Morphology and Crystallinity-controlled Synthesis of Manganese Cobalt Oxide/Manganese Dioxides Hierarchical Nanostructures for High-Performance Supercapacitors

We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.

An amorphous manganese iron oxide hollow nanocube cathode for aqueous zinc ion batteries

Aqueous zinc ion batteries(ZIBs) are attracting considerable attentions for practical energy storage because of their low cost and high safety.Nevertheless,the traditional manganese oxide cathode materials suffer from the low intrinsic electronic conductivity,sluggish ions diffusion kinetics,and structural collapse,hindering their large-scale application.Herein,we successfully developed a latent amorphous Mn_(1.8)Fe_(1.2)O_(4) hollow nanocube(a-H-MnFeO) cathode material derived from Prussian blue analogue precursor.The amorphous nature endows the cathode with lower diffusion barrier and narrower band gap compared with crystalline counterpart,resulting in the superior Zn^(2+) ions and electrons transport kinetics.Hollow structure can furnish abundant surface sites and suppress the structural collapse during the repeated charge/discharge processes.By virtue of the multiple advantageous features,the a-H-MnFeO cathode exhibits exceptional electrochemical performance,in terms of high capacity,excellent rate capability,and prolonged cycle life.This strategy will pave the way for the structural design of emerging cathode materials.

Formation of Platinum (Pt) Nanocluster Coatings on K-OMS-2 Manganese Oxide Membranes by Reactive Spray Deposition Technique (RSDT) for Extended Stability during CO Oxidation

Nanocluster formation of a metallic platinum (Pt) coating, on manganese oxide inorganic membranes impregnated with multiwall carbon nanotubes (K-OMS-2/MWCNTs), applied by reactive spray deposition technology (RSDT) is discussed. RSDT applies thin films of Pt nanoclusters on the substrate;the thickness of the film can be easily controlled. The K-OMS-2/MWCNTs fibers were enclosed by the thin film of Pt. X-ray diffraction (XRD), scanning electron microscopy/X-ray energy dispersive spectroscopy (SEM/XEDS), focus ion beam/scanning electron microscopy (FIB/SEM), transmission electron microscopy (TEM), and X-ray 3D micro-tomography (MicroXCT) which have been used to characterize the resultant Pt/K-OMS-2/MWCNTs membrane. The non-destructive characterization technique (MicroXCT) resolves the Pt layer on the upper layer of the composite membrane and also shows that the membrane is composed of sheets superimposed into stacks. The nanostructured coating on the composite membrane material has been evaluated for carbon monoxide (CO) oxidation. The functionalized Pt/K-OMS-2/MWCNTs membranes show excellent conversion (100%) of CO to CO2 at a lower temperature 200℃ compared to the uncoated K-OMS-2/MWCNTs. Moreover, the Pt/K-OMS-2/MWCNTs membranes show outstanding stability, of more than 4 days, for CO oxidation at 200℃.

Citrate-promoted dissolution of nanostructured manganese oxides:Implications for nano-enabled sustainable agriculture

Nanostructured manganese oxides (nano-MnO_(x)) have shown great promises as versatile agrochemicals in nano-enabled sustainable agriculture,owing to the coupled benefits of controlled release of dissolved Mn2+,an essential nutrient needed by plants,and oxidative destruction of environmental organic pollutants.Here,we show that three δ-MnO_(2)nanomaterials consisting of nanosheet-assembled flower-like nanospheres not only exhibit greater kinetics in citrate-promoted dissolution,but also are less prone to passivation,compared with three α-MnO_(2)nanowire materials.The better performance of the δ-MnO_(2)nanomaterials can be attributed to their higher abundance of surface unsaturated Mn atoms–particularly Mn(Ⅲ)–that is originated from their specific exposed facets and higher abundance of surface defects sites.Our results underline the great potential of modulating nanomaterial surface atomic configuration to improve their performance in sustainable agricultural applications.

MnHCF/MnO_2 Core-shell Nanostructures as Cathode Material for Supercapacitors with High Energy Density

A nanocomposite of manganese dioxide coated manganese hexacyanoferrate was synthesized by a facile co-precipitation method and tested as active electrode material for an electrochemical supercapacitor. A way called "Deep electro-oxidation" was used to generate manganese dioxide coated layer for stabilizing the electrode material. The structure and ingredient of the resulting MnHCF/MnO2 composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray Photoelectron Spectroscopy. Electrochemical testing showed a capacitance of 225.6 F/g at a sweep rate of 5 mV/s within a voltage range of 1.3 V, and high energy density of 37.2 Wh/kg at a current density of 0.5 A/g in galvanostatic charge/discharge cycling. It is suggested that the two different components, manganese hexacyanoferrate core and manganese dioxide shell, lead to an integrated electrochemical behavior, and an enhanced capacitor. The electrochemical testing and corresponding XPS analysis also demonstrated that the manganese coordinated by cyanide groups via nitrogen atoms in MnHCF did not get involved in the charge storage process during potential cycles.

界面效应在锰氧化物修饰的CeO_(2)纳米立方甲苯氧化中的作用

本研究通过水热-浸渍两步法成功制备了不同Mn负载量的二元xMn/Ce(xMnOx/CeO_(2))催化剂,并评估了催化剂在甲苯催化氧化反应中的性能。研究结果表明,引入MnOx能显著提高催化剂的甲苯氧化活性。特别是当Mn负载量为10%(10Mn/Ce)时,在气体空速为60000 mL/(g·h)的条件下,t90(甲苯转化率达到90%时的温度)仅为233℃,显示出最优的甲苯催化氧化活性。这一结果说明,适量加入MnOx能够显著提高催化剂的催化性能。通过X射线衍射(XRD)、拉曼光谱(Raman)、透射电子显微镜(TEM)、程序升温还原(H2-TPR)和X射线光电子能谱(XPS)等表征手段,发现MnOx的加入在MnOx与CeO_(2)之间形成了界面效应,这显著改变了Mn/Ce催化剂的物理化学性质。由于界面效应的作用,不仅提高了10 Mn/Ce催化剂中Ce3+、Mn3+离子的浓度以及氧空位的浓度,而且还降低了催化剂表面Ce−O键强度,使得表面晶格氧更易于参与甲苯的催化氧化,提升了催化剂的氧化还原性能,从而促进了甲苯的催化氧化。本研究不仅成功制备了具有优异甲苯氧化活性的Mn/Ce催化剂,而且揭示了其背后的界面效应机制,为VOCs高效氧化催化剂设计与制备提供了简单有效的方法与思路。

Controlled synthesis of porous spinel cobalt manganese oxides as efficient oxygen reduction reaction electrocatalysts

In this article, we report a facile precursor pyrolysis method to prepare porous spinel-type cobalt manganese oxides （CoxMng-xO4） with controllable morphologies and crystalline structures. The capping agent in the reaction was found to be crucial on the formation of the porous spinel cobalt manganese oxides from cubic Co2MnO4 nanorods to tetragonal CoMn2O4 microspheres and tetragonal CoMn204 cubes, respectively. All of the prepared spinel materials exhibit brilliant oxygen reduction reaction （ORR） electrocatalysis along with high stability. In particular, the cubic Co2MnO4 nanorods show the best performance with an onset potential of 0.9 V and a half-wave potential of 0.72 V which are very close to the commercial Pt/C. Meanwhile, the cubic Co2MnO4 nanorods present superior stability with negligible degradation of their electrocatalytic activity after a continuous operation time of 10,000 seconds, which is much better than the commercial Pt/C electrocatalvst.

Recent advances in water-splitting electrocatalysts based on manganese oxide

The oxygen evolution reaction(OER)of electrochemical water splitting represents a source of hydrogen(H_(2))energy.Precious-metal-based RuO_(x)and IrO_(x)are expensive and degrade in the presence of electrolyte;thus,the development of low-cost and eco-friendly OER electrocatalysts is needed.This review summarizes the recent status of the nonprecious manganese metal-oxide-based electrocatalysts with reference to nanostructure,defect engineering,hybrid composite formation,and core-shell formation to achieve efficient OER performance.In particular,we focus on the strategies used to lower the onset potential and the Tafel slope of the water oxidation process.Future prospects for the development of manganese-oxide-based electrocatalysts are discussed.

锰氧化物材料的制备及应用进展

锰作为一种常见的变价金属,其在催化反应中能够起到很好的催化作用。而且锰的氧化物作为最常用的过渡金属氧化物之一,因其较易调控出较大的比表面积、较强的吸附性能、较好的氧化还原能力以及较好的低温催化活性,已经成为了环境治理以及能源领域中的研究热点。介绍了MnO_x催化剂材料的合成、性质,以及在CO催化氧化、挥发性有机污染物的催化氧化、气体的吸附与分离以及电池的电极材料等应用方面一些最新的研究进展。

纳米二氧化锰的电化学电容性能

以MnSO4和K2S2O8为原料，采用液相法制得MnO2并制成电化学电容器电极；采用X射线衍射和扫描电镜对产物进行结构形貌表征，采用恒流充放电、循环伏安、交流阻抗等方法对MnO2电化学电容器电化学性能进行表征。研究结果表明：产物为纳米棒聚集而形成的纳米α-MnO2。充放电曲线由于电极在0．53V和0．36V（vs．Hg／HgO）处发生氧化还原反应而发生了明显弯曲，这有利于比容量的提高；在10^-3～10^4Hz频率范围内，阻抗曲线在0．2Hz以下出现“电荷饱和”，说明电极材料中储存的大部分电容量可得到利用，有效能量为48．3J／g，电极具有良好的倍率特征，其频率响应时间为12．5s；在低频区电极过程由阻挡层扩散控制，比容量可达到151F／g，但随着频率增加，比容量快速下降，100Hz以后比容量开始趋于0。

系列纳米结构锰氧化物的水热合成(英文)

以KMnO4为锰源、抗坏血酸(AA)为还原剂,采用水热法制备系列纳米结构锰氧化物。通过调节反应物的物质的量的比、水溶液的pH值、反应温度和反应时间,制备出了不同纳米结构的锰氧化物,包括Mn3O4纳米粒子、MnOOH、α-MnO2和β-MnO2纳米棒。采用XRD和TEM测试技术对合成产物进行了表征,同时对其反应机理进行了探讨。

从Mn_3O_4前驱体到MnO_2纳米结构的形貌和结构变化(英文)

锰氧化物是一类重要的且具有广泛应用背景的材料,控制合成不同形貌和组成的锰氧化物纳米结构将有助于拓宽其应用领域.本文报道了以Mn3O4为前驱体,通过水热法控制合成MnO2纳米结构的方法.用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等手段对产物进行表征.在硫酸体系中,当反应温度为80和180℃时,所得产物分别为γ-MnO2海胆结构和β-MnO2单晶纳米棒.此外,MnOOH纳米线可以在稀酸溶液中合成.考察了反应温度、溶液酸度、反应时间对产物结构的影响,并提出了基于γ-MnO2为中间产物的反应机理.实验结果表明,水热体系促进了产物的各向异性生长并最终形成不同形貌和结构的锰氧化物.

采用简单化学沉积制备纳米锰氧化物及其电化学超级电容性能(英文)

通过一种简便的化学沉积的方法，合成了用于电化学超级电容器的纳米锰氧化物材料．采用扫描电镜（SEM）、透射电镜（TEM）和X-射线衍射（XRD）对材料的形貌及其结构进行了表征．通过循环伏安、恒电流充放电以及电化学交流阻抗等对材料的电化学性能进行了测试，结果为：所制备的材料在6mol·L^-1KOH的电解质体系中、在5mV·s^-1的扫描速率下具有266F·g^-1的比容量，对比文献报道值150～250F·g^-1有明显的提高．且材料具有较好的电化学稳定性和较长的循环寿命．

二氧化锰一维纳米结构的制备

二氧化锰广泛用作催化剂、分子筛以及电池的正极材料。文章以Mn(NO3)2为锰源、NaClO3为氧化剂,在水热条件下,通过改变反应条件合成一系列不同径向比的二氧化锰纳米晶体;并讨论了反应条件的改变对所得到的纳米晶体形貌的影响。

MnO_2/NiCo_2O_4复合材料的控制合成及其电化学性能研究

采用两步合成法制备了MnO_2/NiCo_2O_4核壳结构纳米棒,使用场发射扫描电子显微镜、X射线衍射和电化学工作站研究了其形貌特征和电化学性能。研究结果表明,在α-MnO_2纳米棒上生长了均匀的NiCo_2O_4纳米片,这种核壳结构纳米棒所制备的电极在充放电电流密度为0.5A/g时比电容达到了434F/g,明显比纯α-MnO_2的比电容(256F/g)高,循环测试2 000次后,比电容保留量为91.8%,表现出了优秀的电化学性能,具有广阔的应用前景。

锰氧化物的合成及在锂离子电池中的应用进展

能源是限制人类发展的重要因素,近年来随着新能源的发展,人们对于储能设备的要求也越来越高,其中,锂离子电池被认为是最具有发展前途的储能设备之一。目前,商用锂离子电池的负极材料以石墨为主,石墨虽然具有良好的导电性,但理论容量较低,已逐渐无法满足高能设备的大容量需求。过渡金属锰氧化物由于储量丰富、氧化形态多样、结构多元、理论比容量高、环境友好等特点,被认为是锂离子电池理想的替代负极材料之一。本文详细介绍了近年来4种锰氧化物(MnO、Mn_(2)O_(3)、Mn_(3)O_(4)和MnO_(2))分别在纳米化和复合结构构筑两方面的材料设计及合成,总结比较了4种锰氧化物用作锂离子电池负极材料的性能,展望了锰氧化物在锂离子电池负极材料领域的发展前景和方向。

Molten salt synthesis of α-MnO_(2)/Mn_(2)O_(3) nanocomposite as a high-performance cathode material for aqueous zinc-ion batteries

Thanks to low cost,high safety,and large energy density,aqueous zinc-ion batteries have attracted tremendous interest worldwide.However,it remains a challenge to develop high-performance cathode materials with an appropriate method that is easy to realize massive production.Herein,we use a molten salt method to synthesize nanostructured manganese oxides.The crystalline phases of the manganese oxides can be tuned by changing the amount of reduced graphene oxide added to the reactant mixture.It is found that the α-MnO_(2)/Mn_(2)O_(3) nanocomposite with the largest mass ratio of Mn_(2)O_(3) delivers the best electrochemical performances among all the products.And its rate capability and cyclability can be significantly improved by modifying the Zn anode with carbon black coating and nanocellulose binder.In this situation,the nanocomposite can deliver high discharging capacities of 322.1 and 213.6 mAh g^(-1) at 0.2 and 3 Ag^(-1),respectively.After 1000 cycles,it can retain 86.2% of the capacity at the 2 nd cycle.Thus,this nanocomposite holds great promise for practical applications.

纳米二氧化锰的制备及其应用研究进展

二氧化锰作为一种重要的过渡金属氧化物,因其储量丰富、晶型多样、性能优异而备受关注。将二氧化锰纳米化后,其颗粒尺寸变小、比表面积变大、材料性能优化、应用领域得以拓宽。本文在引言部分从介绍二氧化锰的应用着手,指出纳米化和晶型多变对二氧化锰的结构和性能有着重要的影响。正文部分主要从纳米二氧化锰的制备方法和纳米二氧化锰的应用两个方面对近年来的研究进展进行了总结和评述。(1)介绍了水热法、溶胶-凝胶法、化学沉淀法、固相合成法等纳米二氧化锰的制备方法,对各种制备方法的优点与缺点以及所制备纳米二氧化锰的形貌与性能进行了总结。(2)综述了纳米二氧化锰在储能电极、电致变色器件、催化剂、生物传感器等领域的应用研究进展。纳米二氧化锰可作为电池的正极材料和超级电容器的电极材料。通过调控二氧化锰的晶型和复合制备的含锰复合氧化物用于锂离子电池的正极材料,可提高电池的容量并改善循环稳定性。作为锂离子动力电池的正极材料已有产业化应用,在新能源汽车领域具有良好的应用前景。由于纯二氧化锰本身的颜色主要是在棕色和黄色之间变化,光调制幅度较小,因此作为电致变色器件的电极材料,通常将其与其它光调制幅度较大的材料进行复合使用。如聚苯胺/二氧化锰杂化电致变色薄膜较纯聚苯胺薄膜在形貌、结构和电致变色性能上有巨大差异,显示出更高的光调制幅度、着色效率和循环稳定性。纳米二氧化锰在乙苯的催化转化和空气污染物的催化消除方面发挥重要作用。纳米二氧化锰能够增大电流响应、降低检出限,使检测的灵敏度大大提高,近年来在生物传感器领域逐渐被大家重视并得到广泛应用,如二氧化锰纳米片辅助荧光偏振生物传感器可有效检测环境水样中Ag+,PtAu-MnO2二元纳米结构修饰的石墨烯纸在非酶葡萄糖检测中表现出良好的传感性能。在结语部分,分析了当前纳米二氧化锰的制备和应用方面存在的问题,指出了纳米二氧化锰在锂离子电池正极材料和电致变色器件中应用的发展方向,并对其未来的发展前景进行了展望。

等级结构锰氧化物的简易合成及其用于锂离子电池负极的研究（英文）

锰氧化物具有高的理论储锂容量同时原料丰富,有望用于高性能锂离子电池的负极材料。本文报道一种室温下的氧化还原沉淀反应合成具有等级球形二氧化锰的方法。该方法简便有效,同时得到的材料具有无定形和晶畴共存的结构特点。以其为前驱物,进一步制备了单晶纳米片组装的花形尖晶石型锰酸钴。该温和的合成方法不同于传统的水热或固相合成方法,能够避免颗粒间因团聚引起的活性表面的损失。所得到的二氧化锰和锰酸锂均具有优异的电化学储锂性能,有望用于锂离子电池和其它储能领域。

A facile fabrication route for binary transition metal oxide-based Janus nanoparticles for cancer theranostic applications

Janus nanoparticles （JNPs） have multiple configurations for molecular imaging, targeting, and therapeutic effects on cancers; these properties have made these particles attractive for biomedical applications. Nonetheless, smart strategies for the controlled synthesis in a liquid phase and exploration of the appropriate applications of JNPs remain a challenge. In this study, a unique liquid-phase method was applied to fabricate Mn3O4-TiO2/ZnO/Fe3O4 multifunctional binary transition metal oxide-based JNPs, using the concept of epitaxial growth and lattice mismatch among synthesized materials. Transmission electron microscopy and scanning transmission electron microscopy results revealed that the created materials are embedded in the form of dimers with good dispersion and homogeneous growth in a nonpolar solvent. Pluronic F-127-coated MnBO4- TiO2 JNPs were utilized as a contrast agent in T1-weighted magnetic resonance imaging （MRI） and in photodynamic therapy （PDT） for cancers in vitro and in vivo. In vivo T1-weighted MRI of the heart, liver, and kidneys in mice after intravenous injection of the nanoparticles revealed high sensitivity and biocompatibility of as-synthesized Mn3O4--TiO2 JNPs. Results of synchrotron X-ray fluorescence microscopy mapping showed the stability of the nanocomposites and efficiency of penetration into the cytoplasm and perinuclear area. Inorganic TiO2 photosensitizers showed promising tumor ablation performance in PDT in vitro and in vivo at low intensity of UV irradiation （5.6 mW.cm-2） because of their ultrasmall size and photodegradable stability. These results reveal that multifunctional Mn3O4-TiO2 JNPs enhance a T1-weighted MRI contrast and have excellent properties for PDT and therefore, may be a novel agent for cancer theranostics.