Understanding the catalysis of chromium trioxide added magnesium hydride for hydrogen storage and Li ion battery applications

This study explores how the chemical interaction between magnesium hydride(MgH_(2))and the additive CrO_(3) influences the hydrogen/lithium storage characteristics of MgH_(2).We have observed that a 5 wt.%CrO_(3) additive reduces the dehydrogenation activation energy of MgH_(2) by 68 kJ/mol and lowers the required dehydrogenation temperature by 80℃.CrO_(3) added MgH_(2) was also tested as an anode in an Li ion battery,and it is possible to deliver over 90%of the total theoretical capacity(2038 mAh/g).Evidence for improved reversibility in the battery reaction is found only after the incorporation of additives with MgH_(2).In depth characterization study by X-ray diffraction(XRD)technique provides convincing evidence that the CrO_(3) additive interacts with MgH_(2) and produces Cr/MgO byproducts.Gibbs free energy analyses confirm the thermodynamic feasibility of conversion from MgH_(2)/CrO_(3) to MgO/Cr,which is well supported by the identification of Cr(0)in the powder by X ray photoelectron spectroscopy(XPS)technique.Through high resolution transmission electron microscopy(HRTEM)and energy dispersive spectroscopy(EDS)we found evidence for the presence of 5 nm size Cr nanocrystals on the surface of MgO rock salt nanoparticles.There is also convincing ground to consider that MgO rock salt accommodates Cr in the lattice.These observations support the argument that creation of active metal–metal dissolved rock salt oxide interface may be vital for improving the reactivity of MgH_(2),both for the improved storage of hydrogen and lithium.

TiO_2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NO_x with NH_3

Binary metal oxide（MnOx-A/TiO2）catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide（TiO2）,where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order：Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order：Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h？ 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared（FTIR）spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.

Comparison Study on the Microstructure of Nanocrystalline TiO_2 in Different Ti-Si Binary Oxides

Three different Ti-Si oxide structuares, silica supported titania, silica coated titania and intimately mixed silicatitania, containing 10%-40% SiO2, were made by sol-gel process. The variations of microstructure parameters of nanocrystalline （nc） TiO2-anatase in the three kirds of binary oxides, including in-plane spacing d, cell constants （ao, co）, cell volume V, cell axial ratio co/ao and crystal grain size, were comparatively investigated by high resolution transmission electron microscopy （HRTEM） and X-ray diffraction （XRD）. It is found that the microstructure parameters vary remarkably with increasing SiO2 content and annealing temperature. Different structured Ti-Si binary oxides lead to different variation tendencies of microstructure parameters. The more SiO2 the binary oxide contains, the more lattice defects of nc TiO2-anatase appear; diffusion or migration of Si cations could be an important influential factor in the variations of microstructure. The grain size of nc TiO2 in the three kinds of binary oxides not only depends on SiO2 content and annealing temperature but also on the degree of lattice microstrain and distortion of nc TiO2-anatase. Both grain size and phase transformation of nc TiO2-anatase are effectively inhibited with increasing SiO2 content.

CO_2 methanation over TiO_2–Al_2O_3 binary oxides supported Ru catalysts

TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.

THE NEW MODEL FOR CALCULATION OF STANDARD ENTROPIES OF SOLID COMPOUNDS Ⅲ CALCULATION FOR STANDARD ENTROPIES OF SOLID BINARY OXIDES

This paper establishes a new model for calculation of the standard entropies of solid binary oxides as follows: S_(29)=27.07×Φ_1+1.120×Φ_2+n_1×k×Φ, -22.19 e.u (R=0.9960) We have invesigated 103 binary oxides. and found good agreemenl between estimated and experimental entropies.

Screening of MgO- and CeO_2-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C_(2+) Hydrocarbons

The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.

Phase Stability, Kinetic Diagrams and Diffusion Path in High Temperature Oxidation of Binary Solid-Solution Alloys

The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams, which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.

Influence of Binary Oxidant (FeCl₃:APS) Ratio on the Spectroscopic and Microscopic Properties of Poly(2,5-Dimethoxyaniline)

Poly(2,5-dimethoxyaniline) (PDMA) has been synthesized by chemical oxidative polymerization technique using varying ratio (wt/wt) of binary oxidants;ferric chloride (FeCl3) and ammonium persulfate (APS). Fourier transform infrared (FT-IR) and ultraviolet-visible (Uv-vis) spectroscopic investigations provide the evidence of the presence of both benzenoid and quinoid ring units. The thermal analysis and structural characterization data suggests that the oxidant ratio greatly controls the molecular ordering in PDMA. Surface morphology shows the existence of both amorphous and crystalline domains wherein the crystalline domain size depends on the oxidant ratio. The dc conductivity (σdc) of PDMA is also a function of binary oxidant ratio and at FeCl3:APS (50:50), it increases by two orders of magnitude. Films of PDMA synthesized using FeCl3:APS (50:50) binary oxidant exhibits a decrease in the surface current on exposure to ammonia gas.

Synthesis,characterization and fluorescence of N,N'-BIS (6-metyl-2-pyridinecarboxylamide-N-oxide)-1,2-ethane and corresponding rare earth (Ⅲ) complexes

A new ligand, N,N-BIS (6-metyl-2-pyridinecarboxylamide-N-oxide)-1,2-ethane (L) and six lanthanide(Ⅲ) complexes (RE=La, Sm, Eu, Tb, Gd, Yb) were synthesized and characterized in detail. The results indicated that the composition of the binary complexes was determined as [REL(H2O)(NO3)2]NO3·nH2O (n=0-2), and the Eu3+ complex had bright red fluorescence in solid state. Three complexes of Eu3+, Tb3+, and Gd3+ with 6-methylpicolinic acid N-oxide (L’) were also synthesized. The relative intensity of sensitized luminescence for Eu3+ increased in the following order: L>L’. The phosphorescence spectra of the Gd3+ complexes at 77 K were measured. The energies of excited triplet state for the ligands were 20704 cm-1 (L) and 20408 cm-1 (L’). The facts that the ligands sensitized Eu3+ strongly and the order of the emission intensity for Eu3+ complexes were explained by ΔE(T-5D). This meant that the triplet energy level of the ligand was the main factor to influence RE3+ luminescence.

Synthesis, Characterization and Properties of N,N′-Bis(6-methyl-2-pyridine-N-oxide)-1,3-Propane and Europium and Terbium Complexes

A new ligand, N,N′-Bis(6-methyl-2-pyridine-N-oxide)-1,3-propane (L), and some binary lanthanide complexes (Ln=Eu^(3+), Tb^(3+)) were synthesized and characterized in detail. The composition of the binary complexes was determined as LnL(NO_3)_3. They are 1∶1 electrolytes in DMF. The complexes have strong characteristic line fluorescence emission spectra, and it is also found that TbL(NO_3)_3 complex has stronger luminescence intensity than EuL(NO_3)_3 in solid state and in methanol.

二元磁性S_(2)O_(8)^(2-)/Fe_(3)O_(4)-ZrO_(2)固体超强酸催化合成乙酸乙酯工艺研究

以无水氯化锆、过硫酸铵、硫酸亚铁、硝酸铁为原料,采用共沉淀-浸渍法制备了二元磁性S_(2)O_(8)^(2-)/Fe_(3)O_(4)-ZrO_(2)固体酸催化剂,利用IR、XRD、BET、NH_(3)-TPD对二元磁性固体酸进行表征,并用于乙酸乙酯的合成反应。实验结果表明:催化剂制备条件为Fe_(3)O_(4)的添加量35%,过硫酸铵的浸渍浓度0.5 mol/L;适宜的酯化条件为醇酸摩尔比3∶1,酯化时间2 h,固体超强酸的用量0.5 g。以S_(2)O_(8)^(2-)/Fe_(3)O_(4)-ZrO_(2)为催化剂乙酸乙酯酯化率90.25%,重复4次后,乙酸乙酯的酯化率可达62.5%。

铁锰二元氧化物改性粉煤灰对地下水中砷的吸附特性

在我国内陆盆地和河流三角洲广泛分布着高砷地下水,吸附法作为一种简单而高效的除砷方法得到广泛的应用,但大多数吸附材料对As(Ⅲ)的吸附能力弱于As(Ⅴ),因此开发具有氧化和吸附耦合作用的高效吸附剂具有积极意义。采用共沉淀法制备铁锰二元氧化物改性粉煤灰(FMFA),探究其对As(Ⅲ)/As(Ⅴ)的吸附性能及吸附机理;通过批实验探究FMFA对溶液中As(Ⅲ)/As(Ⅴ)的吸附性能,采用XRD、SEM、BET等表征分析其表面形貌和结构,利用XPS和FT-IR分析吸附前后FMFA表面元素和官能团变化。结果表明:铁、锰氧化物均以不定形相负载于粉煤灰表面,极大地提高了FMFA的比表面积(可达166.77 m^(2)/g),为As(Ⅲ)/As(Ⅴ)的吸附提供了更多的活性位点;FMFA在中性条件下对As(Ⅲ)和As(Ⅴ)的理论最大吸附容量分别为68.19 mg/g和24.42 mg/g,As(Ⅲ)/As(Ⅴ)的吸附等温线模型均符合Freundlich模型,As(Ⅴ)的吸附过程遵循准二级动力学模型,As(Ⅲ)的吸附过程更符合Elovich模型;在溶液初始pH=5~9范围内FMFA的稳定性较好,初始pH>9的碱性环境不利于As(Ⅴ)/As(Ⅲ)的吸附;水中常见共存含氧阴离子对As(Ⅲ)/As(Ⅴ)竞争吸附影响大小的顺序为PO_(4)^(3-)>HCO_(3)^(-)>SO_(4)^(2-);FMFA可有效去除地下水样品中的砷,且不会造成铁、锰二次污染,同时具有良好的回收再生能力;在FMFA吸附As(Ⅲ)的过程中二氧化锰主要起氧化作用,铁氧化物起吸附作用,砷通过与FMFA表面金属活性羟基配体交换形成内球络合物而被吸附。本文成功制备了可高效去除地下水中As(Ⅲ)/As(Ⅴ)的绿色经济的新型吸附剂,对保障居民饮用水安全具有重要意义。

两种形貌的高储电性能ZnCo_(2)O_(4)电极材料

由于ZnCo_(2)O_(4)具有合成方法简单、成本低廉等优点,成为超级电容器领域的一种重要电极材料.通过水热、退火两步处理,制备了两种不同形貌的ZnCo_(2)O_(4)材料,并在三电极体系中测试其超级电容器性能.结果表明,花状形貌的ZnCo_(2)O_(4)纳米片微球比纳米片状ZnCo_(2)O_(4)的性能更好.电流密度1 A·g^(-1)时,ZnCo_(2)O_(4)纳米片微球电极的比电容高达3 005.0 F·g^(-1);电流密度20 A·g^(-1)时,比电容仍能保持2150.0F·g^(-1),电容保持率为71.5%.循环充/放电10000次后,电容保持率仍达到93.8%.该ZnCo_(2)O_(4)纳米片微球电极材料在超级电容器电极领域具有良好的应用前景.

Catalytic degradation of benzene over non-thermal plasma coupled Co-Ni binary metal oxide nanosheet catalysts

Non-thermal plasma(NTP)has been demonstrated as one of the promising technologies that can degrade volatile organic compounds(VOCs)under ambient condition.However,one of the key challenges of VOCs degradation in NTP is its relatively low mineralization rate,which needs to be addressed by introducing catalysts.Therefore,the design and optimization of catalysts have become the focus of NTP coupling catalysis research.In thiswork,a series of two-dimensional nanosheet Co-Ni metal oxides were synthesized by microwave method and investigated for the catalytic oxidation of benzene in an NTP-catalysis coupling system.Among them,Co_(2)Ni_(1)O_(x)achieves 60%carbon dioxide(CO_(2))selectivity(SCO_(2))when the benzene removal efficiency(REbenzene)reaches more than 99%,which is a significant enhancement compared with the CO_(2)selectivity obtained without any catalysts(38%)under the same input power.More intriguingly,this SCO_(2)is also significantly higher than that of single metal oxides,NiO or Co_(3)O_(4),which is only around 40%.Such improved performance of this binary metal oxide catalyst is uniquely attributed to the synergistic effects of Co and Ni in Co_(2)Ni_(1)O_(x)catalyst.The introduction of Co_(2)Ni_(1)O_(x)was found to promote the generation of acrolein significantly,one of the key intermediates found in NTP alone system reported previously,suggest the benzene ring open reaction is promoted.Compared with monometallic oxides NiO and Co_(3)O_(4),Co_(2)Ni_(1)O_(x)also shows higher active oxygen proportion,better oxygenmobility,and stronger low-temperature redox capability.The above factors result in the improved catalytic performance of Co_(2)Ni_(1)O_(x)in the NTP coupling removal of benzene.

Structural and Performance Regulation of Binary Transition-Metal Oxides Toward Supercapacitors:Advances and Prospects

Binary transition-metal oxides(BTMOs)are attractive candidates for advanced supercapacitors(SCs)because of their ultrahigh specific capacitance,tunable structures as well as morphologies,and low cost.To promote the practical application of BTMOs,their structure–performance relationship and developmental bottleneck should be further understood.In this review,the crystal structures and corresponding electrochemical properties of typical BTMOs in various aqueous electrolytes are briefly introduced.Some ingenious methods for improved electric conductivity,mainly including building integrated electrodes and composites,introducing oxygen vacancy,and element doping are carefully discussed.Some practicable ideas for boosting cycle stability through avoiding or alleviating agglomeration,volume change,and dissolution are provided in detail.Finally,the existing problems and challenges for structural and performance regulation of BTMOs are generalized.This review will support valuable information for building better SCs using BTMOs.

Novel synthesis of SiO_x/C composite as high-capacity lithium-ion battery anode from silica-carbon binary xerogel

Micro/nanostructured SiOx/C composite was firstly synthesized by carbothermal reduction of silica-carbon binary xerogel.The homogeneous dispersion feature of the two components in binary xerogel contributes to effectively carbothermally reduce the O/Si atomic ratio,enhancing the electrochemical activity of the SiOx component.The micron-sized SiOx/C spheres are composed of many near-spherical nanoparticles.The synthesized SiOx/C exhibits a stable and high reversible capacity of 830 m A·h·g^-1 for 100 cycles,and excellent rate-capability.The homogeneous dispersion structure of phases,the micro/nanostructure and the high electrochemical activity of SiOx component combinedly contribute the excellent electrochemical performance.

Removal of tetracycline from water by Fe-Mn binary oxide

Significant concerns have been raised over the presence of antibiotics including tetracyclines in aquatic environments.A series of FeMn binary oxide with different Fe：Mn molar ratios was synthesized by a simultaneous oxidation and coprecipitation process for TC removal.Results showed that Fe-Mn binary oxide had higher removal efficiency than that of hydrous iron oxide and hydrous manganese oxide,and that the oxide with a Fe：Mn molar ratio of 5：1 was the best in removal than other molar ratios.The tetracycline removal was highly pH dependent.The removal of tetracycline decreased with the increase of initial concentration,but the absolute removal quantity was more at high concentration.The presence of cations and anions such as Ca2＋,Mg2＋,CO32-and SO42-had no significant effect on the tetracycline removal in our experimental conditions,while SiO32-and PO43-had hindered the adsorption of tetracycline.The mechanism investigation found that tetracycline removal was mainly achieved by the replacement of surface hydroxyl groups by the tetracycline species and formation of surface complexes at the water/oxide interface.This primary study suggests that Fe-Mn binary oxide with a proper Fe：Mn molar ratio will be a very promising material for the removal of tetracycline from aqueous solutions.

Mesoporous nickel-iron binary oxide nanorods for efficient electrocatalytic water oxidation

The design and fabrication of low-cost, high-effidency, and stable oxygen-evolving catalysts are essential for promoting the overall efficiency of water electrolysis. In this study, mesoporous Ni1-xFexOy （0 〈 x 〈 1, 1 〈y 〈 1.5） nanorods were synthesized by the facile thermal decomposition of Ni-Fe-based coordination polymers. These polymers passed their nanorod-like morphology to oxides, which served as active catalysts for oxygen evolution reaction （OER）. Increasing the Fe-doping amount to 33 at.% decreased the particle size and charge-transfer resistance and increased the surface area, resulting in a reduced overpotential （-302 mV） at 10 mA/cm^2 and a reduced Tafel slope （-42 mV/dec）, which were accompanied by a far improved OER activity compared with those of commercial RuO2 and IrO2 electrocatalysts. At Fe-doping concentrations higher than 33 at.%, the trend of the electrocatalytic parameters started to reverse. The shift in the dopant concentration of Fe was further reflected in the structural transformation from a NiO （〈33 at.% Fe） rock-salt structure to a biphasic NiO/NiFe204 （33 at.% Fe） heterostructure, a NiFe204 （66 at.% Fe） spinel structure, and eventually to α-fe203 （100 at.% Fe）. The efficient water-oxidation activity is ascribed to the highly mesoporous one-dimensional nanostructure, large surface area, and optimal amounts of the dopant Fe. The merits of abundance in the Earth, scalable synthesis, and highly efficient electrocatalytic activity make mesoporous Ni-Fe binary oxides promising oxygen-evolving catalysts for water splitting.

Comparing the adsorption behaviors of Cd, Cu and Pb from water onto Fe-Mn binary oxide, MnO2 and FeOOH

The adsorption potential of FMBO, FeOOH, MnO2 for the removal of Cd^2＋, Cu^2＋ and Pb^2＋ in aqueous systems was investigated in this study. Comparing to FMBO and FeOOH, MnO2 offered a much higher removal capacity towards the three metal ions. The maximal adsorption capacity of MnO2 for Cd^2＋, Cu^2＋ and Pb^2＋ were 1.23, 2.25 and 2.60 mmol· g^-1, respectively. And that for FMBO were 0.37, 1.13, and 1.18mmol·g^-1 and for FeOOH were 0.11, 0.86 and 0.48 mmol·g^-1, respectively. The adsorption behaviors of the three metal ions on the three adsorbents were all significantly affected by pH values and heavy metal removal efficiency increased with pH increased. The Langmuir and Freundlieh adsorption models were used to describe the adsorption equilibrium of the three metal ions onto the three adsorbents. Results showed that the adsorption equilibrium data fitted well to Langmuir isotherm and this indicated that adsorption of metal ions occurred on the three metal oxides adsorbents limited to the formation of a monolayer. More negative charged of MnOa surface than that of FMBO and FeOOH could be ascribed by lower pHiep of MnO2 than that of FMBO and FeOOH and this could contribute to more binding sites on MnO2 surface than that of FMBO and FeOOH. The higher metal ions uptake by MnO2 than FMBO and FeOOH could be well explained by the surface charge mechanism.

Adsorption Kinetic Properties of As(Ⅲ)on Synthetic Nano Fe-Mn Binary Oxides

The adsorptive removal of arsenic by synthetically-prepared nano Fe-Mn binary oxides（FM） was investigated. A novel method using potassium permanganate and ferric chloride as raw materials was used to synthesise FM. The molar ratio of Fe and Mn in the synthetic Fe-Mn binary oxides was 4 ： 3. The FM-1 and FM-2（prepared at different activation temperatures） having high specific surface areas（358.87 and 128.58 m^2/g, respectively） were amorphous and of nano particle types. The amount of arsenic adsorbed on FM-1 was higher than that adsorbed on FM-2 particles. After adsorption by FM-1, residual arsenic concentration decreased to less than 10 μg/L. The adsorption kinetics data were analyzed using different kinetic models including pseudo first-order model, pseudo second-order model, Elovich model and intraparticle diffusion model. Pseudo second-order kinetic model was the most appropriate model to describe the adsorption kinetics. The adsorption percentage of As（Ⅲ） increased in the p H range of 2–3 while it decreased with the increase of pH（ 3〈pH〈10）. The effects of coexisting anions on As（Ⅲ） removal using FM-1 and FM-2 were also studied and the order of the effects is as follows： NO_3^-, Cl-, F-〈SO_4^（2-）, HCO_3-〈H_2PO_4^-, indicating that H_2PO_4^- is the major competitor with As（Ⅲ） for adsorptive sites on the surface of the adsorbents. The higher adsorption capacity of FM-1 makes it potentially attractive adsorbent for the removal of As（Ⅲ） from groundwater.