Study on the adsorption of lanthanum ion imprinted on SBA-15/Y

The lanthanum ion imprinted polymer (La-IIP/SBA-15/Y) was successfully synthesized by the surface ion imprinting method. Using La-IIP/SBA-15/Y as the adsorbent to adsorb lanthanum ions, the overall empirical conditions were optimized, and the best exploratory conditions were finally found. The pH of the solution was 2; the adsorption equilibrium was reached in 60 min and the saturated adsorption capacity was 562.95 mg/g La-IIP/SBA-15/Y adsorbed gadolinium ions in the study of its adsorption process and found that it conforms to the Langmuir isotherm adsorption model, and the adsorption reaction is a spontaneous reaction, and it also conforms to the quasi-second-order kinetic model. The selectivity of the adsorbent was explored experimentally, and the results showed that La-IIP/SBA-15/Y has good selectivity, and experimental elution and regeneration performance. The best elution effect is 2 mol/L hydrochloric acid. La-IIP/SBA-15/Y has good stability and can be reused.     

X射线荧光光谱法测定锡矿石中锡

本文采用向样品中加入硼酸来降低基体效应,加入氧化镧来稳定样品总质量吸收系数,建立固体粉末压片制样-X射线荧光光谱法测定锡矿石中锡含量的方法。通过将标准物质按一定比例混合配制和选取部分自制标样来补充标准物质样品,以解决锡矿石标准物质样品缺乏的问题。实验优化了稀释比,确定了以最佳稀释比为m（矿物质样品）:m（硼酸）：m（氧化镧）=1.0:2.0:0.5。在最优的实验条件下,Sn的荧光强度（kcps）与Sn浓度CSn呈良好的线性关系,R2=0.9989。方法中锡元素的最低检出限为0.005 %,测定范围在0.015 %-4.47 %之间。样品的混合均匀性实验表明各元素测定结果的相对标准偏差（RSD,n=6）在1.0 %-2.64 %之间。对3个不同含量段的物质进行测定来验证方法的准确度和精密度,准确度分别为0.0082-0.0367,均小于0.04,精密度分别为0.39 %-1.18 %,均小于8.0 %,准确度和精密度均符合地质样品分析规范要求。测定值均在误差范围内,各组分测定结果的相对标准偏差（RSD,n=11）在1.20 %以下。粉末压片-X射线荧光光谱法测定锡矿石中锡含量具有分析范围广、分析时间短、重现性好、精度高且操作简单等特点。能应用于地质、环境、材料等领域。     

Role of rhodium doping into lanthanum cobalt oxide (LaCoO3) perovskite and the induced bifunctional activity of oxygen evolution and reduction reactions in alkaline medium

Transition metal oxides, especially perovskites, have been considered effective electrocatalysts for the oxygen evolution (OER) and oxygen reduction (ORR) reactions in an alkaline solution. Here, a series of lanthanum cobalt rhodium oxide perovskites with the chemical formula LaCo_1-xRh_xO₃ (LCRO, 0.1 ≤ x ≤ 0.70) were prepared through the approach of solid-phase synthesis and their bifunctional electrocatalytic activity was assessed for both the OER and ORR. The crystallinity, morphology, surface, and electrocatalytic features of the LCRO were significantly correlated with the rhodium content. The LaCo_0.7Rh_0.3O₃ electrocatalysts with x = 0.3 showed enhanced electrocatalytic bifunctional performance with a substantially lower OER/ORR onset potential of 1.38/0.73 V vs HRE, smaller Tafel slope (116/90 mV/dec), and low charge-transfer resistance, which is the most efficient catalyst among the other studied ratios and superior to the pristine lanthanum cobalt oxide benchmark electrocatalysts. The LaCo_0.7Rh_0.3O₃ electrode exhibit good bifunctional electrocatalytic behavior and long-term durability with an OER and ORR onset potential gap (ΔE = E_OER ? E_ORR) of only 0.65 V, which could be credited to the enriched oxygen vacancies, lattice expansion and the improved electrical conductivity upon the doping of larger size of Rh ions. The LaCo_1-xRh_xO₃ catalysts are obtained from abundant materials that have the potential of highly-active bifunctional OER and ORR electrocatalysts.     

La掺杂TiO2负载Pt催化剂制备及其室温氧化低浓度甲醛

甲醛是室内装修污染的重要组分,已严重危害到人们身体健康,在室温条件下消除甲醛引起了人们的广泛兴趣.目前室温清除甲醛主要有物理吸附法、光催化法、等离子体技术及催化氧化技术.物理吸附法主要采用活性炭等作为吸附剂,其初期吸附效果较好,但当吸附饱和之后会重新释放甲醛造成二次污染;光催化法和等离子体技术需要特殊装置,不适合室内室温环境脱除甲醛;而催化氧化技术则可直接将甲醛转化为无毒无害的水和CO2,因而备受关注.Pt/TiO2被认为是目前消除甲醛最有效的催化剂.为进一步降低贵金属Pt的用量及增强其稳定性(Pt被氧化后其活性会降低),本文首次采用稀土La掺杂锐钛矿型TiO2,负载少量Pt后用于室内低浓度(0.5 ppm)甲醛的催化氧化.活性测试结果表明,纯TiO2催化剂上甲醛转化率在5%以下,有可能是物理吸附或可见光催化所致.负载0.5%Pt后,Pt/TiO2和Pt/La-TiO2甲醛转化率均高于80%,尤其是La掺杂活性高达96%以上,且在连续反应8 h甚至延长至40 h后其活性均未见下降趋势.电镜结果表明,La掺杂Pt/La-TiO2催化剂中Pt粒径从未掺杂的2.2 nm降至1.7 nm;CO程序升温脱附测试表明,Pt/La-TiO2/Pt的分散度达66%,而未掺杂样品仅为51%;X射线光电子能谱测试表明,Pt/La-TiO2的表面氧物种高于Pt/TiO2催化剂,说明La掺杂增强了Pt和载体间的相互作用.为探讨Pt/La-TiO2商业化应用前景,将粉体Pt/La-TiO2涂覆在堇青石蜂窝陶瓷上制备成整体催化剂.该整体催化剂在容积为2 m3的密室测试中5 min内即可将浓度为0.5 ppm的甲醛将至0.02 ppm以下.该催化剂在存放3个月后活性略有下降,但在10 min内仍可将甲醛浓度降至0.08 ppm,达到室内甲醛排放标准.综上,本文成功制备了La掺杂Pt/La-TiO2用于室内低浓度甲醛催化氧化,该催化剂表现出优异的催化性能.通过多种表征手段表明,La修饰后贵金属Pt纳米粒子尺寸减小、分散度提高及Pt与载体间相互作用增强是其活性优异的主要原因.以Pt/La-TiO2粉体制备的整体催化剂同样表现出了高的催化性能,具有工业应用前景.     

微波等离子体炬原子发射光谱法测定铁增敏效应

针对在低功率下工作的微波等离子体炬原子发射光谱法(MPT-AES)存在对一些元素检测灵敏度较低和抗基体干扰能力弱的问题,以氩气为载气和工作气,研究了表面活性剂及镧盐对MPT-AES测定铁的增敏效应,考察了铁测定的工作条件和共存元素对铁测定的影响.实验结果表明,非离子表面活性剂对铁的测定有抑制作用,而阳离子表面活性剂和镧盐对铁的测定有增敏作用,其中镧盐增敏效果最好.以镧盐为增敏剂,不仅可提高MPT-AES测定铁的灵敏度,还可增加共存元素的允许量.当体系中镧浓度为0.500 mg/m L时,至少可使40倍的锌,30倍的钴,20倍的镍、锰,15倍的钙,10倍的镁、铜和钠不影响铁的测定.与不加镧时相比,铁的发射强度提高了2.4倍,检出限由原来的27.5×10~(-3)μg/m L下降为8.5×10~(-3)μg/m L.将本方法应用于原油样品中铁的测定,所得结果与火焰原子吸收光谱法测定结果一致.     

Oxidative dehydrogenation of ethylbenzene over γ-Al2O3 supported ceria-lanthanum oxide catalysts: Influence of Ce/La composition

A series of CeO₂/γ-Al₂O₃ (CA) catalysts with CeO₂ loading of 5, 10, 15 and 20 wt% were prepared by a facile incipient wetness impregnation technique. Another series of La³⁺ doped catalysts (LCA) were prepared, wherein, 1, 3 and 5 wt% of La₂O₃ was doped in 15 wt%CeO₂/γ-Al₂O₃, which were designated as 1LCA, 3LCA and 5LCA catalysts. Both CA and LCA catalysts were characterized by thermogravimetric analysis (TGA), BET surface area, X-ray diffraction (XRD), Infrared (FT-IR) spectroscopy, UV–vis diffuse reflectance spectra (UV–vis DRS), transmission electron microscopy (TEM), temperature programmed desorption of NH₃ (TPD of NH₃) temperature programmed reduction (TPR), CO₂ pulse chemisorption and O₂ pulse chemisorption techniques. All CA and LCA catalysts were evaluated for ethylbenzene (EB) oxidative dehydrogenation to styrene (ST) in vapor phase under atmospheric pressure with CO₂ as an oxidant. Albeit CA and LCA catalysts are active, 15CA and 3LCA catalysts are found to be the best catalysts of the respective series. Apart from compatible acid-base and redox characteristics, sufficient amount of solid solution clusters (Ce_xLa_1-xO_2-δ) are responsible for superior activity of 3LCA catalyst.     

Electrical conductivities and microstructures of LSM,LSM-YSZ and LSM-YSZ/LSM cathodes fabricated on YSZ electrolyte hollow fibres by dip-coating

Lanthanum strontium manganite – La_0.80Sr_0.20MnO₃ (LSM), LSM-Yttria stabilised zirconia (LSM-YSZ) composite and LSM-YSZ/LSM double-layer cathodes were separately fabricated on Yttria stabilised zirconia (YSZ) electrolyte hollow fibres by dip coating; their electrical conductivities and microstructures were then determined by the direct current four-probe method and scanning electron microscopy (SEM), respectively. Excellent cathode-electrolyte and cathode-cathode adhesion without delamination were achieved by the dip-coating fabrication method. The apparent electrical conductivities of porous LSM, LSM-YSZ and LSM-YSZ/LSM cathodes manufactured on YSZ hollow fibre by dip-coating and sintered at various temperatures in the range 1273–1473 K for 3 h, were 1.8 × 10³–5.5 × 10³ S/m, 0.32–209 S/m and 1.3 × 10³–5.5 × 10³ S/m, respectively, at measurement temperatures of 673–1073 K. The operating temperature dependence of the apparent electrical conductivity of the LSM, LSM-YSZ and LSM-YSZ/LSM cathodes was defined by the Arrhenius equation for electrical conductivity. The activation energies for electrical conductivity were derived as 0.106–0.147 eV, 0.83–0.94 eV, and 0.104–0.146 eV for the LSM, LSM-YSZ and LSM-YSZ/LSM cathodes, respectively. The LSM-YSZ and LSM-YSZ/LSM cathodes were strongly influenced by the YSZ and LSM phases, respectively.     

镧掺杂的二氧化锰/碳纳米管电化学超级电容器复合电极

尽管在二氧化锰/多壁碳纳米管（MnO₂/MWCNTs）上获得了较高的比电容,低电导率仍是制约MnO₂担载量或膜厚度提高的主要障碍.另一个问题是MnO₂/MWCNTs的循环稳定性远低于活性炭.所以截止到目前这一新型材料的应用仍然受到很大的限制.本文采用原位还原的方法制备镧掺杂二氧化锰/多壁碳纳米管电化学超级电容器复合电极材料.分别通过透射电镜（TEM）、扫描电镜（SEM）、X射线衍射（XRD）和傅里叶变换红外（FTIR）光谱等技术对这些复合材料的形貌与结构进行了分析.采用循环伏安法、恒电流充放电法和交流阻抗法对其进行了电化学性能的研究.研究结果表明,通过还原MnO₄^-可以在MWCNTs上形成La掺杂MnO₂复合材料.La掺杂降低了复合电极的电阻,这是因为La的引入可以增大MnO₂的晶格缺陷,从而提高材料的电导率以及电极的电化学性能.因此La掺杂是克服MnO₂本征导电性差的有效途径之一.掺杂La可以在不增大电极电阻的情况下提高MnO₂的担载量或膜厚度.La掺杂的更重要的作用是使以MnO₂/MWCNTs作电极的对称电化学超级电容器的循环性能得到显著改善.此外,La掺杂也使复合电极的比电容得到一定程度的提高.     

Crystal structure of Eu-doped magnetoplumbite-type lanthanum aluminum oxynitride with emission site splitting

Eu-doped lanthanum aluminum oxynitride (LaAl₁₂(O,N)₁₉) with magnetoplumbite structure was prepared by nitridation of the oxide precursor obtained from aluminum glycine gel and subsequent post-annealing. Eu-doped lanthanum aluminum oxynitride exhibited blue light emission at 440 nm with a shoulder at 464 nm under excitation at 254 nm. Isostructural Eu-doped calcium aluminum oxide (CaAl₁₂O₁₉) exhibited a single emission peak at 415 nm. Structural refinement using neutron powder diffraction indicated that the lanthanum site occupied partially by Eu²⁺ splits into 2d and 6h sites in the aluminum oxynitride. The longer emission and the shoulder peak in the former aluminum oxynitride were observed in relation to the increasing covalency as well as crystal field splitting around doped Eu²⁺ induced by site splitting involved with the two kinds of anions.     

Si epitaxial growth on LaAlO3(0 0 1)

We report on the growth of Si on c(2 × 2) reconstructed LaAlO₃(0 0 1) surfaces at high substrate temperature (700 °C) by molecular beam epitaxy. An initial Volmer-Weber mode is evidenced using reflection high energy electron diffraction (RHEED), X-ray photoelectron diffraction (XPD) and atomic force microscopy. After the deposition of a few monolayers, the islands coalesce. Using X-ray photoelectron spectroscopy, we demonstrate that Si islands exhibit an abrupt interface with the LaAlO₃ substrate without formation of silicate or silica. Finally, combined RHEED and XPD measurements show the epitaxial growth of Si with a unique Si(0 0 1)//LaAlO₃(0 0 1) and Si<1 0 0>//LAO<1 1 0> relationship.