聚多巴胺包覆的钙钛矿修饰电极用于电化学检测水中铜、汞和铅离子

通过水热法合成具有钙钛矿结构的LaCo0.21Ni1.59O3,将聚多巴胺(PDA)包覆在LaCo0.21Ni1.59O3表面,得到PDA@LaCo0.21 Ni1.59 O3复合材料.利用钙钛矿优异的电催化性能和PDA丰富的胺基基团,将复合材料修饰在玻碳电极(GCE)表面,构建了一种新型电化学传感平台(PDA@LaC...     

钙钛矿结构B位掺杂化合物LaCO1-xFexO3的光催化活性研究

用柠檬酸溶胶-凝胶法制备了钙钛矿型LaCo1-xFexO3系列化合物，使用XRD、XPS、红外和紫外等手段对其进行了表征和测定，并测定了其对活性艳红水溶性染料脱色的光催化活性．实验结果表明在B位掺杂Fea 后使LaCoO3光催化活性明显提高，当x=0．05时，即LaCo1-xFexO3的光催化活性最佳。     

LaCo0.9Cu0.1O3的蔗糖溶胶-凝胶法合成及二甲苯催化氧化性能研究

蔗糖溶胶 凝胶法合成了稀土钙钛矿型复合氧化物LaCo0 .9Cu0 .1 O3,并对其进行了XRD ,BET ,TPR表征和二甲苯催化氧化性能测试 ,并与柠檬酸溶胶 凝胶法作了比较。结果表明 ,蔗糖作为络合剂成胶和干胶容易 ,粒径较小 ,具有进一步降低LaCo0 .9Cu0 .1 O3形成温度的作用 ,以蔗糖作为络合剂在 70 0℃所制备的催化剂LaCo0 .9Cu0 .1 O3低温活性较好。     

Sr掺杂钙钛矿体系中高活性氧析出反应机制（英文）

析氧反应(oxygen evolutionreaction OER)是电催化分解水、二氧化碳还原、金属-空气电池以及燃料电池等能源转化及存储技术的关键过程,因此被广泛关注和研究.OER过程涉及四个电子转移,是动力学迟滞过程,具有较大的过电位,此外OER催化反应的同时也可能改变电极表面状态,故其机理的研究十分困难.设计和开发高效OER催化剂材料是提高电解水效率的关键.最近的研究发现反应后催化剂表面会发生重构,进而形成无定形层,该无定形层被认为会改善催化活性.我们的前期研究也发现了表面不饱和配位无定形层的存在,但对于重构机制尚没有明确的解释.本文在上述研究基础上,利用熔盐法合成了一系列具有多孔结构的不同Sr含量的LaCo0.8Fe0.2O3-δ钙钛矿材料,通过电化学装置测试其催化活性,并采用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电镜(HRTEM)、比表面积测试(BET)和软硬X射线吸收谱技术等表征手段对其进行了深入探索.XRD测试结果表明,Sr掺杂LaCo0.8Fe0.2O3-δ钙钛矿材料的主峰随着Sr含量增加向低角度偏移,这是由于Sr的离子半径较La的大.SEM和BET测试结果表明,不同Sr含量样品均表现出多孔的钙钛矿结构,并具有相似的比表面积,说明Sr含量变化不影响催化剂的形貌和比表面积.利用硬X射线吸收谱对体相Co和Fe元素的价态进行了研究,发现随着Sr含量的增加,Co和Fe离子的价态没有明显变化.类似地,利用软X射线吸收谱对表面层Co和Fe价态进行的研究发现,Co和Fe均表现出+3价,但在氧元素的K边吸收谱上观察到明显的氧空穴存在.电化学测试结果表明,催化剂的活性随Sr含量增加而增大.总之,随着Sr的掺杂,催化剂形貌及活性元素价态均无明显变化,但样品的电化学性能却发生了明显改善,这意味着尚有其它因素影响催化剂活性.利用HRTEM对OER反应前后的样品进行了形貌分析,发现在OER反应后Sr掺杂的催化剂表面出现了明显的无定形层,而无Sr掺杂的样品反应前后几乎未观察到表面形貌的变化.由此我们推断,Sr掺杂可诱导催化剂表面出现无定形层,进而提高OER反应活性.因此,在LaCo0.8Fe0.2O3-δ钙钛矿材料体系中,Sr掺杂是影响OER催化剂表面重构和制约催化活性的关键.     

La1-x-yCaxKyMnO3的可控合成及表征

采用水热合成方法,通过调控反应物中Ca2+与La3+的摩尔比可控合成了钙钛矿结构La1-x-yCaxKyMnO3(0.05≤x≤0.49;0.05≤y≤0.21)系列样品,利用X射线衍射仪、扫描电子显微镜、等离子光谱仪及磁性测量系统对样品的结构、形貌、成分组成和磁学性质进行了研究.结果表明,该水热反应过程为歧化反应,K+离子的引入导致了样品中双铁磁相的出现.     

Ce掺杂对La1-xCexCoO3催化剂的结构和催化氧化性能的影响

采用非晶态配合物的方法合成了La1-xCexCoO3(x=0、0.05、0.1、0.2、0.3)催化剂, 并采用X射线衍射(XRD)、透射电镜(TEM)和比表面测定仪(BET)等手段对催化剂的微观结构进行了研究. 揭示了Ce掺杂对催化剂的钙钛矿结构, CO催化氧化以及催化氧化发光性能的影响规律. 结果表明, 在Ce4+掺杂部分取代La3+后, 催化剂形成了镧不足的La1-xCeyφx-yCoO3(φ是A位离子空位)钙钛矿相以及CeO2和Co3O4物相. 与LaCoO3催化剂相比, x=0.1催化剂的CO催化氧化活性最高(T100%=290 ℃). La1-xCexCoO3催化剂对CO催化氧化发光的响应与其催化活性密切相关.     

钐掺杂对钛酸钡锶陶瓷结构和介电性能的影响

采用溶胶-凝胶法制备了系列Sm掺杂的Ba(0.8-3x/2)SmxSr0.2TiO3(x=0,0.001,0.003,0.006,0.008 and 0.010)粉体及陶瓷。利用X射线粉末衍射、扫描电子显微镜和精密阻抗分析表征了样品的结构和性质。X射线衍射结果表明Ba(0.8-3x/2)SmxSr0.2TiO3粉体在800℃预烧2 h后为单一的钙钛矿结构;通过对陶瓷微观形貌研究发现,Sm掺杂可以明显地抑制陶瓷晶粒生长,随着Sm掺杂量的增加,晶粒尺寸由40μm减小到2μm;居里温度随着Sm掺杂量的增加而线性降低,移动速率为10℃/mol%,室温下介电常数呈现先增加后减小的趋势,并在x=0.006时达到最大值7800。     

La0.75Sr0.25Mn1-xNixO3＋δ材料的制备及其催化甲烷部分氧化性能

采用柠檬酸络合法制备了La0.75Sr0.25Mn1-xNixO3+δ(x=0,0.4,0.5和0.6)系列样品,考察了其对甲烷部分氧化的催化性能,并采用X射线衍射、H2程序升温还原、O2程序升温脱附和程序升温氧化等测试手段表征样品.结果表明,当x=0,0.4和0.5时,样品均形成稳定的钙钛矿结构:当x=0.6时样品同时存在钙钛矿和菱形六面体尖晶石结构.当x=0.5时样品存在4种可还原物种,同时具有高的表面氧特别是高的晶格氧含量,对甲烷部分氧化有利,这表明La0.75Sr0.25Mn0.5Ni0.5O3+δ具有良好的抗积炭性能.催化性能测试结果表明,当x=0.5时,样品具有良好的甲烷中温转化率,最高的CO和H2选择性,以及在700℃下最好的反应稳定性和抗积炭能力.     

ABO3型钙钛矿结构的可见光光催化剂LaCo0.5Ti0.5O3的设计与合成

采用溶胶-凝胶法在较低温度条件下设计合成了新型的具有ABO3型钙钛矿结构的三元金属复合氧化物LaCo0.5Ti0.5O3. 通过TG-DTA, XRD, XPS, UV-Vis DRS等测试技术和可见光光催化活性测试对其进行了表征. 结果表明, 与LaCoO3和La2Ti2O7相比, LaCo0.5Ti0.5O3样品表现出相对较高的可见光光催化活性, 并且合成温度较低. 这是由于原料中的Co2+和Ti4+离子通过电荷补偿作用使产物B位的两种金属均以+3价氧化态分布所致.     

La_(1-x)Ba_xCo_(0.8)Ni_(0.2)O_3复合氧化物的制备及其对CO催化燃烧性能

采用溶胶-冷冻干燥法制备了La1-xBaxCo0.8Ni0.2O3(x=0~0.4)催化剂粉体。用X射线衍射(XRD)、比表面测定仪(BET)和扫描电子显微镜(SEM)等分析手段对催化剂的结构和形貌进行了表征,并考察了催化剂的最佳焙烧温度和催化活性。研究表明,催化剂的最佳焙烧温度为600℃。掺杂Ba2+后,催化剂以钙钛矿相和BaCO3相共存,不能形成单一的钙钛矿型结构。催化活性测试表明,当x=0.2时,催化剂对CO的催化活性最高(T90%=126℃)。     

Nature of catalytic activities of CoO nanocrystals in thermal decomposition of ammonium perchlorate

This work addresses the chemical nature of the catalytic activity of X-ray "pure" CoO nanocrystals. All samples were prepared by a solvothermal reaction route. X-ray diffraction indicates the formation of CoO in a cubic rock-salt structure, while infrared spectra and magnetic measurements demonstrate the coexistence of CoO and Co 3O 4. Therefore, X-ray "pure" CoO nanocrystals are a unique composite structure with a CoO core surrounded by an extremely thin Co 3O 4 surface layer, which is likely a consequence of the surface passivation of CoO nanocrystals from the air oxidation at room temperature. The CoO core shows a particle size of 22 or 280 nm, depending on the types of the precursors used. This composite nanostructure was initiated as a catalytic additive to promote the thermal decomposition of ammonium perchlorate (AP). Our preliminary investigations indicate that the maximum decomposition temperature of AP is significantly reduced in the presence of CoO/Co 3O 4 composite nanocrystals and that the maximum decomposition peak shifts toward lower temperatures as the loading amount of the composite nanocrystals increases. These findings are different from the literature reports when using many nanoscale oxide additives. Finally, the decomposition heat for the low-temperature decomposition stages of AP was calculated and correlated to the chemical nature of the CoO/Co 3O 4 composite nanostructures.     

Single step synthesis of high-purity CoO nanocrystals

Both octahedral and slice-shaped cubic cobalt monoxide (CoO) nanocrystals with narrow size distributions have been successfully synthesized by a simple solvothermal route. It was found that conditions of the solvothermal treatment showed obvious effects on the formation and purity of the as-synthesized CoO nanocrystals, only when cobalt acetate was used as the cobalt source and when temperature reached 190 degrees C could CoO be produced; also, freeze-drying was necessary for obtaining pure CoO. Size of the CoO nanocrystals varied from 30 to 130 nm. Morphology of the products could be controlled by simply changing the type of surfactant in solvent, and the octahedral CoO nanocrystals showed rounded turns. Purity of the products was detected by intensive X-ray photoelectron spectroscopy (XPS) investigation and Fourier transform infrared spectroscopy (FTIR) combined with differential scanning calorimetry/thermal gravity (DSC/TG). The results indicated an absence of unexpected trivalence cobalt series on surface of the samples, thanks to the protection of the surface by trace amount of carbonate ions, adsorbed hydroxylation, and surfactant with a maximum thickness of 2 nm, which were proved by high-resolution transmission electron microscopy (HRTEM). The as-synthesized CoO nanoparticles were added into positive electrode of Ni/MH batteries, and discharge/charge cycling tests were performed under different rates from 0.1C to 5.0C. The results indicated that the specific capacities of batteries with addition of 5% octahedral or slice CoO nanocrystals at 0.1C were 393.3 and 318.1 mAh/g, respectively, which were higher than that without CoO (269.2mAh/g). Specific capacity of battery with addition of 5% octahedral CoO nanocrystals was 40% higher than that without CoO at 5.0C. Octahedral CoO nanocrystals show better electrochemical activity than slice CoO and indicate interesting potential in the field of electrochemical application.     

Photodegradation of 2-nitrophenol catalyzed by CoO, CoS and CoO/CoS nanoparticles

The nanoparticles of CoO, CoS and CoO/CoS composite are synthesized using precipitation method. The X-ray diffraction, UV–Vis absorption spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy and FT-IR spectroscopy are used to characterize the prepared nanoparticles. The EDX analysis shows the formation of CoO_0.67S_0.33 composite. The XRD pattern indicates the hexagonal structure for nanocomposite. The formation of Co–O and Co–S bonds is confirmed by FT-IR spectra. The band-gap energies of 2.97, 3.06 and 2.91 eV are obtained from UV–Vis spectra of CoO, CoS and CoO/CoS nanoparticles, respectively. The results of photodegradation of 2-nitrophenol show that the photoreactivity order of nanocatalysts is CoO/CoS > CoO > CoS. The pseudo first-order kinetic rate constants of 6.4 × 10^?3, 4.3 × 10^?3 and 12.2 × 10^?3 min^?1 are obtained for CoO, CoS and CoO/CoS nanoparticles, respectively, at photodegradation reaction conditions of pH 10, 30 mg/L of 2-NP and 1.3 g/L of the catalyst. The proposed nanocomposite shows an acceptable reusability and stability against photocorrosion in four-cycle photodegradation experiments.     

CoO/SiO2-Al2O3催化剂上苯胺和1,6-己二醇气相高效合成1-苯基氮杂环庚烷

研究了CoO/SiO2-Al2O3催化剂上苯胺和1,6-己二醇气相催化合成1-苯基氮杂环庚烷的反应,并采用N2吸附-脱附、X射线衍射、H2程序升温还原和NH3程序升温脱附技术对催化剂进行表征.结果表明,CoO/SiO2-Al2O3催化剂表现出较高的活性和选择性.当CoO担载量为0.3mmol/g时,催化剂前体在700℃...     

Structure of the monoclinic-form misfit-layer compound, (Ca0.85OH)2alpha CoO2 (alpha approximately 0.57822)

The incommensurate modulated crystal structure of the new misfit-layer calcium cobalt oxide (Ca0.85OH)2alphaCoO2 was investigated using a superspace-group formalism with synchrotron X-ray diffraction data. The compound is a kind of composite crystal that consists of two interpenetrating subsystems, [CoO2]infinity layers containing triangular lattices formed by edge-sharing CoO6 octahedra, separated from each other by [2Ca0.85OH]infinity double-layered rock-salt-type slabs. Both the subsystems are monoclinic lattices with the unit cell parameters, a1 = 2.8180(4) A, b = 4.8938(6) A, c = 8.810(1) A, alpha0 = 95.75(3) degrees , and alpha(=|q|=a1/a2) = 0.57822(8), viz., a2 = 4.8736 A, with Z = 2. A possible superspace group is C2/m(alpha10)s0-C21/m(alpha(-1)10) for the respective subsystems. The atomic positions deviate from the average positions of the fundamental structure due to the incommensurable periodic interaction between the subsystems. A significant structural modulation was found in the [2Ca0.85OH] subsystem, whereas the modulation in the [CoO2] subsystem is less than in [2Ca0.85OH], due to the tight bonding of the close-packed CoO6 octahedra. The degree of modulation in the CoO2 layers, i.e., the potential modulation, is almost the same as those of other compounds of the misfit-layer cobalt oxides. Flattened CoO6 octahedra indicate hole doping into the CoO2 layers. The [2Ca0.85OH] blocks act as the charge reservoir layers, and the defect Ca ions are presumably the source of the holes.     

Fabrication of CoO nanorods via thermal decomposition of CoC2O4 precursor

Cobalt oxide (CoO) nanorods were synthesized by annealing CoC₂O₄ precursor. The nanorods were identified by Transmission electron microscopy (TEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and other methods. The results showed that the nanorods are composed of cubic CoO with diameter of 10–80 nm, and lengths ranging from 1 to 3 μm. The mechanism of formation of CoO nanorods was also discussed.     

Reinvestigation of the OP4-(Li/Na)CoO2-layered system and first evidence of the (Li/Na/Na)CoO2 phase with OPP9 oxygen stacking

The composition and synthesis conditions of the (Li/Na)CoO(2) phase with an ordered 1:1 Li/Na stacking alternating with CoO(2) slabs were determined from a careful study of the P2-Na(～0.7)CoO(2)-O3-LiCoO(2) system. An in situ X-ray diffraction (XRD) thermal study emphasizes the metastable character of this phase that can be stabilized only by very fast quenching. Its composition, (Li(0.42)Na(0.37))CoO(2), is significantly different from the ideally expected one, (Li(0.50)Na(0.35))CoO(2), and its structure, confirmed by Rietveld refinement of the XRD pattern, presents an ideal alternate ordering of lithium, cobalt, and sodium layers within OP4-type oxygen packing. The presence of vacancies in both alkali-ion layers was confirmed by electrochemical intercalation of lithium and sodium. For the first time, a new type of layered oxide exhibiting OPP9-type oxygen packing was evidenced. Between the CoO(2) slabs, alkali ions are intercalated in the following order: Li(octa)-Na(prism)-Na(prism). This material crystallizes in the R3m space group with a(hex) = 2.828 ? and c(hex) = 46.85 ? cell parameters.     

LaCo(1-x)Ni(x)O(3) with Improved Electrical Conductivity

To determine the applicability of LaCo(1-x)Ni(x)O(3) in a conductive material for electrical wiring, the dependence of the electronic transport property on the Ni content is investigated via Hall effect measurements, Rietveld analyses, and band-structure calculations. Ni doping (50 mol %) into the Co sites realizes a high electrical conductivity of 1.9 × 10(3) S/cm, which is an unexpectedly high value for a LaCo(1-x)Ni(x)O(3) system, at room temperature due to the high carrier concentration of 2.2 × 10(22) cm(-3) and the small effective mass of 0.1 m(e). In addition, the high electrical conductivity is maintained from room temperature to 900 °C; that is, the temperature coefficient of the conductivity is smaller than that of standard metals. Thus, the results indicate that LaCo(0.5)Ni(0.5)O(3) is suitable as a conductive material for electrical wiring at high temperatures in air.     

Wurtzite-to-rocksalt structural transformation in nanocrystalline CoO

Hexagonal CoO nanocrystals are coarsened under hydrothermal conditions to investigate the effect of particle size on phase transformation and stability property. Structural stability and phase transformation of the hexagonal CoO phase have been investigated by X-ray powder diffraction with Rietveld refinement, transmission electron microscopy, X-ray absorption fine structure, and differential scanning calorimeter. It is found that the hexagonal CoO phase is a metastable phase, which increases its grain size from 50 to 250 nm for refluxing times from 1 to 6 h at 200 degrees C. After 12 h, cubic-structured CoO grains with an average grain size of 20 nm are observed, which spread around big hexagonal CoO grains. After about 24 h, only the cubic CoO phase with an average grain size of 25 nm is detected. The onset temperature of hexagonal-to-cubic phase transformation in CoO is estimated to be 378 degrees C by DSC, using a heating rate of 20 deg/min. The results obtained indicate that the hexagonal-to-cubic phase transformation in nanocrystalline CoO is by nucleation and growth mechanism, starting from the surface to the center of the hexagonal grains.     

LaCo1/3Sb5/3O6—A New Oxide Catalyst for CO Oxidation

Doklady Chemistry - A procedure for the synthesis of the LaCo1/3Sb5/3O6 layered oxide with a rosiaite structure has been developed. The method is based on the hydrothermal treatment of...