance of the Mn oxide electrode was as high as 1515 F , which was ten times higher than Mn oxide deposited on a flat Ni-ribbon. 80% of capacity was retained after 200 charge/discharge cycles. The system showed no loss of activity in dry form over period of days. The impedance studies indicated highly conducting /P-Ni substance and the obtained specific capacitance from impedance data showed good agreement with the charge/discharge measurements.

Uncovering the origin of the black stains in Lascaux Cave in France

Lascaux Cave in France was discovered in 1940. Since being opened to visitors the cave has suffered three major microbial outbreaks. The current problem is the fast dissemination of black stains which are threatening the Palaeolithic paintings. Previous data pointed to the involvement of new fungal species in the formation of black stains on the rock walls and ceiling. However, it appears that there could be other reasons for the formation of different and extensive black stains coating the surface of the clayey sediments. Our analyses reveal that black stains on clayey sediments are mainly produced by Acremonium nepalense, a manganese oxide-depositing fungus, widely distributed in the cave. Thus, in Lascaux Cave, the black stains have a dual origin: on limestone rocks they are mainly produced by the accumulation of fungal melanins, and on clayey sediments by the biogenic deposition of black manganese oxides.

Electrochemical deposition of nanostructured manganese oxide on hierarchically porous graphene–carbon nanotube structure for ultrahigh-performance electrochemical capacitors

A 3D graphene sheet–carbon nanotube (GS–CNT) structure with a good wetting property, high porosity, and large surface area is homogeneously deposited with active amorphous manganese oxide (a-MnOx) by potentiodynamic deposition. The flowery a-MnOx nanostructure with ultra-slender petals (ca. 5–8 nm) on the framework of hierarchically porous GS–CNT matrix not only enables nearly full utilization of a-MnOx but also retains sufficient conductivity and porosity for the high-rate charge–discharge application. The use of a-MnOx on the 3D GS–CNT material produces a specific capacitance of MnOx of 1200 F g−1 which is much-higher than that of a pure a-MnOx electrode (CS,Mn = 233 F g−1). The specific energy and specific power of a-MnOx/GS–CNT are respectively as high as 46.2 Wh kg−1 and 33.2 kW kg−1, revealing that our work conceptually provides a way to produce porous structures composed of graphene, carbon nanotubes, and various electroactive materials for high-performance energy storage devices.

Electrophoretic deposition of MnO2-coated carbon nanotubes on a graphite sheet as a flexible electrode for supercapacitors

A flexible electrode was prepared by microwave heating deposition of manganese oxide (MnO2) on carbon nanotubes (CNTs) followed by electrophoretic deposition of the MnO2-coated CNTs on a flexible graphite sheet (FGS). The prepared MnO2-coated CNTs were characterized by scanning and transmission electron microscopy, and X-ray diffraction. A uniformly thin nano-scale MnO2 coating was formed on the surface of the CNTs. The MnO2-coated CNTs–FGS electrode showed highly capacitive behaviour in the 0.5M Na2SO4 aqueous solution, with a specific capacitance of 442.9F/g based on MnO2 at 2mV/s. It exhibited an excellent cycling stability with no more than 1.1% capacitance loss after 1000cycles at 50mV/s.

Asymmetric deposition of manganese oxide in single walled carbon nanotube films as electrodes for flexible high frequency response electrochemical capacitors

Manganese oxide (MnO2) is a promising pseudocapacitive electrode material because of its high capacitance, abundant resource, low-cost, and environmental friendliness. However, its poor electrical and ionic conductivities and low stability hinder applications. Forming MnO2 nanocomposites with high surface area porous metal, carbon materials, or conducting polymers is a possible solution. In this work, we have developed a facile and scalable asymmetric in situ deposition method to incorporate MnO2 nanoparticles in conductive single walled carbon nanotube (SWCNT) films. The high porosity of vacuum filtrated SWCNT films accommodates pseudocapacitive MnO2 nanoparticles without sacrificing the mechanical flexibility and electrochemical stability of SWCNT films. We exposed one side of SWCNT films to acidic potassium permanganate (KMnO4) solution. The infiltrated KMnO4 solution partially etches SWCNTs to create abundant mesopores, which ensure electrolyte ions efficiently access deposited MnO2. Meanwhile, the remaining SWCNT network serves as excellent current collectors. The electrochemical performance of the SWCNT–MnO2 composite electrodes depends on the porosity of SWCNT films, pH, and concentration of KMnO4 solution, deposition temperature and time. Our optimized two-electrode electrochemical capacitor, with 1M Na2SO4 in water as electrolyte, showed a superior performance with specific capacitance of 529.8Fg−1, energy density of 73.6Whkg−1, power density of 14.6kWkg−1, excellent capacitance retention (99.9%) after 2000 charge and discharge cycles, and one of the highest reported frequency responses (knee frequency at 1318Hz). The high performance flexible electrochemical capacitors have broad applications in portable electronics and electrical vehicles, especially when high frequency response is desired.

Les grottes d'Azé (Saône-et-Loire, France) : de la roche altérée aux sédiments

The Azé cave (south Burgundy), from alteration to ghost-rock. The goal of this study was to gain a better understanding of the formation of the Azé Caves and the relationships which exist at this site between the surrounding rock and the sediments. A detailed study of the limestones from the Late Aalenian to the Early Bathonian which make up the surrounding rock shows that they contain considerable quantities of quartz and hundreds of ppm of manganese. Certain levels contain numerous siliceous cherts. From the Jurassic, the region underwent several phases of immersion. This period was also marked by a tectonic phase of weak amplitude. The faulting which occurred at this time allowed the circulation of meteoric water through the limestone leading to the dissolving of calcium carbonates and to phases of dolomitisation and dédolomitisation. As a result, "ghost rock" was created in the different stratigraphie units. However the hydrodynamism of these flows was weak and the alteration of the rock was isovolumic without evacuation of the alterite. During the Oligocene, the Méconnais region underwent a more severe tectonic phase. The structure of leaning blocks that we see today was put in place and the "ghost rock" was fractured by larger faults. As a result a hydrodynamic potential was created between the different sides of the massifs and the alterite was removed by water thus creating the caves. From that time on bacterial activity was able to develop on the walls of the cavities and in the residual alterite. The bacteria oxidised the manganese and iron contained in the limestone leading to the accumulation of manganese and iron oxide deposits in the limestone and on the walls, often in the form of structured encrustings. These bacteria were still active during certain periods of the Quaternary as shown by the discovery of deposits on bear bones. Under the effect of gravity, the least soluble limestone residues and the conglomerations of manganese formed by bacteria fell to the bottom of the caves or were carried away by flowing water. Depending on the hydrodynamic regime, these residues (clays, sands, gravels, pebbles) were to varying extents transported by water and were removed from or left behind in the caves. As a result, the sandy fractions of sediments deposited at the time of flows with the weakest hydrodynamism are mostly made up of these residues.

Composite films prepared by immersion deposition of manganese oxide in carbon nanotubes grown on graphite for supercapacitors

Manganese oxide/carbon nanotube (CNT) composite films on graphite were prepared by growing CNTs on the substrate using chemical vapor deposition (CVD), followed by immersion in an aqueous solution of potassium permanganate. The CVD growth created favorable conditions for deposition of the oxide on the electrode, and an aligned porous structure of the composite films, which originated from the CNT growth, could be managed. Electrochemical behaviors of the CNT and the composite films for supercapacitors were studied in 1 M Na2SO4 solution. While the oxide deposition in the CNT films was identified as contributing to capacitance enhancement, it was also found that a mild heat treatment could improve performance of the composite films.

Development of carbon-supported hybrid catalyst for clean removal of formaldehyde indoors

A novel hybrid catalyst for a clean removal of formaldehyde indoors with a long lifetime was developed via a deposition of manganese oxide (MnOx) catalysts on a polyacrylonitril-based activated carbon nanofiber (PAN-ACNF) support. The combination of MnOx with PAN-ACNF induced synergic effects on the formaldehyde removal performance; twofold performance improvements were obtained as compared with PAN-ACNF alone not only in dry condition but also in the extremely humid condition at room temperature without an irradiation of the UV light. The two-staged removal process, the adsorption of formaldehyde in the PAN-ACNF micropores followed by the oxidative decomposition by the deposited MnOx nanoparticles, was found to afford the superior formaldehyde removal performance of the developed hybrid catalyst, MnOx@PAN-ACNF.

Two-, Three-, and Four-Component Magnetic Multilayer Onion Nanoparticles Based on Iron Oxides and Manganese Oxides

Magnetic multilayered, onion-like, heterostructured nanoparticles are interesting model systems for studying magnetic exchange coupling phenomena. In this work, we synthesized heterostructured magnetic nanoparticles composed of two, three, or four components using iron oxide seeds for the subsequent deposition of manganese oxide. The MnO layer was allowed either to passivate fully in air to form an outer layer of Mn(3)O(4) or to oxidize partially to form MnO|Mn(3)O(4) double layers. Through control of the degree of passivation of the seeds, particles with up to four different magnetic layers can be obtained (i.e., FeO|Fe(3)O(4)|MnO|Mn(3)O(4)). Magnetic characterization of the samples confirmed the presence of the different magnetic layers.

Manganese Oxide/Carbon Aerogel Composite: an Outstanding Supercapacitor Electrode Material

AbstractManganese oxide/carbon aerogel composite electrodes are prepared by a self‐limiting anodic‐electrochemical deposition of manganese oxide into a binder‐enriched carbon aerogel layer, drop‐cast on a graphite substrate, using 0.1 M Mn(CH3COO)2·4H2O as the electrolyte. Manganese oxide grows in the form of thin nanofibers along the backbone of the carbon aerogel, leaving adequate working space for the electrolyte and enabling a fuller extent of the utilization of the manganese oxide to make the composite an outstanding supercapacitor electrode material. The manganese oxide is determined to be Mn3O4 with the Raman spectroscopy and high‐resolution transmission electron microscopy. The rectangularity of the cyclic‐voltammogram loops of the composite electrode is excellent and remains that way for scan rates up to a very‐high value of 500 mV s−1, indicating extremely good redox reversibility and cycle efficiency. At a scan rate of 25 mV s−1, the specific capacitance, as measured in 0.5 M Na2SO4 for a potential window of 0.1–0.9 V vs. Ag/AgCl, reaches a maximum value of 503 F g−1 and experiences only a negligible decay of less than 1% at the 6000th cycle, implying an extraordinary cycling stability. The cycling efficiency is as high as 98% at a current density of 8 A g−1 cm−2, showing an almost‐ideal capacitive behavior. The power density reaches 48.5 kW kg−1 and the energy density 21.6 W h kg−1 at a scan rate of 500 mV s−1, well above the specifications of current state‐of‐the‐art supercapacitors.

MnO2/TiN heterogeneous nanostructure design for electrochemical energy storage

MnO(2)/TiN nanotubes are fabricated using facile deposition techniques to maximize the surface area of the electroactive material for use in electrochemical capacitors. Atomic layer deposition is used to deposit conformal nanotubes within an anodic aluminium oxide template. After template removal, the inner and outer surfaces of the TiN nanotubes are exposed for electrochemical deposition of manganese oxide. Electron microscopy shows that the MnO(2) is deposited on both the inside and outside of TiN nanotubes, forming the MnO(2)/TiN nanotubes. Cyclic voltammetry and galvanostatic charge-discharge curves are used to characterize the electrochemical properties of the MnO(2)/TiN nanotubes. Due to the close proximity of MnO(2) with the highly conductive TiN as well as the overall high surface area, the nanotubes show very high specific capacitance (662 F g(-1) reported at 45 A g(-1)) as a supercapacitor electrode material. The highly conductive and mechanically stable TiN greatly enhances the flow of electrons to the MnO(2) material, while the high aspect ratio nanostructure of TiN creates a large surface area for short diffusion paths for cations thus improving high power. Combining the favourable structural, electrical and energy properties of MnO(2) and TiN into one system allows for a promising electrode material for supercapacitors.

Framework Doping of Cobalt into Layered Manganese Oxide for Improved Capacitive Behavior

Anodic deposition of layered manganese oxides has been carried out at various bath temperatures in the presence of cobalt ions. Crystallinity of the layered Mn oxide increased with increasing the bath temperature. In the deposition of the layered Mn oxide, Co2+ ions were not involved at room temperature, while at 70°C the presence of Co2+ exhibited a catalytic current suggesting the formation of Mn and Co composite. Addition of Co2+ did not provide any new diffraction peaks but caused broadening of the peaks due to Mn oxide. This indicates the introduction of Co ions into the Mn oxide sheets. Doping of Co into the Mn oxide framework caused a drastic increase in the specific capacitance.

Immobilization of Cationic Porphyrin between Multilayers of Manganese Oxide during Their Electrochemical Assembly

Potentiostatic electrolysis of a mixed aqueous solution of MnSO4 and cationic porphyrin at +1.0 V (vs Ag/AgCl) on a Pt electrode resulted in the deposition of layered manganese oxide. Porphyrin molecules are intercalated between Mn oxide layers as a cation form, resulting in a stacking with a repeating periodicity of 0.82 nm.