MnOx／Al2O、MnOx／BaO—Al2O3催化剂的制备、表征及其对甲烷低温燃烧的催化活性

改变锰的负载最及前驱体,制备了MnOx/Al2O、MnOx/BaO-Al2O3系列催化剂;采用X-射线衍射（XRD）、程序升温还原（TPR）对催化剂进行表征,并考察了BaO的加入对CH4低温燃烧催化活性的影响。结果表明,用醋酸锰作前驱体与用硝酸锰制备的催化剂相比,其活性组分分散性好、氧中心活性高,催化CH4低温燃烧的活性高。在Al2O3载体中掺入BaO,催化剂的氧中心数目的没有明显变化,但氧中心活性有所下降,因而降低了对CH4低湿燃烧的催化活性。     

采用积雪草树叶提取物生物合成二氧化镁纳米粒子负载的铜纳米颗粒用于高效催化还原有机染料和芳香硝基化合物（英文）

本文设计了一个经济、绿色的新型方法,采用积雪草树叶提取物作为自然的还原剂,在不使用稳定剂或表面活性剂的情况下合成了MnO_2纳米粒子负载的Cu纳米颗粒(CuNPs).该合成过程环境友好,且避免使用有毒的还原剂.树叶提取物中的酚羟基将溶液中的Cu~(2+)还原为Cu NPs,后者再稳定在MnO_2 NPs表面.采用X射线衍射、透射电镜、场发射扫描电镜、能量散射谱和红外光谱对所得Cu/MnO_2纳米复合物进行了表征.结果表明,该材料可用作高活性、高效可重复使用的多相催化剂,用于室温水溶液NaBH_4存在下刚果红、罗丹明B和亚甲基蓝,以及硝基化合物,如2,4二硝基苯肼和4-硝基苯酚的催化还原.Cu/MnO_2纳米复合物的高稳定性可使其被分离出来,重复使用数次而活性无明显下降.     

合成路径对超级电容器用二氧化锰性质的影响

研究了不同合成路径对二氧化锰结构及电化学性能的影响. 路径1为将0.15 mol/L醋酸锰溶液加入到0.1 mol/L高锰酸钾溶液中; 路径2中, 物料的加料方式与路径1相反. X射线衍射和扫描电镜测试表明合成的产物均为无定型α-MnO2, 晶粒尺寸为200～300 nm. 氮吸附曲线测试结果表明: 路径1所得的二氧化锰具有较大的比表面积(329 m2/g), 其孔径分布比较均一, 孔径6～12 nm, 孔体积较小(0.45 cm3/g); 路径2所得的二氧化锰比表面积较小(298 m2/g), 具有从微孔到大孔的连续分布孔, 平均孔径11.4 nm, 孔体积较大(0.66 cm3/g). 交流阻抗和循环伏安电化学测试结果显示: 路径2所得样品具有较大的法拉第阻抗, 在较低扫描速度下(2 mV•s－1), 其比电容(203 F•g－1)比路径1所得MnO2高(189 F•g－1), 路径1所得二氧化锰的比电容随扫描速度变化的趋势较小. 恒流充放电测试显示路径1合成的二氧化锰具有较好的功率特性. 在2 A•g－1的电流密度下, 其比容量为0.1 A•g－1电流密度下的96.3%, 而路径1的样品的容量保持率为92.5%. 造成上述结果差异的原因是由于不同合成路径导致二氧化锰存在不同的孔结构特征所致.     

Formation of Nanostructured MnO/Co/Solid–Electrolyte Interphase Ternary Composites as a Durable Anode Material for Lithium‐Ion Batteries

Nanoporous MnO frameworks with highly dispersed Co nanoparticles were produced from MnCO₃ precursors prepared in a gel matrix. The MnO frameworks that contain 20 mol % Co exhibited excellent cycle performance as an anode material for Li‐ion batteries. The solid–electrolyte interphase (SEI) formed in the frameworks through the electrochemical reaction mediates the active materials, such as MnO, Mn, and Li₂O, during the conversion reaction in the charge–discharge cycle. The Co nanoparticles and SEI provide the electron and Li‐ion conductive networks, respectively. The ternary nanocomposites of the MnO framework, metallic Co nanoparticles, and embedded SEI are categorized as durable anode materials for Li‐ion batteries.     

Oxygen evolution from BF3/MnO4-

MnO(4)(-) is activated by BF(3) to undergo intramolecular coupling of two oxo ligands to generate O(2). DFT calculations suggest that there should be a spin intercrossing between the singlet and triplet potential energy surfaces on going from the active intermediate [MnO(2)(OBF(3))(2)](-) to the O···O coupling transition state.     

Catalysis Conversion Methane into C2 Hydrocarbons via Electric Field Enhanced Plasma

In this paper the effect of catalyst and carrier in electric field enhanced plasma on methane conversion into C2 hydrocarbons was investigated. Methane coupling reaction was studied in the system of continuous flow reactor on Ni, MoO3, MnO2 catalysts and different ZSM-5 carriers. The per pass conversion of methane can be as high as 22%, the selectivity of ethylene can be as high as 23.8%, of acetylene 60.8%, of ethane 5.4% and of total C2 hydrocarbons was more than 90%. ZSM-5-25 was the better carrier and MnO2 was the better active component. The efficiency of energy was as high as 7.81%.     

NO对LaMnO3与La0.8K0.2MnO3催化氧化碳烟活性影响

采用柠檬酸络合法制备LaMnO3和La0.8K0.2MnO3钙钛矿催化剂,运用程序升温氧化(TPO)考察在不同反应气氛下催化燃烧碳烟的活性,并通过XRD,O2-TPD,NO-TPD,XPS以及NO预处理后O2-TPD等技术对催化剂进行表征和分析。结果表明,NO的存在促进了碳烟的催化氧化,但是对LaMnO3和La0.8K0.2MnO3氧化碳烟的促进效果不同。这与催化剂表面氧空位和活性氧物种有密切联系。     

石英晶体微天平分析不同介孔二氧化锰材料的电化学性能

以碳酸锰(MnCO3)为前体,空气氛围下采用不同温度(300℃、350℃、400℃)煅烧, 制备了3种介孔二氧化锰(MnO2)材料,分别与粘结剂混合喷涂至石英晶片作为电极,利用石英晶体微天平(QCM)监测了3种材料在0.1 mol/L Na2SO4溶液中随循环伏安过程的电化学性能变化.分析结果表明,3种材料在首圈循环中都呈现出显著的质量增加,发生了不可逆反应过程; 300℃煅烧制备的MnO2材料具备更好的电化学稳定性和容量保持能力.将300℃, 350℃和400℃煅烧的MnO2各自作为正极与活性炭负极组成超级电容器, 进行充放电测试,首圈均有35％～40％的容量损失; 三者稳定循环时放电容量分别为15.9, 12.9和11.7 mA h/g.QCM的分析与充放电测试结果相一致,表明QCM可用于比较不同介孔二氧化锰材料的电化学性能.     

Amorphization and recrystallization study of lithium insertion into manganese dioxide

Various polymorphs of MnO(2) are widely used as electrode materials in Li/MnO(2) batteries. Electrolytic manganese dioxide (EMD) is the most electrochemically active form of MnO(2) and is very difficult to characterize. Their structural details are still largely unknown owing to the poor quality of X-ray diffraction (XRD) patterns obtained from most MnO(2) samples. Simulated amorphisation and crystallization technique was used to derive microstructural models for Li-MnO(2) which included most microstructural details that one would expect to find in the real material. Specifically, pyrolusite-MnO(2), comprising about 25,000 atoms, was amorphised (strain-induced) under molecular dynamics (MD) and different concentrations of lithium ions were inserted. Each system was then crystallized under MD simulation. The resulting models conformed to the pyrolusite polymorph, with microstructural features including: extensive micro-twinning and more general grain-boundaries, stacking faults, dislocations and isolated point defects and defect clusters. Molecular graphical images, showing the atom positions for the microstructural features together with simulated XRD patterns they give rise to, are presented and compared with measured XRD. The calculated XRD are in accord with experiment thus validating the structural models.     

MnO2/C复合材料的电化学电容特性研究

应用乙炔黑直接还原高锰酸钾制备MnO2/C复合材料.样品结构及性能由XRD和SEM表征.研究了MnO2/C电极(正极)在不同电解液中的法拉第"准电容行为",及其循环伏安、交流阻抗与恒电流充放电等性能.实验表明,MnO2/C复合材料具有良好的电化学电容特性.在1 mol/L的KOH电解液中和电流密度为5 mA/cm2下,MnO2/C复合材料的比电容量可达258 F/g,并表现出良好的循环性能.     

超声波电氧化合成纳米MnO_2及其在制备甘油醛中的应用

于阳离子隔膜的电解槽中,以MnO2/Mn2+电对作催化氧化的媒介,在超声波高频振荡下,电生成的MnO2颗粒以几十nm至几μm尺寸分散在溶液中.随后将甘油电化学氧化为甘油醛,该MnO2/Mn2+电对催化活性的选择性高,电流效率可达97.4%.     

质子交换膜燃料电池MnO2-Pt/C复合催化剂阴极的富氧作用

质子交换膜燃料电池空气电极阴极催化剂的富氧作用是提高其性能的关键.应用化学氧化法制备MnO2-Pt/C复合催化剂,研究MnO2的富氧作用,应用CV、CP、TEM等方法表征该催化剂,并组装成单电池测试其性能.     

纳米MnO锂离子电池负极材料的制备与性能

以高锰酸钾和抗坏血酸合成的MnC₂O₄·2H₂O为前驱体, 通过固相烧结制备了纳米MnO材料. 分别采用X射线衍射(XRD)、扫描电子显微镜(SEM)和恒电流充放电技术考察了其晶相结构、颗粒形貌和电化学性能.分析结果表明, 该纳米MnO具有面心立方的岩盐结构, 结晶度良好. 其颗粒是由粒径为50-100 nm的一次颗粒结合而成的二次颗粒, 大小约为400-600 nm. 当充放电电流密度为46.3 mA·g^-1时, 纳米MnO的首次库仑效率可达68.9%, 可逆比容量为679.7 mAh·g^-1. 在141.1 mA·g^-1的电流密度下循环50圈后, 比容量由584.5mAh·g^-1降至581.5 mAh·g^-1, 容量保持率高达99.5%, 表现出优异的循环性能. 此外, 当电流密度增加到494.7 mA·g^-1 (~2C)时, 其比容量依然可达290 mAh·g^-1, 表现出较好的倍率性能和快速充放电能力. 因此, 纳米MnO具有比容量高、循环稳定、倍率性能好和安全环保等优点,是一种非常有前景的锂离子电池负极材料.     

Generating MnO2 nanoparticles using simulated amorphization and recrystallization

Models of MnO2 nanoparticles, with full atomistic detail, have been generated using a simulated amorphization and recrystallization strategy. In particular, a 25,000-atom "cube" of MnO2 was amorphized (tension-induced) under molecular dynamics (MD). Long-duration MD, applied to this system, results in the sudden evolution of a small crystalline region of pyrolusite-structured MnO2, which acts as a nucleating "seed" and facilitates the recrystallization of all the surrounding (amorphous) MnO2. The resulting MnO2 nanoparticle is about 8 nm in diameter, conforms to the pyrolusite structure (isostructural with rutile TiO2, comprising 1 x 1 octahedra) is heavily twinned and comprises a wealth of isolated and clustered point defects such as cation vacancies. In addition, we suggest the presence of ramsdellite (2 x 1 octahedra) intergrowths. Molecular graphical snapshots of the crystallization process are presented.     

纳米电极材料的制备及其电化学性质研究(Ⅲ)——微乳液中通氧气制备MnO_2及其性能

本文采用锰盐微乳液中通氧气法成功制备了超细粉末ＭｎＯ２,对所得样品进行了化学分析,ＸＲＤ,ＴＥＭ测试,证明为γ ＭｎＯ２,平均粒径在纳米级范围内．再经恒电流放电,循环伏安,分形维数,交流阻抗等测试,发现在适当制备条件下所得纳米ＭｎＯ２具有良好的放电性能,并对此作了初步的理论探讨     

SbOx+SnO2中间层对Ti/MnO2电极性能的影响

采用热分解方法制备了含SbO_x+SnO₂中间层的钛基二氧化锰电极. 在0.5 mol·L^-1 H₂SO₄溶液中对添加和没有添加SbO_x+SnO₂中间层的二氧化锰阳极进行了加速电解试验. 采用极化曲线和循环伏安曲线测量电极的析氯反应. 用循环伏安曲线和电化学阻抗谱来分析电极电解过程中内部结构和表面的变化. 结果表明, 二氧化锰阳极钝化失效的主要原因是绝缘的TiO₂层的生成和变厚. 引入中间层可以降低钛基体和活性涂层间的电阻, 并且在电解过程中, 可以显著延缓接触电阻的升高, 从而可以显著提高其寿命.     

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.     

聚多巴胺还原高锰酸钾制备二氧化锰阵列纳米管

以通过水热法在石英玻璃片表面合成的ZnO纳米棒为模板,在其表面生成聚多巴胺薄膜,然后与KMnO4反应,制备了MnO_2阵列纳米管。经表征发现,制备的MnO_2纳米管形态良好,在基底表面的附着力强;所制备的MnO_2为非晶型。由于ZnO模板易合成、易去除、形态好,且聚多巴胺薄膜的生成方法也很简便易行,使得该制备MnO_2纳米管阵列的方法具有简便、快捷、适用性广等的特性,对MnO_2新形态纳米结构的构建具有一定的启示作用。     

垃圾催化燃烧的热重分析研究

采用热重分析,结合机理分析的方法,探讨了不同催化剂对垃圾焚烧过程中着火性能和燃尽性能的影响。结果表明,催化剂对垃圾着火性能的提高主要是催化剂促进了垃圾中挥发性有机物的释放,使着火点提前;催化剂对垃圾燃尽性能的提高,主要作用机理是催化剂充当氧的载体,促进氧转移。提出了表征着火性能和燃尽性能的两个物理参数,并根据两个参数对催化剂进行排序和比较。催化剂影响着火性能大小进行排序：K2CO3> MnO2 > Na2CO3> CuO > MgO > TiO2 > Al2O3 > Fe2O3 > BaCO3> CaO;催化剂影响垃圾燃尽性能大小排序：Na2CO3>MgO> MnO2> K2CO3> BaCO3> CaO> Al2O3> CuO> Fe2O3> TiO2。     

超级电容器电极材料MnO_2纳米棒的制备及其电化学性能(英文)

以洋葱碳为还原剂,KMnO4为氧化剂,稀硫酸溶液为溶剂,采用水热法一步制备MnO2纳米棒.利用X射线衍射仪和透射电子显微镜分析了MnO2纳米棒的物相、结构、形貌;将MnO2纳米棒作为电极材料组装了超级电容器,采用电池测试系统测定了超级电容器的电化学性能.结果表明,所得到的产物为α-MnO2,其直径为5~10nm,长度为50~100nm;以MnO2纳米棒作为电极材料组装的超级电容器具有较高的比容量和稳定性,有望在超级电容器的研究和应用中得到推广.