TPR investigations on the reducibility of Cu supported on Al2O3, zeolite Y and SAPO-5

Reducibility of Cu supported on Al₂O₃, zeolite Y and silicoaluminophosphate SAPO-5 has been investigated in dependence on the Cu content using a method combining conventional temperature programmed reduction (TPR) by hydrogen with reoxidation in N₂O followed by a second the so-called surface-TPR (s-TPR). The method enables discrimination and a quantitative estimation of the Cu oxidation states +2, +1 and 0. The quantitative results show that the initial oxidation state of Cu after calcination in air at 400 °C, independent on the nature of the support, is predominantly +2. Cu²⁺ supported on Al₂O₃ is quantitatively reduced by hydrogen to metallic Cu⁰. Comparing the TPR of the samples calcined in air and that of samples additionally pre-treated in argon reveals that in zeolite Y and SAPO-5 Cu²⁺ cations are stabilized as weakly and strongly forms. In both systems, strongly stabilized Cu²⁺ ions are not auto-reduced by pre-treatment in argon at 650 °C, but are reduced in hydrogen to form Cu⁺. The weakly stabilized Cu²⁺ ions, in contrast, may be auto-reduced by pre-treatment in argon at 650 °C forming Cu⁺ but are reduced in hydrogen to metallic Cu⁰.     

MnO2纳米线支撑中空十二面体CoNi2S4的制备及其电化学性能

采用简单的室温搅拌法和一步硫化法制备了 MnO₂纳米线支撑中空十二面体 CoNi₂S₄ (MnO₂/CoNi₂S₄)电极材料。超长MnO₂纳米线为电子转移提供了直接路径,而且其较大的长径比有利于形成自支撑的三维导电网络结构;中空多孔的CoNi₂S₄提供了更丰富的活性位点,同时缓解了充放电过程中的体积变化。得益于以上优势,MnO₂/CoNi₂S₄在1 A·g^-1时具有1 531.1 F·g^-1的比电容,在 10 A·g^-1时具有 86.9% 的电容保持率。利用 MnO₂/CoNi₂S₄作为正极、活性炭(AC)为负极组装的 MnO₂/CoNi₂S₄||AC器件实现了高能量密度(800 W·kg^-1时40 Wh·kg^-1)和优异的循环稳定性(5 000次循环后保持64.8%)。     

ESR study of SO2 on MnO2-alumina

SO ₃ ^– radicals are formed during the reaction between SO₂ and MnO₂-alumina, which suggests that SO ₃ ^– take part in the reduction of Mn⁴⁺ to Mn²⁺.

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SO₂ MnO₂/Al₂O₃ SO ₃ ^– , , SO ₃ ^– Mn⁴⁺ Mn²⁺.

     

Sulfation of CuO,Fe2O3, MnO2, and NiO with (NH4)2SO4

An attempt has been made to calculate the free energy values for possible reactions utilising the available thermodynamic data in order to study the sulfation of CuO, Fe₂O₃, MnO₂ and NiO with (NH₄SO₄, and further trials have been made to determine the exact reaction through differential thermal analysis. There is no real correlation between the theoretical value of ΔH° and that calculated from the DTA peak, which may be due to some uncertainty in the thermodynamic values and the possibility of some side reactions.     

Oxidizing supported reagents, III. Oxidation of alcohols by new supported K2Cr2O7 reagents

Several new supported K₂Cr₂O₇ reagents are used in the oxidation of secondary alcohols. The influence of the number of active sites and the nature of solid support on the yield is discussed. The influence of the structure of alcohol on the yield of ketone is analyzed.

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K₂Cr₂O₇ . . .

     

Photocatalytic activity of different morphology BiPO4 supported on zeolite

Highly efficient sheet-like Bi PO₄/zeolite and ball-flower-like Bi PO₄/zeolite had been successfully synthesized by a standard hydrothermal method.The addition of assistant reagent in the hydrothermal system is promising to obtain special morphology.The assistant reagent（EDTA） acts as a growth modifier of crystal.The possible formation mechanisms of sheet-like Bi PO₄/zeolite and ball-flower-like Bi PO₄/zeolite were schematically discussed.A detailed study of sheet-like Bi PO₄/zeolite and ball-flower-like Bi PO₄/zeolite impacted on the photodecoloration methylene blue（MB） solution showed that the composite had a highly reusable and stable property for long-run photocatalytic application.     

Synthesis and characterization of MnO2 colloids

This work addresses the issue of radiation chemical synthesis of MnO₂ nanoparticles and also illustrates the ease of formation of nanorods and sheets by adroit manipulation of experimental conditions. The radiation chemical yield (G-value) for reduction of Mn (VII) by the hydrated electron was found to be 0.27 μmol J⁻¹ and 0.17 μmol J⁻¹ respectively, when tert. butanol and isopropanol were used as scavengers in nitrogen-saturated solutions. The colloids formed upon irradiation of air-saturated solution and N₂-purged solution with tert. butanol as scavenger were found to be most stable. Irradiation of air-saturated solution containing 4×10⁻⁴ M KMnO₄ at a dose of 1692 Gy resulted in the formation of nanorods of the dimension 100–150 nm and nanospheres in the range 10–20 nm. Irradiation of N₂-purged solution containing tert. butanol as scavenger for OH-produced reticulated structure of nanorods with length varying from 50 to 100 nm at a dose of 1692 Gy. Elemental analysis was performed using scanning electron microscope on MnO₂ formed by reduction and oxidation and the purity was found to be 98% of elemental Mn content.     

CoTiO3纳米粉体的合成及其对MnO2电极材料的改性作用

采用溶胶-凝胶法制得钙钛矿型CoTiO₃纳米粉体，借助XRD、TEM以及循环伏安测试对其性质进行了表征。不同量的所制样品用于MnO₂电极的物理掺杂，进行了深度恒流放电、循环伏安和充放电测试。结果表明在40%KOH电解质溶液中，样品掺杂量为5%时改性效果较好。纳米CoTiO₃参与了电极反应，抑制了电化学惰性物质Mn₃O₄的生成，从而有效地改善MnO₂的放电性能，放电容量较I.C     

原位聚合MnO_2/PoPD@PPS复合滤料及其NH_3-SCR脱硝性能研究

在聚苯硫醚(PPS)滤料表面包覆一层二氧化锰/聚邻苯二胺(PoPD)复合物。利用π-π共轭效应,将邻苯二胺(OPD)单体均匀吸附在PPS纤维表面,然后通过高锰酸钾溶液使邻苯二胺氧化聚合,在纤维表面原位生成聚邻苯二胺包覆层,同时高锰酸钾被还原成MnO_2催化剂,插入到聚邻苯二胺基体中。通过原位聚合生成的MnO_2/PoPD复合物与PPS滤料间有很强的黏结性,使得催化剂和滤料能牢固地结合在一起。该复合滤料制备方法简单,实验条件温和,对滤料本身性能没有损伤,通过FESEM、XPS、XRD、FT-IR、脱硝活性测试等对其结构和性能进行了研究。脱硝测试结果表明,KMnO4/PPS质量比为1∶1时,复合滤料在80-180℃下脱硝率可达36%-94%,10 h的催化剂稳定性测试中,其脱硝率在160℃下仍保持在88%;Mn 2p的XPS谱图证实复合滤料上催化剂为MnO_2;复合滤料的XRD谱图表明MnO_2为非晶结构;从FESEM照片可以看出,MnO_2催化剂在PPS滤料上分散均匀。     

First Principles Study of H-insertion in MnO2

We present an extensive First Principles study on proton intercalation in the pyrolusite and ramsdellite forms of MnO₂. It is shown that protons are always covalently bonded to an oxygen atom in MnO₂. In ramsdellite, the proton prefers the pyramidal oxygen to the planar coordinated oxygen as that site is farther away from the Mn cations. In both pyrolusite and manganite, the octahedral sites are unstable, but the two local minima on each side of the octahedron are connected by a barrier of only about 25 meV, so that protons may rapidly exchange between these sites. Proton diffusion in pyrolusite occurs by hopping along the 1×1 open tunnels with an activation barrier that increases from about 575 meV at the beginning of discharge to about 1eV at high H concentration. Diffusion in ramsdellite takes place along the 2×1 open tunnels and occurs with much lower activation energy (respectively, 200 and 400 meV, at low and high H concentrations). Introduction of twinning defects has a large adverse effect on the proton diffusivity. Results indicate that direct H-H interactions are not that significant compared to oxygen-mediated-interactions. Experimental and calculated ramsdellite discharge curves deviate significantly at early stages of the reduction process. The calculations on defected structures indicate that a significant source of this discrepancy may be due to presence of proton-compensated Mn vacancies in real MnO₂, which create local sites with higher discharge potential. The calculations suggest that the ordered phase, observed in experiments at mid-reduction (groutellite, MnOOH_0.5), is due to the lattice remaining coherent during intercalation.     

含氧空位的氟掺杂二氧化锰助力稳定锌离子电池

将无机盐NH₄F加入到MnO₂的前驱体溶液中,通过高效、简单的一步水热法制备了具有氧缺陷的F掺杂α-MnO₂纳米棒(记为F-MnO₂)。氧空位和F掺杂对提高F-MnO₂的导电性、促进离子扩散、提高倍率性能起着至关重要的作用。另外,由于F掺杂,形成了F—Mn键,这可以有效地抑制放电产物中Mn³⁺的Jahn-Teller畸变,从而提高结构的稳定性。得益于这些协同效应,组装的Zn||F-MnO₂全电池在0.5 A·g^-1下,首圈放电比容量高达274 mAh·g^-1,且具有较长的循环寿命和优异的倍率性能。同时,通过循环伏安(CV)和恒流充放电(GCD)曲线证明了F-MnO₂的储能机制为H⁺和Zn²⁺的共嵌入/脱出过程。     

碳螺旋纤维/MnO2复合材料的电化学性能

利用电泳沉积法(EPD)制备碳螺旋纤维基MnO_2@CMC复合材料,采用电子扫描电镜、拉曼光谱(Raman)、X射线光电子能谱(XPS)对其形貌和结构进行表征并测试其电容性能,结果显示:当电位差扫描速率为5 m V·s-1时,充放电容量较高,可达115F·g-1,在0.2 A·g-1的扫描电流下,循环200圈后电容量为96.7 F·g-1,为起始电容量的89.5%,表现出良好的电容保持率和循环稳定性。     

MnO2 /聚苯胺复合材料的制备和性能

以δ-MnO₂为前驱体,通过酸处理后引入苯胺并聚合,得到了MnO₂ /聚苯胺复合材料。经XRD分析表明,在本研究条件下,经酸处理后的δ-MnO₂晶型由δ型转变为α型,而在随后的苯胺引入及其聚合步骤中MnO₂晶型均不再改变。以200 mA·g^-1的电流进行恒电流充放电性能测试,结果显示,MnO₂ /聚苯胺复合材料的充放电容量达到160.2 mA·g^-1,与     

Nonenzymatic electrochemical glucose sensor based on MnO2/MWNTs nanocomposite

In this communication, an amperometric glucose biosensor based on MnO₂/MWNTs electrode was reported. MnO₂ was homogeneously coated on vertically aligned MWNTs by electrodeposition. The MnO₂/MWNTs electrode displayed high electrocatalytic activity towards the oxidation of glucose in alkaline solution, showing about 0.30 V negative shift in peak potential with oxidation starting at ca. −0.20 V (vs. 3 M KCl–Ag/AgCl) as compared with bare MWNTs electrode. At an applied potential of +0.30 V, the MnO₂/MWNTs electrode gives a linear dependence (R = 0.995) in the glucose concentration up to 28 mM with a sensitivity of 33.19 μA mM⁻¹. Meanwhile, the MnO₂/MWNTs electrode is also highly resistant toward poisoning by chloride ions. In addition, interference from the oxidation of common interfering species such as ascorbic acid, dopamine, and uric acid is effectively avoided. The MnO₂/MWNTs electrode allows highly sensitive, low-potential, stable, and fast amperometric sensing of glucose, which is promising for the development of nonenzymatic glucose sensor.     

电感耦合等离子体原子发射光谱法测定烧结增效剂中三氧化二硼和二氧化锰

提出了电感耦合等离子体原子发射光谱法测定烧结增效剂中主成分三氧化二硼和二氧化锰含量的方法。用盐酸-硝酸混合溶液溶解样品,选择波长257.610,249.773 nm两条谱线分别作为测定硼和锰的分析线,采用背景校正来扣除干扰。方法用于烧结增效剂样品分析,测定结果与化学法测定值相一致。     

Steam reforming of methanol over group VIII metals supported on SiO2, Al2O3 and ZrO2

Thermal activation of brown coal for production of porous carbon materials in a set-up with fluidized oxidation catalyst has been studied.     

Strong H2 chemisorption on Al2O3 or SiO2 supported group VIII metals

Following hydrogen treatments at high temperature a decrease in hydrogen chemisorption at room temperature is observed in almost all group VIII elements supported on SiO₂ or Al₂O₃. The effect is attributed to self inhibition by strongly chemisorbed hydrogen on the metals.

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VIII , SiO₂ Al₂O₃. .

     

MnO2上氧气第一个电子转移步骤的从头计算研究

采用裸露簇和嵌入簇模型, 对β-MnO₂ (001), (110), (111)三个晶面以及O₂在(110)晶面的单址吸附模式(Pauling和Griffths模式), 进行从头计算. 从β-MnO₂ (001), (110), (111)三个晶面的电子结构差异以及O₂在(110)晶面吸附的吸附能、几何结构、集居数以及净电荷数分析得到: (001), (110), (111)三个晶面中(110)晶面的催化活性最高, 其活性顺序为(110)＞(111)＞(001). 氧气在(110)晶面的吸附, Pauling和Griffths两种吸附模式均存在, 属于化学吸附中的离子吸附. 氧气与MnO₂固体间发生了单电子转移, 氧气得到电子被还原成O₂^-, 转移电子属于整个体系, 具有离域性.     

Ascorbic acid sensor based on ion-sensitive field-effect transistor modified with MnO2 nanoparticles

An ascorbic acid (AA) sensor based on an ion-sensitive field-effect transistor (ISFET) was prepared by modifying the sensitive area of the transducer with MnO₂ nanoparticles. An additional Nafion membrane coated on top of the sensor was used to immobilize the MnO₂ nanoparticles and restrict the amount of ascorbic acid entering the membrane. The reaction of the MnO₂ nanoparticles with ascorbic acid produced a local pH change, which was correlated with the ascorbic acid concentration and could be monitored by the ISFET. The linear range of the ascorbic acid sensor was 0.02-1.27 mM, and the detection limit was 0.01 mM. The effects of buffer concentration, pH, and ionic strength on the sensor performance were also examined. In addition, the sensor has good stability and reproducibility, and the construction and renewal of the sensor are simple and inexpensive.