Pd/Co双金属纳米颗粒的制备及催化制氢性能

采用聚乙烯吡咯烷酮(PVP)保护的化学共还原法制备了Pd/Co双金属纳米颗粒, 研究了PVP及还原剂(NaBH₄)的用量、金属盐浓度、金属比例等对Pd/Co双金属纳米颗粒催化NaBH₄制氢性能的影响. 透射电子显微镜(TEM)的结果表明, 所制备的Pd/Co双金属纳米颗粒的平均粒径在1.5-2.8 nm之间. Pd/Co双金属纳米颗粒(BNPs)的催化活性远高于Pd与Co单金属纳米颗粒的活性; 当Pd/Co的理论原子比为1/9时, 双金属纳米颗粒的催化活性最高可达15570 mol·mol^-1·h^-1 (文中纳米颗粒的催化活性均为每摩尔Pd的活性). 密度泛函理论(DFT)的计算结果表明, Pd原子与Co原子之间发生电荷转移, 使得Pd原子带负电而Co原子带正电, 荷电的Pd和Co原子进而成为催化反应的活性中心. 所制备的Pd/Co双金属纳米颗粒具有很好的催化耐久性, 即使重复使用5次后, 该催化剂仍具有较高的催化活性, 且使用后的纳米颗粒催化剂也没有出现团聚现象. 双金属纳米颗粒催化NaBH₄水解反应的活化能约为54 kJ·mol^-1.     

石墨烯负载Pt-Pd催化剂的制备、催化制氢性能及机理研究

以氧化石墨烯为载体,采用乙醇共还原法制备了石墨烯负载Pt-Pd双金属纳米催化剂,并将其用于催化碱性硼氢化钾(KBH_4)水解制氢研究.采用X射线衍射(XRD)分析和透射电子显微镜(TEM)等手段表征了催化剂的微观形貌和结构,发现当金属催化剂中Pt/Pd摩尔比为1∶1时,Pt-Pd双金属催化剂颗粒可均匀地负载于石墨烯载体表面,而且粒径比单金属催化剂和其它组成的双金属催化剂粒径更小,约为5.6 nm.将该催化剂用于催化碱性条件下KBH_4水解制氢实验,结果表明,金属催化剂的化学组成对其催化性能有明显影响,当Pt/Pd摩尔比为1∶1时其催化活性高于其它化学组成(Pt/Pd摩尔比为4∶1或1∶4)的Pt-Pd双金属催化剂,催化活性可达4380 mol_(H2)·mol_M~(-1)·h~(-1),比Pt单金属催化剂活性提高约52%,为Pd单金属催化剂活性的4倍.通过催化反应动力学研究发现,Pt-Pd双金属催化剂催化KBH_4水解制氢反应的活化能约为20.90k J/mol,催化剂具有较佳的耐久性,连续使用3次后催化效率仍可达首次催化反应效率的83%.利用密度泛函理论研究了催化剂催化KBH_4水解反应的机制,发现双金属纳米催化剂可以明显降低硼氢化物水解反应决速步骤基元反应的势垒,从而显著提高催化剂的催化活性.     

Rh/Co双金属纳米颗粒的制备及其催化制氢性能

以ISOBAM-104为保护剂,采用共还原法制备了一系列不同组成的Rh/Co双金属纳米颗粒(BNPs)。采用紫外-可见吸收光谱、透射电镜及高分辨透射电镜对纳米颗粒的结构及组成进行了表征。结果表明,所制备的Rh/Co BNPs的粒径小于6.0nm,具有合金结构。催化制氢实验结果表明,Rh_(20)Co_(80)BNPs具有最高的催化制氢活性,其TOF值可高达12880mol-H_2·h~(-1)·mol-Rh~(-1),远高于Rh和Co单金属纳米颗粒的催化活性。     

Pt/Ni/Fe三金属纳米颗粒的制备及催化制氢活性

采用化学共还原方法制备了聚乙烯吡咯烷酮(PVP)保护的Pt/Ni/Fe三金属纳米颗粒,对所合成的纳米颗粒进行了表征,研究了三金属纳米颗粒的化学组成对其催化NaBH4制氢的影响.研究结果表明,Pt/Ni/Fe三金属纳米颗粒的平均粒径在2 nm左右,Pt/Ni/Fe三金属纳米颗粒催化活性高于Pt,Ni或Fe单金属纳米颗粒和Pt/Ni,Pt/Fe或Ni/Fe双金属纳米颗粒的催化活性,其中Pt10Ni78.75Fe11.25三金属纳米颗粒的催化活性最高,30℃时,其催化活性可达63.920×103molH2/(molPt·h).Pt/Ni/Fe三金属纳米溶胶催化剂具有很好的催化稳定性,10次重复催化实验后,该催化剂依然可以保持较高的催化活性.该三金属纳米溶胶催化NaBH4水解反应的活化能为52 kJ/mol.     

单原子铂催化剂的制备及其低温催化氧化一氧化碳

以氧化石墨烯为载体,单原子铂（Pt）为活性组分,利用化学还原法制备了单原子Pt/rGO催化剂,用在催化氧化一氧化碳（CO）反应中。通过透射电子显微镜、扫描电子显微镜、球差电镜、傅里叶红外光谱仪对单原子Pt催化剂进行表征。考察了金属负载量、反应温度对催化剂性能的影响,利用气相色谱对CO氧化反应性能进行评价。此次实验包含催化剂的制备、表征和性能测试,实验难度适中,贴近科研前沿,可以让学生体验一个综合的科研过程,激发学生的科研兴趣,培养学生的科研能力。     

Pt/Ni双金属纳米溶胶的制备及催化制氢性能

采用化学共还原法制备了聚乙烯吡咯烷酮(PVP)稳定的Pt/Ni双金属纳米溶胶.采用紫外-可见光谱(UV-Vis)、透射电子显微镜(TEM)对所合成的Pt/Ni双金属纳米溶胶进行了表征, 并系统研究了PVP用量、还原剂用量和浓度、双金属比例对该双金属纳米溶胶催化剂催化性能的影响.结果表明, 所制备的双金属纳米溶胶的平均粒径在2.0 nm左右, Pt/Ni双金属纳米溶胶的催化活性比Pt及Ni单金属纳米溶胶的高, 当Pt/Ni摩尔比为1:4时, 纳米溶胶的催化活性最高, 其活性值为16640 mol_H2·mol_Pt^-1·h^-1.所制备的Pt/Ni双金属纳米溶胶催化剂具有很好的耐久性, 5次催化实验后该催化剂仍保持较高的催化活性.该双金属纳米溶胶催化NaBH₄水解反应的活化能为48 kJ/mol.     

石墨烯负载Pt/Co双金属纳米颗粒催化剂的制备及催化制氢性能

采用化学共还原方法制备了石墨烯负载Pt/Co双金属纳米颗粒（GBNPS）催化剂,并将其用于催化硼氢化钾（KBH₄）水解制氢.采用透射电子显微镜（TEM）、X射线衍射（XRD）仪和X射线光电子能谱（XPS）表征了该催化剂,并研究了双金属纳米颗粒的化学组成对其催化KBH₄水解制氢性能的影响.结果表明,制备的石墨烯负载Pt/Co双金属纳米颗粒平均粒径为3.2~3.9 nm,其中石墨烯负载Pt₂₀Co₈₀双金属纳米颗粒的催化活性最高,35℃时制氢活性可达35973 mol_H2·h^-1·mol^-1_Pt,且具有良好的耐久性,催化KBH₄水解反应的表观活化能为36 kJ/mol.     

配位环境可调的Cu单原子的合成及催化加氢性能研究※

具有可控配位环境的高催化活性和选择性的稳定单金属位点催化剂的合成仍然具有挑战性. 本工作采用阳离子交换策略合成了两种具有不同配位结构的Cu单原子催化材料. 该策略主要依赖于硫化物的阴离子骨架和富含 N 的聚合物壳在高温退火过程中产生大量的S和N缺陷, 精确合成了富边缘S和N双修饰的单金属Cu位点催化材料. 在这两种材料, 一种Cu单原子具有硫(S)、氮(N)双配位, 一种Cu单原子只有单一的S配位. Cu中心原子的第一壳层配位数为4, Cu-S/N-C的结构为Cu-S₁N₃, Cu-S-C的结构为Cu-S₄. 实验表明, S、N双修饰的Cu单原子材料在室温下催化硝基苯加氢过程中表现出较高活性. 反应20 min后, 在Cu-S/N-C催化下, 硝基苯加氢转化率达到100%, 循环使用5次后活性未见显著下降. 该发现为调节中心金属配位环境以提高单原子催化材料的性能提供了一种可行的方法.     

单原子催化材料在电化学氢循环应用中的研究进展

单原子催化剂(SACs)是一类仅含有孤立的单个金属原子作为催化活性中心的催化材料. 由于其具有100%的原子利用率、 独特的化学结构及优异的催化活性等优点, 近年来在电化学催化和电能转换设备领域备受关注. 本文综合评述了单原子催化材料的设计理念、 合成方法和表征方法, 同时对其在氢电化学循环 (电解水制氢和氢燃料电池领域)的实际应用进行了系统介绍, 并对单原子催化材料的研究和应用前景进行了展望.     

铂单原子催化剂同步辐射X射线吸收谱的研究进展

相比于传统块体材料, 铂单原子催化剂(Pt SACs)具有接近100%的贵金属利用率、 优异的催化活性和均一的反应位点等优势, 近年来逐渐成为催化研究的前沿之一. 高度分散的Pt原子与载体之间的界面相互作用很大程度上决定了Pt SACs的物理和化学性能. 因此, 建立金属-载体相互作用与性能之间的内在关联机制, 对于单原子催化剂的优化设计至关重要. 得益于同步辐射光源高亮度、 高准直性和宽波谱的优势, X射线吸收谱技术在鉴别单原子催化剂的电子结构和局域配位方面的成果显著. 本文综合评述了Pt SACs X射线吸收谱的研究进展, 重点介绍了Pt与金属氧化物、 金属、 纳米碳和多孔有机框架等载体之间独特的相互作用， 以及其对性能的影响机制, 并对未来同步辐射新技术在Pt SACs的高分辨解析方面的前景进行了展望.     

Sol-gel synthesis of K3InF6 and structural characterization of K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18

K₃InF₆ is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K₂InC₁₀O₁₀H₆F₉, K₃InC₁₂O₁₄H₄F₁₈ and K₃InC₁₂O₁₂F₁₈. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K₃InF₆ by decomposition at high temperature. The crystal structure of K₃InC₁₂O₁₄H₄F₁₈ is characterized by complex anions [In(CF₃COO)₄(OH_x)₂]^(5−2x)− and isolated [CF₃COOH_2−x]^(x−1)− molecules with x=2 or 1, surrounded by K⁺ cations. The crystal structure of K₃InC₁₂O₁₂F₁₈ is only constituted by complex anions [In(CF₃COO)₆]³⁻ and K⁺ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K₂InC₁₀O₁₀H₆F₉ and K₃InC₁₂O₁₂F₁₈ were also performed at room temperature on pulverized crystals.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

Structure Study of Bi2.5Na0.5Ta2O9 and Bi2.5Nam−1.5NbmO3m+3 (m=2-4) by Neutron Powder Diffraction and Electron Microscopy

The crystal structures of Bi_2.5Na_0.5Ta₂O₉ and Bi_2.5Na_m-1.5Nb_mO_3m+3 (m=3,4) have been investigated by the Rietveld analysis of their neutron powder diffraction patterns (λ=1.470 Å). These compounds belong to the Aurivillius phase family and are built up by (Bi₂O₂)²⁺ fluorite layers and (A_m-1B_mO_3m+1)^2- (m=2-4) pseudo-perovskite slabs. Bi_2.5Na_0.5Ta₂O₉ (m=2) and Bi_2.5Na_2.5Nb₄O₁₅ (m=4) crystallize in the orthorhombic space group A2₁am, Z=4, with lattice constants of a=5.4763(4), b=5.4478(4), c=24.9710 (15) and a=5.5095(5), b=5.4783(5), c=40.553(3) Å, respectively. Bi_2.5Na_1.5Nb₃O₁₂ (m=3) has been refined in the orthorhombic space group B2cb, Z=4, with the unit-cell parameters a=5.5024(7), b=5.4622(7), and c=32.735(4) Å. In comparison with its isostructural Nb analogue, the structure of Bi_2.5Na_0.5Ta₂O₉ is less distorted and bond valence sum calculations indicate that the Ta-O bonds are somewhat stronger than the Nb-O bonds. The cell parameters a and b increase with increasing m for the compounds Bi_2.5Na_m-1.5Nb_mO_3m+3 (m=2-4), causing a greater strain in the structure. Electron microscopy studies verify that the intergrowth of mixed perovskite layers, caused by stacking faults, also increases with increasing m.     

Magnetic properties of Ca2F2-xMnxO5

Magnetic susceptibility of Ca₂F_2-xMn_xO₅ members crystallizing in two different structures, one having octahedral (O), tetrahedral (T) and square-pyramidal (SP) coordination of transition metal atoms (OTSP structure) and the other having octahedral and tetrahedral coordination (OT structure), has been investigated. Susceptibility behaviour of the oxides with OTSP structure is different from that of the oxides with OT structure. Ca₂Fe_1-33Mn_0-67O₅ with OTSP structure shows an antiferromagnetic ordering while the corresponding oxide with OT structure shows weak ferromagnetism. Contribution No. 398 from the Solid State and Structural Chemistry Unit     

La3Ru8B6 and Y3Os8B6, new members of a homologous series R(A)nM3n−1B2n

Two new compounds, La₃Ru₈B₆ and Y₃Os₈B₆, were synthesized by arc melting the elements. Their structural characterization was carried out at room temperature on as-cast samples by using X-ray diffractometry. According to X-ray single-crystal diffraction results these borides crystallize in Fmmm space group (no. 69), Z=4, a=5.5607(1) Å, b=9.8035(3) Å, c=17.5524(4) Å, ρ=8.956 Mg/m³, μ=25.23 mm⁻¹ for La₃Ru₈B₆ and a=5.4792(2) Å, b=9.5139(4) Å, c=17.6972(8) Å, ρ=13.343 Mg/m³, μ=128.23 mm⁻¹ for Y₃Os₈B₆. The crystal structure of La₃Ru₈B₆ was confirmed from Rietveld refinement of X-ray powder diffraction data. Both La₃Ru₈B₆ and Y₃Os₈B₆ compounds are isotypic with the Ca₃Rh₈B₆ compound and their structures are built up from CeCo₃B₂-type and CeAl₂Ga₂-type structural fragments taken in ratio 2:1. They are the members of structural series R(A)_nM_3n−1B_2n with n=3 (R is the rare earth metal, A the alkaline earth metal, and M the transition metal). Structural and atomic parameters were also obtained for La_0.94Ru₃B₂ compound from Rietveld refinement (CeCo₃B₂-type structure, P6/mmm space group (no. 191), a=5.5835(9) Å, c=3.0278(6) Å).     

The crystal chemistry of Bi6TP2O15+x, T=Fe, Ni, Zn: Isomorphism and polymorphism, structural relationship to Bi6TiP2O16

The crystal structures of compounds with nominal compositions Bi₆FeP₂O_15+x (I), Bi₆NiP₂O_15+x (II) and Bi₆ZnP₂O_15+x (III) were determined from single-crystal X-ray diffraction data. They are monoclinic, space group I2, Z=2. The lattice parameters for (I) are a=11.2644(7), b=5.4380(3), c=11.1440(5) Å, β=96.154(4)°; for (II) a=11.259(7), b=5.461(4), c=11.109(7) Å, β=96.65(1)°; for (III) a=19.7271(5), b=5.4376(2), c=16.9730(6) Å, β=131.932(1)°. Least squares refinements on F² converged for (I) to R1=0.0554, wR₂=0.1408; for (II) R₁=0.0647, wR₂=0.1697; for (III) R₁=0.0385, wR₂=0.1023. The crystals are complexly twinned by 2-fold rotation about , by inversion and by mirror reflection. The structures consist of edge-sharing articulations of OBi₄ tetrahedra forming layers in the a-c plane that then continue by edge-sharing parallel to the b-axis. The three-dimensional networks are bridged by Fe and Ni octahedra in (I) and (II) and by Zn trigonal bipyramids in (III) as well as by oxygen atoms of the PO₄ moieties. Bi also randomly occupies the octahedral sites. Oxygen vacancies exist in the structures of the three compounds due to required charge balances and they occur in the octahedral coordination polyhedron of the transition metal. In compound (III), no positional disorder in atomic sites is present. The Bi-O coordination polyhedra are trigonal prisms with one, two or three faces capped. Magnetic susceptibility data for compound (I) were obtained between 4.2 and 350 K. Between 4.2 and 250 K it is paramagnetic, μ_eff=6.1 μ_B; a magnetic transition occurs above 250 K.     

一维纳米Co_3O_4,Ag/Co_3O_4及CuO/Co_3O_4的合成与电催化性能(英文)

采用水热合成法制备了Co3O4及复合Ag/Co3O4、CuO/Co3O4一维纳米产品。用XRD,FE-SEM和TEM手段对产品进行了表征。采用循环伏安法研究了合成产品修饰的玻碳电极在碱性溶液中对对硝基苯酚的电催化还原性能。与裸玻碳电极相比,1mmol·L-1的对硝基苯酚在用Co3O4、特别是CuO/Co3O4修饰的玻碳电极上还原的峰电流明显增大,用Ag/Co3O4(Ag/Co原子比分别为1∶5和2∶5)修饰的玻碳电极催化还原对硝基苯酚时,尽管还原峰电流增大不是太大,但其峰电位明显降低(分别降低0.265和0.371V)。     

Transmission electron microscopy study of Ruddlesden-Popper Can+1MnnO3n+1n=2 and 3 compounds

Two Ruddlesden-Popper compounds Ca_n+1Mn_nO_3n+1 with n=2 and 3 synthesized by a citrate gel technique have been studied by TEM. The structure of Ca₄Mn₃O₁₀ is consistent with the previously determined structure having the space group Pbca and a⁻ a⁻ c⁺/a⁻ a⁻ c⁺ tilt system. The presence of defects suggests the possible high-temperature phase transition from untilted I4/mmm to Pbca. The structure of Ca₃Mn₂O₇ was found to be different from the previously suggested I4/mmm symmetry. Ca₃Mn₂O₇ forms with an orthorhombic structure with either Cmcm or Cmc2₁ space group. A structural model for Cmc2₁ based on the tilting of almost-rigid octahedra with a⁺ c⁻ c⁻/a⁺ c⁻ c⁻ tilt system is proposed. The lamellar defects were shown to be twin variants of the Cmc2₁ structure with the (001)_t interfaces, which suggests the possible tilting phase transition from the ideal I4/mmm to Cmc2₁ following the maximal group-subgroup symmetry tree: I4/mmm→Fmmm→Bbmm(Cmcm)→Bb2₁m(Cmc2₁).     

Ag/Ag2MoO4/Bi2MoO6复合光催化剂的制备及其光催化性能

采用水热、化学沉积和原位光还原的方法成功制备了新型Ag/Ag₂MoO₄/Bi₂MoO₆三元复合光催化剂。通过X射线粉末衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）和紫外可见漫反射光谱（UV-Vis DRS）等技术对材料的组成、形貌、光吸收特性和光电化学性能等进行系统分析。以四环素为目标污染物,研究Ag/Ag₂MoO₄/Bi₂MoO₆在可见光下的光催化性能。研究结果表明,相比于纯Ag₂MoO₄和Bi₂MoO₆,Ag的表面等离子体共振（SPR）效应显著拓宽了催化体系对可见光的吸收能力及响应范围。当Ag₂MoO₄理论负载量（质量分数）为24.6%时,Ag/Ag₂MoO₄/Bi₂MoO₆复合材料在20 min内可将四环素完全降解,且5次循环使用后仍保持较高的催化活性,表现出良好的循环稳定性。     

Metal-organic deposition of YBa2Cu3Ox and Bi2Sr2Ca1Cu2Ox films on various substrates starting from different fluorine-free metallorganic compounds

YBa₂Cu₃O_x (Y-123) and Bi₂Sr₂Ca₁Cu₂O_x (Bi-2212) films on various substrates have been prepared by Metal-Organic Deposition starting from different metallorganic fluorine-free compounds and using a very simple instrumentation. The processing conditions include a rapid pyrolysis step in air and an annealing step in oxygen for Y-123 and in air for Bi-2212. The films obtained have been characterized by X-ray diffraction (XRD) and the formation of a superconducting phase of Y-123 or Bi-2212 was confirmed measuring the critical temperature (T _c) with Ac-susceptibility and resistive measurements. Microstructure and final cationic ratios have been studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).