Manganese Carbonate Research Articles

Layer-by-layer hollow photosensitizer microcapsule design via a manganese carbonate hard template for photodynamic therapy in cells

Microcapsules fabricated using layer-by-layer self-assembly have unique properties, making them attractive for drug delivery applications. The technique has been improved, allowing the deposition of multiple layers of oppositely charged polyelectrolytes on spherical, colloidal templates. These templates can be decomposed by coating multiple layers, resulting in hollow shells. In this paper, we describe a novel drug delivery system for loading photosensitizer drugs into hollow multilayered microcapsules for photoprocess applications. Manganese carbonate particles were prepared by mixing NH4HCO3 and MnSO4 and performing consecutive polyelectrolyte adsorption processes onto these templates using poly-(sodium 4-styrene sulfonate) and poly-(allylamine hydrocholoride). A photosensitizer was also incorporated into the layers. Hollow spheres were fabricated by removing the cores in the acidic solution. The hollow, multilayered microcapsules were studied by scanning electron microscopy, steady-state, and time-resolved techniques. Their biological activity was evaluated in vitro with cancer cells using a conventional MTT assay. The synthesized CaCO3 microparticles were uniform, non-aggregated, and highly porous spheres. The phthalocyanine derivatives loaded in the microcapsules maintained their photophysical behaviour after encapsulation. The spectroscopic results presented here showed excellent photophysical behaviour of the studied drug. We observed a desirable increase in singlet oxygen production, which is favourable for the PDT protocol. Cell viability after treatment was determined and the proposed microcapsules caused 80% cell death compared to the control. The results demonstrate that photosensitizer adsorption into the CaCO3 microparticle voids together with the layer-by-layer assembly of biopolymers provide a method for the fabrication of biocompatible microcapsules for use as biomaterials.

Paleoproterozoic manganese and base metals deposits at Kisenge-Kamata (Katanga, D.R. Congo)

The Kisenge-Kamata manganese deposit (Katanga, D.R. Congo) belongs to a group of Paleoproterozoic sedimentary manganese ore occurrences that have been recognized for various parts of Africa. It is a relatively small deposit with total estimated reserves of ∼12 Mt ore, but it is of major importance for understanding key aspects of the geology of the Kasai Block of the Congo Craton. The available constraints indicate that the deposit formed in the 2.0–1.9 Ga time interval, in the Orosirian period. The manganese-rich facies of the Kisenge-Kamata deposits range in composition from manganese carbonate rocks to non-calcareous deposits dominated by manganese-rich garnet. Associated rocks are mainly grey graphitic shales. The Kisenge-Kamata sediments are significantly enriched in Cu, Co, Ni, Zn and other accessory metals (V, Mo, Ga). Field constraints and geochemical data suggest that the Kisenge-Kamata sediments were probably deposited in a relatively small intracratonic basin (graben) within the Kasai Block, with an inlet allowing periodical access for ocean water influx carrying Mn, REE and other metals. Primary carbonate ore has relatively low δ13C (−3 to −6‰) and high δ18O (+13 to +20‰) values, confirming their derivation from marine fluids.

Ag2O nanoparticles/MnCO3, –MnO2 or –Mn2O3/highly reduced graphene oxide composites as an efficient and recyclable oxidation catalyst

Silver oxide nanoparticles doped manganese (IV) oxide along with varying percentages of highly reduced graphene oxide (HRG) [Ag2O(1%)–MnO2/(X%)HRG] nanocomposites were fabricated through a simple co-precipitation method followed by calcination at 400 °C. The as-prepared nanocomposite upon calcination at 300 °C and 500 °C temperatures, yields the manganese carbonate (MnCO3) and manganese (III) oxide (Mn2O3) composites i.e. Ag2O(1%)–MnCO3/(X%)HRG and Ag2O(1%)–Mn2O3/(X%)HRG, correspondingly. The structural composition of the prepared nanocomposites has confirmed by several characterization techniques. The nanocomposites have successfully utilized as a catalyst for liquid-phase oxidation of aromatic alcohols in presence of O2 as a green oxidant under alkali-free conditions. In addition, a comparative study was performed to assess the activity of the manganese carbonates and manganese oxides for aerial oxidation of benzyl alcohol into benzaldehyde as a model reaction. Effects of various parameters have thoroughly examined in detail and the Ag2O(1%)–MnO2/(5%)HRG catalyst exhibited the highest activity in the aerial oxidation of benzyl alcohol to benzaldehyde with a 100% conversion and >99% selectivity in a remarkably short reaction time (35 min) than the undoped precursor i.e. Ag2O(1%)–MnO2. The presence of HRG dopant greatly enhanced the catalytic performance of Ag2O–MnO2 nanocatalysts could be attributed to the presence of carbon vacancies and topological defects as well as oxygen carrying functionalities on the HRG surface and increase in the surface area. The as-prepared catalyst could be efficiently recycled and reused up to five times without a discernible drop in its catalytic performance and the product selectivity remained unchanged. The prepared catalyst i.e. Ag2O(1%)–MnO2/(5%)HRG was employed as oxidation catalyst for a series of various substituted benzylic and aliphatic alcohols into their respective aldehydes and yielded complete conversion with excellent product selectivity with no further oxidation to acids.

Anodic Lodes and Scrapings as a Source of Electrolytic Manganese

Manganese is an element of interest in metallurgy, especially in ironmaking and steel making, but also in copper and aluminum industries. The depletion of manganese high grade sources and the environmental awareness have led to search for new manganese sources, such as wastes/by-products of other metallurgies. In this way, we propose the recovery of manganese from anodic lodes and scrapings of the zinc electrolysis process because of their high Mn content (>30%). The proposed process is based on a mixed leaching: a lixiviation-neutralization at low temperature (50 °C, reached due to the exothermic reactions involved in the process) and a lixiviation with sulfuric acid at high temperature (150–200 °C, in heated reactor). The obtained solution after the combined process is mainly composed by manganese sulphate. This solution is then neutralized with CaO (or manganese carbonate) as a first purification stage, removing H2SO4 and those impurities that are easily removable by controlling pH. Then, the purification of nobler elements than manganese is performed by their precipitation as sulphides. The purified solution is sent to electrolysis where electrolytic manganese is obtained (99.9% Mn). The versatility of the proposed process allows for obtaining electrolytic manganese, oxide of manganese (IV), oxide of manganese (II), or manganese sulphate.

An ultra-high surface area mesoporous carbon prepared by a novel MnO-templated method for highly effective adsorption of methylene blue

Mesoporous carbon is considered as the most effective adsorbent for dyes with large molecule diameter. In this study, an ultra-high surface area mesoporous carbon was derived using a kind of new template precursors (manganese salts), i.e. manganese carbonate (MC), manganese oxalate (MO) and manganese acetate (MA). The XRD results demonstrated that after the pyrolysis of the mixture of manganese salts and poly(vinyl alcohol) (PVA) over 500 °C, MnO was only the Mn species on carbon and the particle sizes of the generated MnO were in the range of 1.92–15.11 nm, with the lowest value derived from MO. All prepared carbons presented evident mesoporous characteristics, with higher specific surface areas (SBET) at 2138 m2/g, mesopore volume (Vmeso) at 3.56 cm3/g, and mesopore ratios > 95%, together with the lowest and narrowest mesopore size distribution, for the MO-templated sample. The sample had high adsorption capacities for methylene blue, up to 1791 mg/g, and extremely fast adsorption rates with the adsorption equilibrium time within 1 min, which was significantly higher than previous studies. The results demonstrated that the novel MnO-templated method is very promising for the preparation of high surface area mesoporous carbon for highly effective adsorption of methylene blue.

Polycrystalline and Mesoporous 3-D Bi2O3 Nanostructured Negatrodes for High-Energy and Power-Asymmetric Supercapacitors: Superfast Room-Temperature Direct Wet Chemical Growth.

Superfast (≤10 min) room-temperature (300 K) chemical synthesis of three-dimensional (3-D) polycrystalline and mesoporous bismuth(III) oxide (Bi2O3) nanostructured negatrode (as an abbreviation of negative electrode) materials, viz., coconut shell, marigold, honey nest cross section and rose with different surface areas, charge transfer resistances, and electrochemical performances essential for energy storage, harvesting, and even catalysis devices, are directly grown onto Ni foam without and with poly(ethylene glycol), ethylene glycol, and ammonium fluoride surfactants, respectively. Smaller diffusion lengths, caused by the involvement of irregular crevices, allow electrolyte ions to infiltrate deeply, increasing the utility of inner active sites for the following electrochemical performance. A marigold 3-D Bi2O3 electrode of 58 m2·g-1 surface area has demonstrated a specific capacitance of 447 F·g-1 at 2 A·g-1 and chemical stability of 85% even after 5000 redox cycles at 10 A·g-1 in a 6 M KOH electrolyte solution, which were higher than those of other morphology negatrode materials. An asymmetric supercapacitor (AS) device assembled with marigold Bi2O3 negatrode and manganese(II) carbonate quantum dots/nickel hydrogen-manganese(II)-carbonate (MnCO3QDs/NiH-Mn-CO3) positrode corroborates as high as 51 Wh·kg-1 energy at 1500 W·kg-1 power and nearly 81% cycling stability even after 5000 cycles. The obtained results were comparable or superior to the values reported previously for other Bi2O3 morphologies. This AS assembly glowed a red-light-emitting diode for 20 min, demonstrating the scientific and industrial credentials of the developed superfast Bi2O3 nanostructured negatrodes in assembling various energy storage devices.

A Low-Cost and Easily Prepared Manganese Carbonate as an Efficient Catalyst for Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran

A low-cost and easily prepared manganese carbonate (MnCO3) has been synthesized for catalytic conversion of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF). The properties and morphology of the manganese carbonate were measured by SEM, XRD, TGA, BET and XPS. In this method, no harsh reaction conditions were required, and it was a simple and green process for the oxidation of 5-HMF into DFF. To achieve an optimum DFF yield, different reaction conditions, including reaction temperature, reaction time, catalyst amount, and solvents were investigated. Results from the experiments indicated that the highest DFF yield of 86.9% was obtained at 120 °C under atmospheric oxygen pressure after 6 h. Finally, MnCO3 could be used at least five times with considerable stability.

Bifunctional electrocatalytic CoNi-doped manganese oxide produced from microdumbbell manganese carbonate towards oxygen reduction and oxygen evolution reactions

Manganese carbonate microdumbbells grown via an oriented attachment mechanism were employed as a template for producing a bifunctional Co/Ni-doped MnO2 electrocatalyst towards the ORR/OER.

High temperature transesterification of soybean oil with methanol using manganese carbonate as catalyst

The manganese carbonate catalyst, prepared by precipitation method, was used in transesterification of soybean oil under subcritical condition of methanol. Catalyst samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The triacylglycerol (TAG) conversion and fatty acid methyl esters (FAME) yield were determined using high performance liquid chromatography (HPLC). The transesterification was realized for 1 h using various working conditions: 0-3 wt.% of catalyst (based on the mass of oil), the mole ratio of methanol to oil from 13:1 to 27:1 and temperature ranging from 393 to 473 K. A maximum TAG conversion of 98.1% could be obtained at the optimal reaction conditions: 2 wt.% of catalyst, methanol/oil mole ratio of 21:1, for 1 h in a batch reactor at 453 K. Kinetic analysis showed that the model based on mass transfer and chemical reaction at the catalyst surface confirmed the experimental data. Using that kinetic expression, the effect of continuous transesterification was proposed and verified by a 360-h long realized experiment in a laboratory packed-bed reactor (PBR). Slow deactivation of the catalyst was caused by leaching of Mn in both biodiesel and glycerol phases and by blocking the active sites of the catalyst with organic compounds.

MnF2-Ni and MnCO3-Ni derived from the same raw materials for high-performance supercapacitor

Manganese fluoride and manganese carbonate grown on nickel foam were successfully synthesized via a hydrothermal method using the same raw materials and their electrochemical performances were compared. Manganese fluoride grown on nickel foam gained with double NH4F at 80 °C displays a specific capacitance of 411.25 F g−1 at 200 mA g−1 and retains 65.85% of the initial capacitance (164 F g−1) at 2 A g−1 after 5000 cycles. While manganese carbonate grown on nickel foam obtained with regular NH4F at 160 °C exhibits a higher specific capacitance of 533 F g−1 at 200 mA g−1 and that of 228 F g−1 at 2 A g−1 with a capacitance retention of 59.65% after 5000 cycles.

Selective precipitation of Cu in manganese-copper chloride leaching liquor

Recovery of valuable metal from industrial waste is critically important for wastewater treatment and recycling. In the present work, we developed a new method for selective copper extraction from the actual industrial manganese-copper chloride leaching liquor, which was produced in wet extraction of cobalt. The theoretical pH value for selective copper precipitation was calculated, which was in the range of 2.80–4.71. Manganese carbonate was used for selective copper deposition, and the factors that could affect the precipitation performance were investigated. The procedure for selective precipitation of copper was optimized as follows: the amount of manganese carbonate was twice the theoretical amount of neutralization acid; the reaction temperature and time were 60°C and 4.0h, respectively. Under the optimal conditions, the copper deposition rate was higher than 90%, while the deposition rates of other ions were lower than 10%. The XRD and SEM results showed that the copper-rich precipitate was granular and its main component was Cu2(OH)3Cl.

Mixed Zinc/Manganese on Highly Reduced Graphene Oxide: A Highly Active Nanocomposite Catalyst for Aerial Oxidation of Benzylic Alcohols

Nanocomposites of highly reduced graphene oxide (HRG) and ZnOx nanoparticles doped manganese carbonate containing different percentages of HRG were prepared via a facile co-precipitation method. The prepared sample calcined at 300 °C yielded i.e., ZnOx(1%)–MnCO3/(X%)HRG (where X = 0–7), calcination at 400 °C and 500 °C, yielded different manganese oxides i.e., ZnOx(1%)–MnO2/(X%)HRG and ZnOx(1%)–Mn2O3/(X%)HRG respectively. The prepared catalyst were subjected to catalytic evaluation and a comparative catalytic study between carbonates and oxides for the liquid-phase aerobic oxidation of benzylic alcohols to corresponding aldehydes using molecular oxygen as an eco-friendly oxidant without adding additives or bases. The influence of various parameters such as percentage of HRG, reaction time, catalyst amount, calcination and reaction temperature was systematically examined to optimize reaction conditions using oxidation of benzyl alcohol as a substrate model. It was found that the catalytic performance is remarkably enhanced after using HRG as catalyst co-dopant for the aerobic oxidation of alcohols, possibly owing to the presence of carbon defects and oxygenated functional groups on HRG surface. The as-synthesized catalysts were characterized by SEM, EDX, XRD, Raman, TGA, BET, and FT-IR. Under optimal conditions, the catalyst with composition ZnOx(1%)–MnCO3/(1%)HRG calcined at 300 °C exhibited remarkable specific activity (57.1 mmol·g−1·h−1) with 100% conversion of benzyl alcohol and more than 99% product selectivity within extremely short time (7 min). The as-prepared catalyst was re-used up to five consecutive times without significant decrease in its activity and selectivity. To the best of our knowledge, the achieved specific activity is the highest so far compared to the earlier reported catalysts used for the benzyl alcohol oxidation. A wide range of substituted benzylic and aliphatic alcohols were selectively oxidized into their corresponding aldehydes with complete convertibility and selectivity in short reaction times without over-oxidation to the acids. Due to their significant low cost, superior reproducibility, excellent catalytic efficiency, the ZnOx(1%)–MnCO3/(X%)HRG nanocomposites possess several application prospect in other organic chemistry reactions.

Adsorption of methylene blue on modified electrolytic manganese residue: Kinetics, isotherm, thermodynamics and mechanism analysis

Abstract Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore. In this work, modified electrolytic manganese residue (MEMR) as a high-efficiency adsorbent for the removal of methylene blue (MB) was synthesized via hydrothermal method. The characterizations of MEMR were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption/desorption isotherms, and scanning electron microscope. The results showed that with the BET specific surface area of 500.8 m2/g the MEMR reached the maximum adsorption capacity (548.15 m2/g) within 50 min when the pH of initial solution was 6.05 and the initial concentration of MB was 1600 mg/L. The adsorption kinetics and equilibrium isotherms were accurately described by the pseudo-second-order model and Langmuir isotherm, respectively. The FTIR spectra indicated that electrostatic attraction and stacking interaction were the main adsorption mechanisms. Thermodynamic analyses showed that the adsorption of MB on MEMR was a spontaneous and exothermic physisorption process. This study revealed that MEMR can be used as a low cost and eco-friendly potential adsorbent for removing MB from wastewater.

Manganese carbonates in the Upper Jurassic Georgiev Formation of the Western Siberian marine basin

Manganese (Mn) carbonate rocks are a common lithological constituent of the Upper Oxfordian to Lower Tithonian (Volgian) Georgiev Formation of the Western Siberian marine basin (WSMB). The Mn carbonates in the Georgiev Formation are present in the form of massive sediments, stromatolites, and oncolites, and are associated with glauconite and partly also phosphate-rich clay- and siltstones. Unlike most Mn carbonates, they are not directly associated with organic-rich sediments, but occur below an organic-rich succession (Bazhenov Formation). The Mn carbonate occurrences can be traced from the western central area of the WSMB to its center along a distance of at least 750km. The thickness of the Mn carbonates and their Mn contents becomes reduced in an eastward direction, related to increased detrital input. The geochemical and mineralogical heterogeneity within the Mn carbonates indicates that they were deposited stepwise in a diagenetic regime characterized by steep gradients in Mn, Ca, and Mg. A first step consisted in the replacement of initial sediments within the microbialites during an early diagenetic stage, followed by a second step where massive sediments were transformed into Mn carbonate. During both steps, the decomposition of organic matter was an important source of the newly formed carbonate. During a further step, voids were cemented by Mn carbonates, which are rich in pyrite. This last generation may only have formed once the organic-rich sediments of the overlying Bazhenov Formation were deposited. Accumulation of the Mn carbonates in the Upper Jurassic WSMB was controlled by the proximity of Mn-enriched parent rocks, likely in the Ural, which were subjected to intense geochemical weathering during the Late Jurassic.

Gold, iron and manganese in central Amapá, Brazil

ABSTRACT: Greenstone belts with deposits of gold, iron and manganese are common in the Paleoproterozoic Maroni-Itacaiunas Tectonic Province of the Guiana Shield. In Brazil, in the State of Amapá and northwest of Pará, they are represented by the Vila Nova Group, constituted by a basal unit of metabasalts, covered by metasediments of clastic and chemical origin. The basal metasediments, the Serra do Navio Formation, are made of a cyclothem with lenses of manganese marbles at the top of each cycle. Under the intense weathering of the Amazon, these lenses were oxidized to large deposits of high-grade manganese oxides. The exploitation of these oxides left behind the manganese carbonates and low-grade oxides. The overlaying Serra da Canga Formation presents a calcium and magnesium domain grading to an iron domain with banded silicate and oxide iron formations, mined for iron ores. Overlapping structures and superposed metamorphic crystallizations indicate two phases of dynamothermal metamorphism, the first one with axis to north-northeast and the second one to northwest, with an intermediate phase of thermal metamorphism related to syntectonic granitic intrusions. Shears oriented north-south, possibly formed during the first dynamothermal metamorphism and reactivated in the second, are ideal sites for hydrothermalism and gold mineralization, which is greater when occurs in iron formation and carbonate-bearing rocks, as it happened at the Tucano mine. Layered mafic-ultramafic intrusions in the greenstones represent a potential for chromite and platinum group elements. Pegmatites are source of cassiterite and tantalite exploited from alluvial deposits.

Evaluation of engineered hydrochar from KMnO4 treated bamboo residues: Physicochemical properties, hygroscopic dynamics, and morphology

In this study, a novel approach was developed to prepare engineered hydrochar from KMnO4 treated bamboo residues through hydrothermal carbonization. The hydrochar yields were within a specified range of 61.8–67.8% at 180 °C and 39.8–45.0% at 260 °C, respectively. The higher temperature led to the higher C content, lower H/C and O/C ratio, whereas the ash content increased with increasing KMnO4 concentration, causing the increase of solid yield as well as the decrease of C content. Pseudo-second kinetic model was optimal to describe bamboo hydrochar’s hygroscopic dynamic, and the engineered hydrochar produced at 260 °C and 1.0 wt% concentration obtained the better hydrophobicity of 0.82%. SEM-EDS and XRD analysis confirmed the existence of manganese carbonate on the surface of engineered hydrochar, from which we inferred the chemical complexation between KMnO4 and hydrochar.

Potency of making the chemical manganese dioxide (CMD) from East Nusa Tenggara pyrolusite

Chemical manganese dioxide has not yet commercially developed in Indonesia. It is supplied by import sector. The fact that Indonesia has manganese resources as many as 60,893,820 tons is inconsistent with above condition. Research on CMD making employed pyrolusite as the raw material with size of - 100+150 mesh. The material was then reacted with sulfuric acid 6% and various concentration of molasses as reductant from 10, 20, 30, 50 and 100 %. The manganese sulfate leachate was then purified using sodium hydroxide and then filtered to have a nonferrous manganese sulfate. The Mn was precipitated from manganese sulfate using sodium bicarbonate. The precipitated manganese carbonate was then calcined at 600°C by injecting the air at various flow rates (100, 200, 300, 400 cc/minute) and different calcination time (2, 3, 4 hours) to get manganese dioxide. The best extracted Mn reached 97.58% using 50% of molasses as a reductant. The precipitation of manganese carbonate had produced sodium carbonate as an impurity. The calcination had not yet changed the manganese carbonate into manganese dioxide due to extremely high calcination temperature.

Improved hydrophilic property of PES/PEG/MnCO3 blended membranes for synthetic dye separation

Poly(ether sulfone) blended membranes were synthesized with various percentages of manganese carbonate as a surface modifier and poly(ethylene glycol) using a phase inversion technique. Surface characterization was made using scanning electron microscopy, atomic force microscopy and contact angle. The membrane equilibrium water content, porosity and average pore size were measured to evaluate the physical properties of the membrane. Performance of the blended membranes was evaluated in terms of water permeability, antifouling property and dye rejection efficiency. The membrane showed a significant change in surface morphology and hydrophilicity when 3 wt % MnCO3 was used. Water uptake tests confirmed the enhanced porous nature of the PES/PEG/MnCO3 blended membranes over the pristine PES membrane. Fouling studies showed that the 3 wt% MnCO3 blended membrane possesses an impressive 98% flux recovery ratio.

Fluoride adsorption on manganese carbonate: Ion-exchange based on the surface carbonate-like groups and hydroxyl groups

Manganese carbonate (MnCO3) nanowires and microcubes were controlled synthesized by a simple ethylene glycol (EG) mediated solution method. The volume ratios of EG and water has a decisive impact on the morphology of MnCO3 products. With a decreased water volume, MnCO3 products were transformed from microcubes to nanowires. The obtained MnCO3 nanowires were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption isotherm. The adsorption properties of the MnCO3 products towards fluoride were investigated. The adsorption capacities of the nanowires were higher than that of the microtubes. According to the Langmuir model, the maximum adsorption capacity was 46.80mgg−1 at pH 7.0. The adsorption capacity was 11.58mgg−1 when the equilibrium fluoride concentration was just below the WHO guideline of 1.5mgL−1. The kinetic data were well fitted to pseudo-second-order model. The fluoride removal was attributed to the ion-exchange based on the surface hydroxyl groups and carbonate-like groups, which was revealed by Fourier transform infrared absorption spectroscopy and X-ray photoelectron spectroscopy.

Controlled Synthesis of Homogeneous MnCO3 Hollow Nanostructures for Supercapacitor Application

Novel hollow nanospheres/cubes of MnCO3 nanostructures have been synthesized successfully by adopting co-precipitation method. Uniform hollow MnCO3 nanospheres/cubes was obtained by controlling the reaction kinetics in the nucleation process of forming manganese carbonates simply by employing NH4HCO3 and NH4SO4 as precipitating agents. Physicochemical and electrochemical performances of the hollow nanospheres/cubes MnCO3 samples are investigated by x-ray diffraction (XRD) scanning electron microscope with energy diffraction x-ray spectroscopy (EDXS), transmission electron microscopy (TEM) and electrochemical techniques. The results show that the hollow nanospheres/cubes of MnCO3 samples have a typical R-3C Rombohedral structure. Especially, the hollow MnCO3 nanosphere sample has excellent super capacitor performance. It delivers a specific capacity of 520 F/g between -0.3 and 0.9 V Vs SCE with capacity retention of 99 % over the 2000 cycles at a current density of 8 A/g at room temperature. Thus, the MnCO3 hollow nanosphere electrode will be a promising energy storage material for advanced supercapacitor applications. Figure 1