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《化工进展》2017,(Z1)
钙钛矿型氧化物催化剂(ABO3)具有廉价易得、高热稳定性、催化活性高的优点,在催化一氧化碳(CO)低温脱除领域具有重要的理论研究意义和实际应用价值。本研究中,以聚苯乙烯(PS)微球、碳微球为模板,硝酸镧、硝酸钴、硝酸铁为金属源,柠檬酸为络合剂,通过溶胶-凝胶法制备了多孔LaCoO_3和多孔LaFeO_3催化剂。采用X射线衍射、热重-差热、扫描电镜、透射电镜和氮气吸附-脱附等手段对所得样品进行了系统表征分析。结果表明:所制备的催化剂具有高纯度和高热稳定性。加入11.12g PS微球所制备的多孔LaCoO_3催化剂平均颗粒粒径为13nm,加入0.5g碳微球制备的多孔LaFeO_3催化剂平均粒径为19nm,且具有介孔和微孔分级孔结构。催化性能测试结果表明:在同等条件下对CO转化率达到50%时,多孔LaCoO_3和多孔LaFeO_3使得催化温度分别降低了43℃和32℃;CO完全转化温度则分别降低了90℃和60℃。 相似文献
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(Cudpt)(ClO4)2和K4[Fe(CN)6]反应得到配位聚合物(Cudpt)3[Fe(CN)6](ClO4)2*3H2O(1),在相似条件下用Cu(ClO4)2,dpt和K4[Fe(CN)6]反应得到配位聚合物(Cudpt3[Fe(CN)6](ClO4)2*4H2O(2),解析了它们的晶体结构.这两个化合物有相同的I.R.和UV-Vis谱,但它们的结构却有显著的不同,前者是一维链状结构,后者则是二维网状结构. 相似文献
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用密度泛函理论(DFT)研究了标题化合物的电子结构、电离能和稳定性。研究发现,体系的交错型(D4d)结构是稳定的,而重叠型(D4h)异构体则是过渡态。从垂直电离能的计算可知,Fe、Ru和Os的配合物对分子内的库仑排斥力而言是不稳定的,而Co、Rh和Ir的类似物则是稳定的。此外,计算结果表明,钠能作为抗衡离子来抵消分子内的库仑排斥力,使电子不会自发地离去,因为这样可以产生更稳定的结构,即[P4MP4Na]-,从而可以便于实验操作。另外,金属-配体裂解反应能的计算表明这些夹心型配合物都是热稳定的。 相似文献
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将自然界丰富的氮转化为氨对人类社会发展至关重要。以氮和水为原料的电化学合成氨是极具应用前景的绿色合成过程。采用水热法合成了Ni-, Co-和Zn-MOF-74催化剂,采用XRD、SEM以及XPS等表征了催化剂结构,并在0.1 mol·L-1Na2SO4电解液中研究了它们的电催化合成氨性能。结果表明,在常温常压下,Ni-MOF-74的电催化合成氨性能优于Co-和Zn-MOF-74催化剂,在-0.7 V (vs Ag/Ag Cl)下其氨合成速率和法拉第效率分别高达6.68×10-11mol·s-1·cm-2和23.69%,这归因于Ni-MOF-74不仅颗粒尺寸小且分布均匀,而且具有最多的金属-氧键和最大的电化学比表面。特别是Ni-MOF-74还能有效抑制析氢副反应,从而提高了法拉第效率。 相似文献
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将富锂锰基正极材料Li2MnO3·LiMO2(M=Co,Ni)分为LiMO2和Li2MnO3两部分,基于密度泛函理论第一性原理方法对其分别进行了研究,分析和计算了LiMO2(M=Co,Ni)的结构和性能及Li2MnO3的脱锂过程。结果表明:在LiMO2(M=Co,Ni)和Li2MnO3中锂以离子形式存在,LiNiO2体系的导电性优于LiCoO2体系,Li2MnO3在脱锂过程中锂离子首先从锂层中脱出,之后从过渡金属层进一步脱锂,其中锂脱出造成的电荷变化主要由O的氧化来补偿。 相似文献
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以金属有机框架(ZIF-67、Ni-MOF)为前躯体,在氮气下煅烧合成了类Fenton催化剂Co@C、Ni@C,并对催化剂进行了X射线衍射分析,拉曼测试(Raman),扫描电镜(SEM)表征。研究了Co@C和Ni@C催化剂对染料橙黄Ⅱ的降解能力。实验结果表明,碳包覆不同金属的催化剂对橙黄Ⅱ的降解能力存在着明显的差异。在橙黄Ⅱ浓度为20 mg/L,催化剂浓度为25 mg/L,PMS浓度为0.1 g/L,Co@C比Ni@C催化剂有着优异的降解能力。 相似文献
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Matthew T. Kapelewski Julia Oktawiec Tomče Runčevski Miguel I. Gonzalez Jeffrey R. Long 《Israel journal of chemistry》2018,58(9-10):1138-1143
The separation of Xe and Kr from air is challenging owing both to the very low atmospheric concentrations of these gases and the need for their distillation at cryogenic temperatures. Alternatively, separation processes based on adsorption could provide a less energy-intensive route to the isolation of these gases. Here, we demonstrate that the metal–organic frameworks M2(m-dobdc) (M=Co, Ni; m-dobdc4−=4,6-dioxido-1,3-benzenedicarboxylate) effectively separate Xe and Kr at ambient temperatures based on the different adsorption enthalpies of each gas at the coordinatively-unsaturated M2+ sites in each material. In situ Xe- and Kr-dosed powder X-ray diffraction studies further reveal key differences in the binding of Xe and Kr within the materials. In particular, while both gases adsorb near the framework open metal sites at 200 K, much higher Xe occupancies are observed at these sites relative to Kr, corroborating a stronger interaction of the polarizing M2+ cations with Xe. Further, while krypton is only found located above the open metal sites, two additional adsorption sites are observed for xenon, correlating with the stronger adsorption of Xe over Kr in these materials. These results suggest the possible utility of employing M2(m-dobdc) materials in the adsorptive separation of Xe and Kr. 相似文献
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《Ceramics International》2017,43(2):2089-2094
La0.6Sr0.4M0.1Fe0.9O3-δ (M: Co, Ni and Cu) perovskite nanostructures were synthesized using low frequency ultrasound assisted synthesis technique and effect of substitution of Fe by Co, Ni and Cu on crystal structure and mechanical properties in La0.6Sr0.4FeO3-δ perovskite was studied. The HRTEM and Rietveld refinement analyses revealed the uniform equi-axial shape of the obtained nanostructures with the existence of La0.6Sr0.4M0.1Fe0.9O3−δ with mixed rhombohedral and orthorhombic structures. Substitution by Cu decreases the melting point of La0.6Sr0.4FeO3-δ. The results of mechanical characterizations show that La0.6Sr0.4Co0.1Fe0.9O3−δ and La0.6Sr0.4Ni0.1Fe0.9O3−δ have ferroelastic behavior and comparable elastic moduli, however, substitution by Ni shows higher hardness and lower fracture toughness than Co in B-site doping. 相似文献
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Alumina supported phosphovanodomolybdic acid and alumina supported phosphovanodomolybdic acid‐transition metal ions (M: Fe3+, Co2+, or Ni2+) were prepared by impregnation. The thermal decomposition, in situ at 400°C, of supported catalysts showed the formation of V2O5, P2O5, MoO3 and MoO3, CoMoO4, (Mo0.3V0.7)2O5 phases, on the alumina surface, in the presence of H4PMo11VO40/α‐Al2O3 and H4PMo11VO40? Co/α‐Al2O3, respectively. The catalytic activity of alumina‐supported catalysts was evaluated in the reaction of propane oxidation at 380 and 400°C. The addition of transition metal increases the conversion and changes the reaction products distribution. The reaction conditions (temperature and propane/oxygen ratio) have also modified the behaviour of the studied catalysts. 相似文献
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《Ceramics International》2017,43(6):5032-5040
Nanostructured La-based perovskite oxides − LaMO3 (M=Al, Co, Fe) were synthesized by a new co-precipitation procedure using metal nitrate and carbonate salts as starting materials. X-ray diffraction and energy dispersive X-ray spectroscopic results confirmed the formation of single-phase nanocrystalline perovskite oxides with high purity. Characterizations by scanning/transmission electron microscopy and nitrogen adsorption revealed that LaAlO3 was produced in the form of rectangular porous nanorods exhibiting much larger surface area and porosity compared with densely aggregated LaCoO3 particles and loosely clustered LaFeO3 nanoparticles with cracked-egg morphologies. The materials were characterized for gas sensing towards ethanol at 200–350 °C. From gas-sensing results, the LaAlO3 sensor displayed n-type gas-sensing behaviors with considerably higher ethanol response than p-type LaFeO3 and LaCoO3 sensors, respectively. In particular, the LaAlO3 sensor exhibited a high response of 16.45–1000 ppm ethanol and excellent ethanol selectivity against NO2, SO2, CO and H2 at 350 °C. The superior gas-sensing performances could be attributed to the effective receptor function, transducer function and utility factor of LaAlO3 nanorod structures prepared by the co-precipitation method. 相似文献
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《Ceramics International》2023,49(16):26530-26539
Perovskite-like rhombohedral distorted solid solutions of BiFe1-х(M1/2Ti1/2)хO3 (M = Co, Ni, Zn, x = 0–0.11) were obtained by solid-phase synthesis. An indicator of the solid solution formation is the change of unit cells parameters, that corresponds to the ionic radii of mixed cations (M1/2Ti1/2)3+ (M = Co, Ni, Zn. Solid solutions of BiFe1-х(M1/2Ti1/2)хO3 (M = Co, Ni), in contrast to BiFe1-x(Zn1/2Ti1/2)xO3 demonstrate ferromagnetic hysteresis pels at room temperature. The x growth in the range from 0.01 to 0.11 for the BiFe1-х(M1/2Ti1/2)хO3 system leads to, the saturation magnetization MS and the remanent magnetization MR increase from ∼0.1 and ∼2.4⋅10−3 emu/g to ∼0.4 and ∼0.038 emu/g respectively. In the same time the coercive force Hc decreases from ∼120 to ∼80 Oe. For the BiFe1-х(Co1/2Ti1/2)хO3 system, a noticeably higher magnetic properties with a more complex dependence on x are observed. The maximum parameter values are observed at x = 0.04–0.05: MS = 0.83 and MR = 0.24 emu/g, Hc = 1.8 kOe. It is suggested that the detected anomalies of Co-containing solid solutions behavior are related to the one-ionic magnetocrystalline anisotropy of Co2+ cations. The BiFe1-х(M1/2Ti1/2)хO3 (M = Co, Ni) samples demonstrate piezoelectric constant d33 up to 7 pC/N. Due to the set of properties the materials obtained can be classified as high-temperature multiferroics. 相似文献
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采用低温固相法与常规液相法合成系列磷酸铵复盐NH4MPO4.H2O(M=Mn,Fe,Co,Ni,Cu),用XRD,FT-IR和SEM对产物进行表征,比较两种合成工艺及产物的颗粒形貌和大小。结果表明,除铜盐为斜方晶系外,其余都为正交晶系。与常规液相法相比,低温固相法不需要使用溶剂,能在低温短时间内合成磷酸铵复盐类化合物,但是需要晶化才能得到良好结晶体,合成的条件较为苛刻,容易有副反应发生,所得产品是片状结构,厚度为纳米尺寸的二维纳米材料,液相反应得到的产物颗粒是层状结构的微米级产品。 相似文献