Mesoporous Manganese Oxide Research Articles

Metal cation and crystal lattice water molecule stabilized highly mesoporous manganese oxide network for excellent durable electrode in sodium-ion storage

Potassium birnessite is a remarkable material with a wider inter-planar spacing, which enables to accommodate more electrolytic ions to improve overall electrochemical performances. In this work, controlled synthesis of K0.46Mn2O4(H2O)1.4 (HKMO) nanosheets were interconnected mesoporous networks uniformly grown on carbon cloth (CC) via a one-step hydrothermal process. Specifically, the HKMO sample synthesized at 100 °C for 12 h (100@HKMO-12 h) exhibited a mesoporous morphology with a large specific surface area. The binder-free 100@HKMO-12 h electrode exhibits a maximum specific capacitance of 255F g−1 (323F cm−3) in 1 M NaClO4/acetonitrile electrolyte over a broad potential range of 3 V. DFT studies demonstrated the interlayer distance increased by the insertion of K+ ions into the MnO2 matrix. Bader charge analysis showed a 12.09 |e| charge difference for K-birnessite in the inter-layer region compared to the normal birnessite, supported the increase of inter-layer region in the MnO2 matrix. Significantly, the increased interlayer the distance, promoted rapid intercalation/deintercalation of Na+ ions and allowed the reversible faradic pseudocapacitance reaction to occur at a wider potential window. Moreover, the symmetric full-cell fabricated utilizing the 100@HKMO-12 h electrodes have a wide voltage of 2 V and the device delivered a maximum specific energy of 43 Wh kg−1 (28 Wh cm−3) at a minimum specific power of 556 W Kg−1 (349 W cm−3). Besides, the device showed an excellent capacitance retention of ∼94 % even after 10,000 continuous charge–discharge cycles at a current of 5 A/g, indicating it is a potential candidate for next-generation sodium energy storage devices.

Synthesis of perforated single-crystalline Mn2O3 microcubes for thermocatalytic applications

Perforated mesoporous manganese(iii) oxide microcubes (PMOM) were synthesized via morphology-conserved transformation of precursor method and enhanced surface reactions catalyse the decomposition of ammonium perchlorate, a solid propellant oxidizer.

Mesoporous Manganese Oxides with High-Valent Mn Species and Disordered Local Structures for Efficient Oxygen Electrocatalysis.

Active and nonprecious-metal bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital components of clean energy conversion devices such as regenerative fuel cells and rechargeable metal-air batteries. Porous manganese oxides (MnOx) are promising electrocatalyst candidates because of their high surface area and the abundance of Mn. MnOx catalysts exhibit various oxidation states and crystal structures, which critically affect their electrocatalytic activity. These effects remain elusive mainly because the synthesis of oxidation-state-controlled porous MnOx with similar structural properties is challenging. In this work, four different mesoporous manganese oxides (m-MnOx) were synthesized and used as model catalysts to investigate the effects of local structures and Mn valence states on the activity toward oxygen electrocatalysis. The following activity trends were observed: m-Mn2O3 > m-MnO2 > m-MnO > m-Mn3O4 for the ORR and m-MnO2 > m-Mn2O3 > m-MnO ≈ m-Mn3O4 for the OER. These activity trends suggest that high-valent Mn species (Mn(III) and Mn(IV)) with disordered atomic arrangements induced by nanostructuring significantly influence electrocatalysis. In situ X-ray absorption spectroscopy was used to analyze the changes in the oxidation states under the ORR and OER conditions, which showed the surface phase transformation and generation of active species during electrocatalysis.

Nickel-doped mesoporous manganese oxides for enhanced peroxymonosulfate-based oxidation of tetracycline hydrochloride: Performance and mechanism

The modified inverse micelle approach was used to create nickel-doped mesoporous manganese oxides (Ni-MM). These novel catalysts showed much higher reactivity to activating PMS than the pristine mesoporous manganese oxides, and 5% doping ratio (Ni/Mn) would lead to best degradation efficiency in the PMS/Ni-MM system. X-ray diffraction (XRD) displayed that the crystal composition of manganese oxides would be changed and scanning electron microscope (FESEM) presented that the surface morphology was transformed from spherical deconstruction to sponge-like particles since Ni was doped into MM. Mn2+, Mn3+ and Mn4+ were coexisted in 5%Ni-MM, and Ni in the material was +2. The operating conditions such as catalyst dosage, PMS dosage, TCH concentration and beginning pH. Under the ideal reaction conditions for 5%Ni-MM/PMS system, the TCH degradation efficiency could be 86.79% in 30 min, and it could be used in the pH range (3-11). In the presence of Cl−, SO42−, CO32−, PO43−, HCO3−, humic acid (HA) and natural water bodies, TCH degradation efficiencies could still be greater than 80%. Quenching experiments indicated that O2·-, 1O2, SO4·- and ·OH contributed to TCH degradation in the 5%Ni-MM/PMS system. The intermediates were identified by LC-MS, and the pathways for 5%Ni-MM/PMS system degradation of TCH were conjectured.

Synthesis and characterization of high surface area mesoporous manganese oxides nanofibers prepared by electrospinning technique

Synthesis and characterization of high surface area mesoporous manganese oxides nanofibers prepared by electrospinning technique

Allylic and Benzylic Alcohol Coupling Reactions Catalyzed by Lithium-Promoted Manganese Oxides

This study reports a novel methodology for the production of allyl acrylate from allyl alcohol solely as the starting substrate. The reaction reported here utilizes a heterogeneous reusable catalyst based on Li-ion-promoted mesoporous manganese oxide. The reaction conditions are mild (ambient pressure and temperature of 80 °C). The catalytic activity, selectivity, and substrate scope of the reaction are reported (60% yield). The system proposed here is composed of an allylic alcohol substrate, O2 as the oxidant, N-hydroxyphthalimide (NHPI) as the promoter, and trichloro acetonitrile (CCl3CN) as the solvent together with the Li-promoted manganese oxide (surface area >150 m2/g) as the catalyst.

Oral Nanomotor-Enabled Mucus Traverse and Tumor Penetration for Targeted Chemo-Sono-Immunotherapy against Colon Cancer.

The therapeutic outcomes of oral nanomedicines against colon cancer are heavily compromised by their lack of specific penetration into the internal tumor, favorable anti-tumor activity, and activation of anti-tumor immunity. Herein, hydrogen peroxide (H2 O2 )/ultrasound (US)-driven mesoporous manganese oxide (MnOx )-based nanomotors are constructed by loading mitochondrial sonosensitizers into their mesoporous channels and orderly dual-functionalizing their surface with silk fibroin and chondroitin sulfate. The locomotory activities and tumor-targeting capacities of the resultant nanomotors (CS-ID@NMs) are greatly improved in the presence of H2 O2 and US irradiation, inducing efficient mucus-traversing and deep tumor penetration. The excess H2 O2 in the tumor microenvironment (TME) is decomposed into hydroxyl radicals and oxygen by an Mn2+ -mediated Fenton-like reaction, and the produced oxygen participates in sonodynamic therapy (SDT), yielding abundant singlet oxygen. The combined Mn2+ -mediated chemodynamic therapy and SDT cause effective ferropotosis of tumor cells and accelerate the release of tumor antigens. Importantly, animal experiments reveal that the treatment of combining oral hydrogel (chitosan/alginate)-embedding CS-ID@NMs and immune checkpoint inhibitors can simultaneously suppress the growth of primary and distal tumors through direct killing, reversion of immunosuppressive TME, and potentiation of systemic anti-tumor immunity, demonstrating that the CS-ID@NM-based platform is a robust oral system for synergistic treatment of colon cancer.

Comparative study of the performance of controlled release materials containing mesoporous MnOx in catalytic persulfate activation for the remediation of tetracycline contaminated groundwater

Controlled release materials (CRMs) are an emerging oxidant delivery technique for in-situ chemical oxidation (ISCO) that solve the problems of contaminant rebound, backflow and wake during groundwater remediation. CRMs were fabricated using ordered mesoporous manganese oxide (O-MnOx) and sodium persulfate (Na2S2O8) as active components, for the removal of antibiotic pollutants from groundwater. In both static and dynamic groundwater environments, persulfate can first be activated by O-MnOx within CRMs to form sulfate radicals and hydroxyl radicals, with these radicals subsequently dissolving out from the CRMs and degrading tetracycline (TC). Due to their excellent persulfate activation performance and good stability, the constructed CRMs could effectively degrade TC in both static and dynamic simulated groundwater systems over a long period (>21 days). The TC removal rate reached >80 %. Changing the added content of O-MnOx and persulfate could effectively regulate the performance of the CRMs during TC degradation in groundwater. The process and products of TC degradation in the dynamic groundwater system were the same as in the static groundwater system. Due to the strong oxidizing properties of sulfate radicals and hydroxyl radicals, TC molecules were completely mineralized within the groundwater systems, resulting in only trace levels of degradation products being detectable, with low- or non-toxicity. Therefore, the CRMs constructed in this study exhibited good potential for practical application in the remediation of organic pollutants from both static and dynamic groundwater environments.

Inverse micelle fabrication of ordered mesoporous manganese oxide and degradation of tetracycline hydrochloride

Ordered mesoporous manganese oxides (MnOx) were synthesized using the modified inverse micelle method. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The element content and changes in surface valence of catalysts were analyzed by X-ray photoelectron spectroscopy (XPS). The MnOx were used to activate peroxymonosulfate (PMS) to degrade tetracycline hydrochloride (TCH). The catalytic activity of MnOx was enhanced at a calcination temperature of 350 °C (MM-3). The degradation efficiency of TCH in MM-3/PMS system was 87.89% in 180 min. Appropriate dosages of catalyst and PMS improve the degradation efficiency of TCH. This system showed a wide range of pH application (3–9). In the presence of coexisting ions and humic acid, the degradation efficiency of TCH was still above 80%. The results of free radical capture experiment and electron paramagnetic resonance (EPR) test proved that the system activates PMS to produce three types of free radicals: SO4−, OH and 1O2. Therefore, MM-3 is a promising catalyst for the degradation of TCH in practical wastewater treatment.

Hollow Mesoporous Manganese Oxides: Application in Cancer Diagnosis and Therapy.

The precision, minimal invasiveness, and integration of diagnosis and treatment are critical factors for tumor treatment at the present. Although nanomedicine has shown the potential in tumor precision treatment, nanocarriers with high efficiency, excellent targeting, controlled release, and good biocompatibility still need to be further explored. Hollow mesoporous manganese oxides nanomaterials (HM-MONs), as an efficient drug delivery carrier, have attracted substantial attention in applications of tumor diagnosis and therapy due to their unique properties, such as tumor microenvironment stimuli-responsiveness, prominent catalytic activity, excellent biodegradation, and outstanding magnetic resonance imaging ability. The HM-MONs can not only enhance the therapeutic efficiency but also realize multimodal diagnosis of tumors. Consequently, it is necessary to introduce applications based on HM-MONs in cancer diagnosis and therapy. In this review, the representative progress of HM-MONs in synthesis is discussed. Then, several promising applications in drug delivery, bio-imaging, and bio-detection are highlighted. Finally, the challenges and perspectives of the anticancer applications are summarized, which is expected to provide meaningful guidance on further research.

Effective removal of methylene blue using nanoscale manganese oxide rods and spheres derived from different precursors of manganese

Nanoscale manganese oxide with different morphologies were developed at room temperature using different precursor salts (potassium permanganate and manganese sulfate). The obtained nanoscale morphologies, i.e., rod and sphere-shaped were characterized using BET surface area analyzer, SEM, TEM, and XRD. The manganese oxide possessed the rod and sphere-like morphologies with different pore structures. The adsorption of methylene blue on mesoporous manganese oxide followed the pseudo-second-order kinetics and best fitted with the Freundlich adsorption isotherm model with a removal capacity of 2914 mg g−1. The effect of irradiation time on degradation efficiency was also examined, which followed the first-order kinetics with a degradation efficiency of 93.12%. Furthermore, the recycling studies revealed that the spherical manganese oxide retained over 90% of the photodegradation efficiency after three cycles of methylene blue degradation, which proves its stability for practical applications. Therefore, mesoporous manganese oxide with significant adsorption and remarkable photodegradation capability can provide a way forward to fine-tune the material's properties for effective environmental remediation.

Catalytic ozonation of ethyl acetate over mesoporous manganese oxides synthesized by a sonochemical method

AbstractEthyl acetate is one of typical volatile organic compounds (VOCs) emitting from solvent use, and removing ethyl acetate from exhaust air is vital to VOCs abatement. The mesoporous manganese oxide (MnOx) samples were sonochemically synthesized by the reduction of KMnO4 using Mn(NO3)2. The characterization shows that γ‐MnO2, β‐MnO2, and bixbyite‐like Mn2O3 were obtained by calcining the MnOx samples from 200°C to 500°C. The results show that γ‐MnO2 and β‐MnO2 possess more Mn4+ than bixbyite‐like Mn2O3. β‐MnO2 has the highest contents of surface oxygen species (Oads) and average oxidation state (AOS) among the MnOx catalysts. Based on a 7‐day test, β‐MnO2 performed the highest activity for the catalytic ozonation of ethyl acetate compared with the other MnOx catalysts. The results show that ethyl acetate is easy to be destroyed but difficult to be completely mineralized by catalytic ozonation. Lower gas hourly space velocity (GHSV) leads to higher CO2 selectivity and more intermediate products form in the catalytic ozonation of ethyl acetate under higher GHSV. A further study indicates that β‐MnO2 has a long‐term stability for catalytic ozonation of ethyl acetate because the accumulation and the decomposition of intermediate products are in a dynamic equilibrium during the catalytic ozonation.

Synthesis and characterization of novel metal chalcogenide modified Ni-Co-MnO2 nanofibers rolled with graphene based visible light active catalyst for nitro phenol degradation

Nickel-cobalt (Ni-Co) metal ion modified manganese oxide is prepared by a surfactant-assisted precipitation method through the in situ-doping into manganese oxide matrix. The prepared manganese oxide showed good porous property and improved surface area values and was further impregnated via reducing graphene oxide by an ultrasonication-assisted deposition method. The nanocomposite was decorated by adding commercial MoS2 nanoparticles to fabricate the binary nanocomposite. The thermal stability of the as-prepared sample was stable up to 450−500 °C in an air atmosphere and a negative zeta potential was obtained for most of the prepared nanocomposite sample. MoS2nanoparticle appeared as spherical nanoparticle at a smaller particle size formation (10−20 nm) on porous Ni-Co-MnOx surfaces, and nanoparticle deposition and graphene nanosheets act as a structure-directing agent toward layered nanotubes morphology formation for mesoporous manganese oxide. The as-prepared binary nanocomposite was further tested for toxic catalytic nitrophenol degradation under visible light exposure condition.

Synthesis and characterization of metal chalcogenide modified graphene oxide sandwiched manganese oxide nanofibers on nickel foam electrodes for high performance supercapacitor applications

Nanoparticles of metal chalcogenide (MoS2) are incorporated on reduced graphene oxide nano sheet rolled mesoporous manganese oxide were prepared by feasible ultrasonic assisted deposition technique. The above prepared nanocomposite is further coated on Nickel foam substrate for direct application towards high performance supercapcitor energy storage application. The detailed studies of surface and textural property such as crystalline phase stability, surface structure, particle size, zeta potential measurements have been explained for all prepared nanocomposite samples. The crystalline phase of as prepared mesoporous manganese oxide is forms the mixed phase of Mn2O3 bixbyite phase. The thermal stability of as prepared sample improved up to 400 °C in oxygen atmosphere and negative zeta potential obtained for all prepared nanocomposite sample. The different amount of MoS2 nanoparticle (10 mg −100 mg range) was utilized to study the effect of molybdenum sulphide (additive) addition on graphene oxide rolled mesoporous manganese oxide nanofiber matrix. Increased quantity of MoS2 addition increase the electrochemical supercapacitance value of the nanocomposite coated nickel foam based electrode. Nanofibers morphology of mesoporous manganese oxide with reduced graphene oxide is visibly seen in the TEM images. Needle like metallic rich shapes are also obtained due to MoS2 nanoparticle existence and it inserted in the Nanofiber/graphene sheet structure. The higher supercapacitance values are obtained for Nickel foam modified MoS2 deposited graphene oxide rolled MnOx nanocomposite (980 and 788 F/g) under acidic electrolyte medium and charge/discharge cycle stability have also been studied for all prepared nanocomposites.

Sacrificial template-directed fabrication of mesoporous manganese oxide based catalysts: Relationship between the ordering degree of pore structure and Fenton-like catalytic activity

In this study, novel mesoporous MnOx-based catalysts were prepared via the hard template method by using the mesoporous silica as a template. The performances of these catalysts were evaluated in catalytic wet H2O2 oxidation for Rhodamine B (RhB) in high-salinity wastewater (10% Na2SO4 solution containing RhB). The microstructure characterization indicated that the order of pore structures and the MnOx crystallinity in mesoporous materials improved as the number of repetitions of the immersion and calcination–molding process increased. Given good selective adsorption performance for RhB and rich Mn3+/Mn4+ couples, MnOx mesoporous materials with ordered regular pores exhibited excellent Fenton-like catalytic performance and the highest removal rate of RhB in high-salinity wastewater reached approximately 90% after 150 min of degradation. Moreover, because of the accelerated generation of the free radicals catalyzed by the Fe3+/Fe2+ couples, the loading of Fe species increased the performance of the MnOx ordered catalysts for RhB degradation. Furthermore, the Fe-loading MnOx catalyst exhibited only slight activity loss within the five cycles of catalytic degradation (the removal rate for RhB within the five cycles all exceeded 95%), due to the morphological stability of the MnOx ordered catalyst and the presence of stable Fe3+/Fe2+ couples during the RhB degradation process.

PREPARATION AND STRUCTURAL CHARACTERIZATION OF MoS2 NANOPARTICLE COATED GRAPHENE OXIDE/MANGANESE OXIDE COMPOSITE FOR ENERGY STORAGE APPLICATION

Nanoparticles of powder molybdenum sulphide (MoS2) are deposited on reduced graphene oxide-mesoporous manganese oxide nanocomposite which is represented as MoSGMn were prepared by feasible ultrasonic assisted deposition technique. The above prepared nanocomposite is further coated on Nickel foam substrate for direct application towards supercapacitor electrode fabrication. The detailed studies of thermal property and surface property such as thermal stability, surface structure and zeta potential measurements have been explained for all prepared nanocomposite samples. The thermal stability of as prepared sample stable upto 350 oC in oxygen atmosphere and negative zeta potential obtained for all prepared nanocomposite sample. The different amount of MoS2 nanoparticle (10mg -100 mg range) was utilized to study the effect of molybdenum sulphide addition on major mesoporous manganese oxide matrix. Increased quantity of MoS2 addition increase the electrochemical supercapacitance value of the nanocomposite coated nickel foam modified electrode.

Template-free Synthesis of Mesoporous and Crystalline Transition Metal Oxide Nanoplates with Abundant Surface Defects

Summary Mesoporous transition metal oxides with crystalline walls show promising applications in catalysis and energy storage. Syntheses of those crystalline mesoporous oxides, however, currently remain as an unmet challenge because of the large volume shrinkage during crystallization in a sol-gel process. Here, we demonstrate a facile and general template-free method to prepare six mesoporous transition metal oxides, e.g., CuO, CoO, and spinel MCo2O4 (M = Co, Cu, Mn, Zn), with highly crystalline walls and continuous mesopores in the forms of two-dimensional nanoplates or nanosheets. The method is based on the thermal crystalline transformation from basic carbonates to mesoporous metal oxides. The crystal interconversion not only endows the crystallinity and mesoporosity of oxides but also generates abundant surface-step defects that show remarkable enhancement of the catalytic activity of porous oxides. Our method likely provides an alternative paradigm for cost-effective and universal synthesis of crystalline mesoporous oxides beyond the traditional templating methods.

Magnetic Manganese Oxide Sweetgum-Ball Nanospheres with Large Mesopores Regulate Tumor Microenvironments for Enhanced Tumor Nanotheranostics.

An important objective of cancer nanomedicine is to improve the delivery efficacy of functional agents to solid tumors for effective cancer imaging and therapy. Stimulus-responsive nanoplatforms can target and regulate the tumor microenvironment (TME) for the optimization of cancer theranostics. Here, we developed magnetic manganese oxide sweetgum-ball nanospheres (MMOSs) with large mesopores as tools for improved cancer theranostics. MMOSs contain magnetic iron oxide nanoparticles and mesoporous manganese oxide (MnO2) nanosheets, which are assembled into gumball-like structures on magnetic iron oxides. The large mesopores of MMOSs are suited for cargo loading with chlorin e6 (Ce6) and doxorubicin (DOX), thus producing so-called CD@MMOSs. The core of magnetic iron oxides could achieve magnetic targeting of tumors under a magnetic field (0.25 mT), and the targeted CD@MMOSs may decompose under TME conditions, thereby releasing loaded cargo molecules and reacting with endogenous hydrogen peroxide (H2O2) to generate oxygen (O2) and manganese (II) ions (Mn2+). Investigation in vivo in tumor-bearing mice models showed that the CD@MMOS nanoplatforms achieved TME-responsive cargo release, which might be applied in chemotherapy and photodynamic therapy. A remarkable in vivo synergy of diagnostic and therapeutic functionalities was achieved by the decomposition of CD@MMOSs and coadministration with chemo-photodynamic therapy of tumors using the magnetic targeting mechanism. Thus, the result of this study demonstrates the feasibility of smart nanotheranostics to achieve tumor-specific enhanced combination therapy.

Aerobic Self‐Esterification of Alcohols Assisted by Mesoporous Manganese and Cobalt Oxide

AbstractAerobic self‐esterification of primary alcohols catalyzed by mesoporous metal oxides (manganese and cobalt oxides) is reported under base and solvent free conditions. For a range of aliphatic alcohols, up to 90 % conversions to esters was achieved. The catalytic reaction is likewise applicable to neat aldehydes as substrates with yields of up to 86 %. High pressure batch reaction for ethanol to ethyl acetate led to 22 % yield. Isotope labeling studies indicated decarboxylation on the catalyst surface. Mechanistic and kinetic experiments implicate oxygen rebound and α‐carbon removal as intermediate steps. Mesoporous cobalt oxide showed about 20 % higher catalytic activity compared to mesoporous manganese oxide.

Surfactant selection as a strategy for tailoring the structure and properties of UCT manganese oxides

Mesoporous manganese oxides were synthesized using the UCT inverse micelle templating method with four different Pluronic surfactants to investigate the effects on the morphology, microstructure and desulfurization behavior of these materials. All of the as-synthesized samples exhibited similar hierarchical microstructures, but the size and shape of the primary nanoparticles for each sample was different. The primary nanoparticle sizes for these samples vary between 2.3 and 7.0 nm. Most of the samples are crystalline and are composed of a mixture of Mn3O4 and Mn5O8 phases. The adsorption behavior of these samples was tested using a fixed bed reactor at a temperature of 200 °C. Microstructural analysis of the samples after the desulfurization tests revealed a transformation of the mesoporous manganese oxide to a dense manganese sulfide phase; this involves a volumetric expansion of the crystal, leading to densification and a rapid decay in the sorption capacity after the breakthrough point. The variation in the structure and properties of these materials is related to ratio of the PEO and PPO chain segment lengths in the Pluronic surfactants used. This indicates that the ratio must dictate the volume, shape and assembly of the inverse micelles in the UCT synthesis.