聚酰亚胺上催化剂增强化学气相沉积钯-铂双层膜

 以N2和O2为载气,采用催化剂增强化学气相沉积法于聚酰亚胺上获得了Pt和Pd-Pt双层金属薄膜. 当使用Pd(hfac)2和PtMe2(COD)为前驱体,在同一反应器内共沉积时,只有Pt被沉积. 金属Pd和Pt顺序沉积可形成Pd-Pt双层膜.     

催化增强化学蒸气沉积法在聚酰亚胺上沉积钯-铂合金薄层

以N₂，O₂作载气，通过催化增强化学蒸气沉积(CECVD)分别制得在聚酰亚胺上的金属铂、钯及其合金薄层。铂、钯配合物的共同沉积可生成Pt-Pd合金薄膜。在Pd-Pt合金的沉积过程中，Pd/Pt的原子数比率随共同沉积的条件改变而变化。O₂为载气、300 ℃条件下,用Pd(η³-allyl)(hfac)和Pt(COD)Me₂作前驱体共沉积制备Pd-Pt合金，得到含Pd 37.2%，Pt 62.8%且不     

双硫腙萃取双波长系数倍率法测定铂和钯的研究及应用

在1mol/L盐酸溶液中,当氯化亚锡存在时,用双硫腙溶液同时萃取铂和钯,双波长系数倍率法测定。测定铂时,λ_1为600nm、λ_2为710nm,K=7,测定钯时,λ_1为720nm。λ_2为638nm,K=3.5。铂和钯均在0～1.0μg/ml浓度范围内符合比尔定律,表观摩尔吸光系数分别为2.01×10~5L·mol~(-1)·cm~(-1)和1.10×10~5L·mol~(-1)·cm~(-1)。本文还探讨了氯化亚锡在萃取反应中的作用机理。方法简便、选择性好,用于地质样品中痕量铂和钯的测定,可获得满意的结果。     

氮铂共掺杂纳米二氧化钛的制备及表征

采用溶胶-凝胶法制备了氮掺杂纳米TiO2(N-TiO2),并用光分解沉积法在N-TiO2表面负载上微量金属Pt形成铂-氮共掺杂纳米TiO2(Pt/N-TiO2).通过X射线衍射、光电子谱、紫外-可见吸收、扫描电镜和光电流测试对催化剂进行了表征.结果表明:Pt和N共掺杂对TiO2的晶型和形貌影响不大,但其吸收边带较纳米TiO2约红移20nm,Pt/N-TiO2电极在可见光区的光电流约为纳米TiO2电极的4倍.     

碳纳米管负载金属Pt催化剂的制备和机理研究

本文报道了高温裂解法沉积铂纳米颗粒于碳纳米管壁的新方法。利用红外光谱技术考察了碳纳米管壁的官能团衍生化以及这些官能团与铂颗粒沉积间的关系。利用透射电镜(TEM)、X-射线粉末衍射(XRD)以及光电子能谱技术(XPS)对碳纳米管壁上负载的铂纳米颗粒进行了表征。结果表明，大小约为5 nm的铂纳米颗粒以金属Pt(0)的形式均匀分散在纳米管表面，主要晶面定向为(111)面。同时，考察了甲醇在碳纳米管负载铂纳米颗粒复合材料电极上的电催化氧化。     

铂-氧化铈/聚苯胺/聚砜复合膜电极的制备及对甲醇的电催化氧化

采用电化学聚合法制备了掺杂CeO2纳米粒子的聚苯胺(PAN)/聚砜(PSF)复合膜电极,在其上电沉积铂粒子,制得了铂-氧化铈/聚苯胺/聚砜的复合膜修饰电极。 复合膜的形貌和化学组分通过冷场发射扫描电子显微镜（Cold FE-SEM）和能量散射X射线谱（EDS）进行了表征,用循环伏安法和电化学交流阻抗法考察了复合膜电极对甲醇的电催化氧化性能。 结果表明,复合膜的双层多孔结构使铂粒子与CeO2粒子在复合膜内层的多孔聚苯胺上均匀沉积,粒子平均尺寸约为80 nm;CeO2为铂质量的7%时,铂-氧化铈/聚苯胺/聚砜复合膜修饰电极对甲醇有很好的电催化氧化性能和高的稳定性。     

电化学方法制备高分散Pt/CMK-3及其对甲醇电化学催化性能

采用直接电化学还原法在介孔碳(CMK-3)载体上直接电沉积高分散的铂纳米颗粒,制备CMK-3复合铂纳米颗粒电极(Pt/CMK-3)。 通过透射电子显微镜分析发现,铂纳米颗粒非常均匀的分布在CMK-3上,平均粒径约5 nm。 通过循环伏安测试,分析了催化剂不同负载铂含量时氯铂酸的利用率,在理论铂质量分数为20%时,这种方法制备的Pt/CMK-3所使用的氯铂酸的利用率最高,在1 mol/L CH3OH+0.5 mol/L H2SO4溶液中循环伏安测试电流密度达到382 A/g。 在相同实验条件下,Pt/CMK-3电极对甲醇电催化活性远高于Pt/XC-72(炭黑)电极和用常规电沉积方法制备的Pt/CMK-3电极。     

低温静电自组装法制备贵金属修饰TiO_2纳米结构薄膜及其增强的光催化性能(英文)

以碱-水热法在金属Ti片上原位生长了TiO2纳米结构(纳米花和纳米线)薄膜,并采用低温静电自组装方法将超细贵金属(金、铂、钯)纳米颗粒均匀沉积于多孔TiO2薄膜上.负载于Ti片上的贵金属/TiO2纳米结构薄膜具有一体化结构、多孔架构和高光催化活性.超高分辨率场发射扫描电子显微镜(FESEM)直接观察表明贵金属纳米颗粒在TiO2表面分布均匀,且颗粒之间相互分离,金、铂、钯纳米颗粒的平均粒径分别约为4.0、2.0和10.0nm.俄歇电子能谱(AES)纵深成分分析表明贵金属不仅沉积于薄膜表面,且大量分布于TiO2纳米结构薄膜内部,其深度超过580 nm.X射线光电子能谱(XPS)分析表明,经300°C下在空气中热处理后,纳米金仍保持金属态,纳米铂部分被氧化成PtOabs,而钯粒子则完全被氧化成氧化钯(PdO).以低温静电自组装法沉积贵金属,贵金属负载量可通过调节组装时间与溶胶pH值来控制.光催化降解甲基橙的结果表明,沉积的纳米金和铂能显著增加TiO2纳米结构薄膜的光催化活性,说明金和铂粒子可促进光生载流子的分离;但负载的PdO对TiO2薄膜的光催化性能增强几乎无作用.     

Pt-H_xWO_3复合电极的制备及其对氧还原的电催化

应用电位扫描法制备3种铂与氢钨青铜(HxWO3)的复合电极,即铂上沉积氢钨青铜(HxWO3/Pt),氢钨青铜上沉积铂(Pt/HxWO3)及铂和氢钨青铜共沉积(Pt-HxWO3).测试结果表明,氢钨青铜能显著提高铂电催化对氧还原的活性,其中以复合电极Pt/HxWO3的电催化活性最高,这可能是因为在玻碳基底上先电沉积氢钨青铜再电沉积铂增加了铂的有效比表面,该电极制备为减少铂用量提供一条有效途径.     

不同Pt壳厚度Au_(core)@Pt_(shell)纳米粒子SERS效应

以Au粒子(55nm)为核,抗坏血酸为还原剂,将不同量的Pt沉积在Au核上,制得可控壳层厚度(0.3～6nm)的Pt包Au纳米粒子(Aucore@Ptshell).用紫外-可见吸收光谱、扫描电镜(SEM)、透射电镜(TEM)和电化学循环伏安法等观测Aucore@Ptshell纳米粒子的表面形貌、结构和性能.另以SCN-为探针,考察了Pt壳厚度对Aucore@Ptshell纳米粒子SERS信号的影响.结果表明,SCN-离子的SERS信号强度随Pt壳厚度的增加呈指数衰减,当Pt壳厚度为1.4nm时,Aucore@Ptshel纳米粒子表现出铂良好的电化学性能,又具有较强的SERS活性.     

柴油深度脱芳烃Pd-Pt/USY催化剂的EXAFS研究

为满足日趋严格的环保要求和适应汽车工业的快速发展,柴油深度脱芳烃已成为国内外普遍关注的课题．近年来的研究表明,Pd－Pt/USY催化剂具有较高的芳烃加氢活性和较强的耐硫中毒能力[’－     

Synthesis of Pd-Pt bimetallic nanocrystals with a concave structure through a bromide-induced galvanic replacement reaction

This article describes a systematic study of the galvanic replacement reaction between PtCl(6)(2-) ions and Pd nanocrystals with different shapes, including cubes, cuboctahedrons, and octahedrons. It was found that Br(-) ions played an important role in initiating, facilitating, and directing the replacement reaction. The presence of Br(-) ions led to the selective initiation of galvanic replacement from the {100} facets of Pd nanocrystals, likely due to the preferential adsorption of Br(-) ions on this crystallographic plane. The site-selective galvanic replacement resulted in the formation of Pd-Pt bimetallic nanocrystals with a concave structure owing to simultaneous dissolution of Pd atoms from the {100} facets and deposition of the resultant Pt atoms on the {111} facets. The Pd-Pt concave nanocubes with different weight percentages of Pt at 3.4, 10.4, 19.9, and 34.4 were also evaluated as electrocatalysts for the oxygen reduction reaction (ORR). Significantly, the sample with a 3.4 wt.% of Pt exhibited the largest specific electrochemical surface area and was found to be four times as active as the commercial Pt/C catalyst for the ORR in terms of equivalent Pt mass.     

有序介孔三氧化二锰负载PdPt合金:一种高效的甲烷催化燃烧催化剂

甲烷作为一种清洁廉价的碳氢能源,广泛应用于运输业和其它工业领域.但是其本身是一种比二氧化碳导致全球变暖效应更强的温室气体,而且甲烷直接燃烧会产生其它污染物,比如一氧化碳、氮氧化物、未充分燃烧的碳氢化合物等.因此有必要开展有关甲烷催化燃烧的研究工作,以大幅度降低起燃温度,提高燃烧效率,有效地减少污染副产物的产生.由于具有较好的低温催化活性,Pd基催化剂常用于甲烷的催化燃烧.但是Pd基催化剂也存在一些亟需解决的问题,比如在催化燃烧过程中活性相结构不稳定.PdO通常被认为是碳氢化合物催化氧化中的活性相,但是在高温下PdO分解为Pd,导致催化活性下降.PdO遇到含水或硫的化合物时会生成惰性的Pd(OH)2或稳定的硫化物,造成活性物种的流失,从而降低催化剂的性能.如果在材料中添加另一种贵金属Pt,使之与Pd一起形成贵金属合金,则可提高其低温催化燃烧的活性,增加Pd基催化剂的热稳定性以及抗水和抗硫能力.另一方面,过渡金属氧化物价格便宜,热稳定性以及抗硫性较好,也常作为甲烷燃烧的催化剂.其中三氧化二锰由于具有可变的氧化态以及较好的储氧能力受到了广泛关注.本课题组采用KIT-6作为硬模板,先合成具有有序介孔结构的Mn2O3(meso-Mn2O3)纳米催化剂,然后通过聚乙烯醇(PVA)保护的液相共还原法分别制备meso-Mn2O3担载Pd,Pt及PdPt合金的纳米催化剂(x(PdyPt)/meso-Mn2O3;x=(0.10-1.50)wt%;Pd/Pt摩尔比(y)=4.9-5.1).XRD结果表明,合成的meso-Mn2O3具有立方相晶体结构.其BET比表面积为106 m2/g.由TEM照片可观察到粒径范围为2.1?2.8 nm的贵金属纳米颗粒均匀分散在meso-Mn2O3表面.通过XPS分析可知,结合能在529.6和531.2 eV的峰可分别归属于晶格氧(Olat)和表面吸附氧(Oads).Pd0和Pd2+以及Pt0和Pt2+也均可通过曲线拟合后进行分峰确定.XPS定量分析结果表明,样品的Oads/Olat摩尔比有如下顺序:1.41(Pd5.1Pt)/meso-Mn2O3(0.77)>1.40Pd/meso-Mn2O3(0.69)>0.72(Pd5.1Pt)/meso-Mn2O3(0.65)>1.42Pt/meso-Mn2O3(0.63)>0.07(Pd4.9Pt)/meso-Mn2O3(0.53)>0.07(Pd4.9Pt)/bulk-Mn2O3(0.52)>meso-Mn2O3(0.45),这与其催化活性的顺序一相致.该结果表明,高的吸附氧物种浓度有利于甲烷催化燃烧.负载Pd,Pt或PdPt以后的样品的表面吸附氧物种浓度显著提高,催化活性最好的1.41(Pd5.1Pt)/meso-Mn2O3样品具有最高的吸附氧物种浓度.负载PdPt合金可有效提高催化剂对甲烷燃烧的催化活性.1.41(Pd5.1Pt)/meso-Mn2O3催化剂的活性最好:在空速为20000 mL/(g.h)的条件下,甲烷燃烧的T10%,T50%和T90%分别为265,345和425oC.此外,还考察了引入一定量的SO2,CO2,H2O和NO对甲烷在1.41(Pd5.1Pt)/meso-Mn2O3催化剂上氧化反应的影响,发现引入少量的Pt可提高催化剂抗SO2,CO2和H2O的能力,但是NO对甲烷燃烧的还原效应也不可忽视.基于催化剂物化性质的表征结果和活性数据,我们认为1.41(Pd5.1Pt)/meso-Mn2O3优异的催化性能与其拥有高质量的三维有序多孔结构、高的吸附氧物种浓度、优良的低温还原性以及Pd-Pt合金与meso-Mn2O3载体之间的强相互作用有关.     

Surface-enhanced Raman scattering characteristics of 4-nitrobenzenethiol adsorbed on palladium and silver thin films

Palladium is an important catalytic metal, and it is desirable to develop a surface-enhanced Raman scattering (SERS) technique to investigate the reagent and product species adsorbed on its surface. Unfortunately, Pt-group metals, e.g., Pt and Pd, have been commonly considered as non- or weak-SERS-active substrates. In this work, Ag and Pd thin films were deposited very efficiently and evenly onto the surface of glass substrates by using only corresponding metal nitrate salts (AgNO₃ and Pd(NO₃)₂) with butylamine in ethanolic solutions. In this process, pure ethanol was used for Ag deposition, while an ethanol–water (8:2) mixture was used for Pd deposition. The as-prepared Ag and Pd films exhibited SERS activity over a large area. The surface-induced photoconversion capabilities of these Ag and Pd films were then tested on 4-nitrobenzenethiol by means of SERS. It was found that at least under visible laser irradiation, the surface-catalyzed photoreaction occurs more readily on a Ag film than on a Pd film for the conversion of 4-nitrobenzenethiol to 4-aminobenzenethiol, even though Pd is known to be an important transition metal with high catalytic activity.     

贵金属催化p-叔丁基-α-甲基肉桂醛加氢

采用傅里叶变换红外光谱仪(FT-IR)、N₂吸脱附、X射线衍射(XRD)、透射电子显微镜(TEM)揭示了微波辅助-KOH处理对活性炭的物理化学性能的影响规律。 结果表明,活性炭表面的含氧基团的种类增加,微孔明显减少,中大孔的比例增大。 通过浸渍-原位还原方法制备了Pt、Pd、Ru、Rh负载微波辅助-KOH处理活性炭催化剂,并对其催化p-叔丁基-α-甲基肉桂醛选择性加氢性能进行了研究。 发现Pt具有优异的C=O加氢选择性,而Pd具有优良的C=C加氢选择性。 进一步研究了Pd-Pt双组分催化剂催化p-叔丁基-α-甲基肉桂醛加氢产物分布,随着Pt含量的增加, C=O选择性逐步提高, C=C选择性逐渐下降,且当m(Pd)∶m(Pt)=4∶1时,其催化剂的催化性能最佳。     

溶胶-凝胶法制备薄膜型TiO2光催化剂

用TiCl4作原料,通过溶胶-凝胶法在单晶硅基片上制备了TiO2纳米薄膜,并用XRD,AES,XPS以及紫外反射光谱等手段,对TiO2薄膜的结构进行了研究.结果发现,TiO2薄膜以锐钛矿型晶相存在.TiO2薄膜层与硅衬底间无明显的界面扩散反应.掺杂的Pd在还原前的薄膜中以氧化态存在,还原后则以高分散的金属态存在.掺杂的Pt在还原前后均以金属态存在,但还原后产生颗粒聚集.掺杂Pd的TiO2薄膜经还原后,其紫外吸收强度明显提高,主吸收峰发生红移.     

Nanosized (mu12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x approximately 7) containing Pt-centered four-shell 165-atom Pd-Pt core with unprecedented intershell bridging carbonyl ligands: comparative analysis of icosahedral shell-growth patterns with geometrically related Pd145(CO)x(PEt3)30 (x approximately 60) containing capped three-shell Pd145 core

Presented herein are the preparation and crystallographic/microanalytical/magnetic/spectroscopic characterization of the Pt-centered four-shell 165-atom Pd-Pt cluster, (mu(12)-Pt)Pd(164-x)Pt(x)(CO)(72)(PPh(3))(20) (x approximately 7), 1, that replaces the geometrically related capped three-shell icosahedral Pd(145) cluster, Pd(145)(CO)(x)(PEt(3))(30) (x approximately 60), 2, as the largest crystallographically determined discrete transition metal cluster with direct metal-metal bonding. A detailed comparison of their shell-growth patterns gives rise to important stereochemical implications concerning completely unexpected structural dissimilarities as well as similarities and provides new insight concerning possible synthetic approaches for generation of multi-shell metal clusters. 1 was reproducibly prepared in small yields (<10%) from the reaction of Pd(10)(CO)(12)(PPh(3))(6) with Pt(CO)(2)(PPh(3))(2). Its 165-atom metal-core geometry and 20 PPh(3) and 72 CO ligands were established from a low-temperature (100 K) CCD X-ray diffraction study. The well-determined crystal structure is attributed largely to 1 possessing cubic T(h) (2/m3) site symmetry, which is the highest crystallographic subgroup of the noncrystallographic pseudo-icosahedral I(h) (2/m35) symmetry. The "full" four-shell Pd-Pt anatomy of 1 consists of: (a) shell 1 with the centered (mu(12)-Pt) atom encapsulated by the 12-atom icosahedral Pt(x)Pd(12-x) cage, x = 1.2(3); (b) shell 2 with the 42-atom nu(2) icosahedral Pt(x)Pd(42-x) cage, x = 3.5(5); (c) shell 3 with the anti-Mackay 60-atom semi-regular rhombicosidodecahedral Pt(x)Pd(60-x) cage, x = 2.2(6); (d) shell 4 with the 50-atom nu(2) pentagonal dodecahedral Pd(50) cage. The total number of crystallographically estimated Pt atoms, 8 +/- 3, which was obtained from least-squares (Pt(x)/Pd(1-x))-occupancy analysis of the X-ray data that conclusively revealed the central atom to be pure Pt (occupancy factor, x = 1.00(3)), is fortuitously in agreement with that of 7.6(7) found from an X-ray Pt/Pd microanalysis (WDS spectrometer) on three crystals of 1. Our utilization of this site-occupancy (Pt(x)Pd(1-x))-analysis for shells 1-3 originated from the microanalytical results; otherwise, the presumed metal-core composition would have been (mu(12)-Pt)Pd(164). [Alternatively, the (mu(12)-Pt)M(164) core-geometry of 1 may be viewed as a pseudo-Ih Pt-centered six-shell successive nu(1) polyhedral system, each with radially equivalent vertex atoms: Pt@M(12)(icosahedron)@M(30)(icosidodecahedron)@M(12)(icosahedron)@M(60)(rhombicosidodecahedron)@M(30)(icosidodecahedron)@M(20)(pentagonal dodecahedron)]. Completely surprising structural dissimilarities between 1 and 2 are: (1) to date 1 is only reproducibly isolated as a heterometallic Pd-Pt cluster with a central Pt instead of Pd atom; (2) the 50 atoms comprising the outer fourth nu(2) pentagonal dodecahedral shell in 1 are less than the 60 atoms of the inner third shell in 1, in contradistinction to shell-by-shell growth processes in all other known shell-based structures; (3) the 10 fewer PR3 ligands in 1 necessitate larger bulky PPh(3) ligands to protect the Pd-Pt core-geometry; (4) the 72 CO ligands consist of six bridging COs within each of the 12 pentagons in shell 4 that are coordinated to intershell metal atoms. SQUID magnetometry measurements showed a single-crystal sample of 1 to be diamagnetic over the entire temperature range of 10-300 K.     

枝晶状Pt 薄膜的制备及其特殊红外效应

采用方波电位, 在10×10^-3 mol·L^-1 K₂PtCl₆+3×10^-4 mol·L^-1 PbAc₂+0.5 mol·L^-1 HClO₄溶液中, 于本体Pt 电极上电沉积制备出枝晶状Pt 薄膜. 随着沉积时间的增加, 枝晶长度逐渐由400 nm增加到900 nm, 且枝晶上的小晶粒(~10 nm大小)变得密集. 根据循环伏安(CV)曲线中氢吸脱附电量可得出Pt 薄膜具有中等粗糙度(C_r=9-36), 且电极表面的粗糙度随着沉积时间增加而增大. 观察到Pt 薄膜上吸附态CO的原位红外光谱具有明显的增强吸收效应, 当沉积时间为6 min 时所制得的枝晶Pt 电极的红外增强效应最大. CO呈现多种谱峰形状, 随着沉积时间的增加, 谱峰形状依次为左高右低的双极峰(类Fano 红外效应), 单极向下(表面增强红外吸收), 左高右低的双极峰, 单极向上(异常红外效应), 左低右高的双极峰和单极向下. 这表明纳米材料薄膜所呈现出的特殊红外性能, 与纳米材料的尺度和聚集状态等密切相关. 所制备的枝晶状Pt 薄膜有望为深入认识纳米材料的特殊红外性能提供一个良好的模型材料.     

Nanocrystals composed of alternating shells of Pd and Pt can be obtained by sequentially adding different precursors

This paper describes a layer-by-layer epitaxial approach to the synthesis of multishelled nanocrystals composed of alternating shells of Pd and Pt by starting with seeds made of Pd or Pt nanocrystals. The synthesis was conducted by sequentially adding PtCl(4)(2-) and PdCl(4)(2-) salt precursors into a system containing either Pd or Pt seeds (in the shape of cuboctahedrons, octahedrons, plates, or cubes) together with a weak reducing agent such as citric acid (CA). The slow reduction kinetics associated with CA played an important role in the epitaxial growth of one metal on the other, resulting in the formation of Pd-Pt multishelled nanocrystals. Owing to the capping effect of CA for {111} facets of Pd and Pt, the multishelled nanocrystals tended to be enclosed by {111} facets in the form of octahedrons or thin plates, depending on the shapes of the Pd or Pt seeds: octahedrons for cuboctahedral, cubic, or octahedral seeds, and plates for platelike seeds.