掺杂Fe元素对Pd/C催化剂性能的影响

用Fe作为掺杂元素, 以活性炭为载体, 通过浸渍还原方法制备了Pd:Fe原子比分别为1:1、2:1、1:2的Pd-Fe/C催化剂.采用TEM和XRD技术对合金催化剂的物理性质进行了测试. 结果表明, 获得的Pd-Fe/C催化剂合金粒子在载体上分布均匀, 粒径<5nm,Fe的掺杂量对Pd/C催化剂晶体结构有很大影响, 通过电化学性能测试比较, 分析了三个不同比例的Pd-Fe/C催化剂和Pd/C催化剂对氢和甲酸的电催化氧化性能. 结果得出:在相同的峰值电位下, 几种催化剂的电流密度大小顺序为: Pd-Fe/C(1:1)>Pd-Fe/C(2:1)>Pd/C>Pd-Fe/C(1:2). 结果表明, 适量掺杂Fe提高了Pd/C催化剂的催化性能, 且Pd:Fe原子比为1:1时催化性能最好.     

Pdn-Fe纳米合金作为Mg-H2O2半燃料电池阴极研究

通过化学还原方法制备Pd:Fe原子比(n)为2 : 1、4 : 1、8 : 1的Pd_n-Fe/C催化剂。采用TEM、XRD和XPS技术对复合催化剂进行表征。结果显示, Fe加入Pd/C催化剂中, 与Pd形成合金, Pd_n-Fe/C催化剂的粒径发生变化; 获得的Pd₄-Fe纳米合金粒子在C载体表面分布均匀, 平均粒径为2~3 nm, Fe的加入对Pd/C催化剂晶体结构有很大影响。电化学(CV, LSV, CA)测试表明: 加入Fe提高了Pd/C催化剂的催化性能, Pd/Fe原子比为4 : 1时, Pd_n-Fe/C的催化性能最好。当E=0.2 V时, Pd/C电极电流密度为17.71 mA/cm², 而Pd₄-Fe/C电极电流密度可达19.42 mA/cm²。电池测试表明, 以Pd₄-Fe/C和Pd/C催化剂为阴极的Mg-H₂O₂半燃料电池的开路电势均为1.8 V左右, 而当电流密度为180 mA/cm²时, 以Pd₄-Fe/C为阴极的电池最大能量密度比Pd/C为阴极的电池高41 mW/cm²。     

铂、钯材料ICP分析方法的研究

由于铂、钯材料被广泛应用于多种精密行业,其材料含量也越来越受到重视,目前采用的方法不是操作复杂就是范围太窄而不符合日常检测要求,因此急需建立一种简捷快速的、适用于铂、钯材料含量为95．0％-99．99％的化学分析方法。该文用电感耦合等离子发射光谱分析,测定铂、钯材料中铂（钯）、铑、铱、钌、金、银、铜、铁、镍、铝、铅、锰、铬、镁、锡、硅、锌及铋等杂质元素的方法,达到了检出限低、重复性好、回收率在88．3％-100％的检测目标。     

Facile one-pot synthesis of superfine palladium nanoparticles on polydopamine-functionalized carbon nanotubes as a nanocatalyst for the Heck reaction

Heterogeneous Pd nanocatalysts are efficient catalysts for the Heck reaction but require multi-step,sophisticated procedures and harsh reaction conditions.In this work,a green and facile strategy has been developed to decorate Pd nanoparticles on polydopamine(PDA)-coated multi-walled carbon nano-tubes(Pd/CNTs-PDA)via a one-pot method.The obtained nanoparticles were characterized by various techniques including transmission electron microscopy,X-ray diffraction,and X-ray photoelectron spec-troscopy,which proved that Pd NPs are well-dispersed on the PDA and between the surfaces of the PDA and CNTs.The resultant Pd/CNTs-PDA catalysts exhibit excellent catalytic reactivity toward the Heck reaction at low temperatures.Moreover,by DFT simulation,we found that during the PDA polymeriza-tion process,a large number of unsaturated-N=and C=O species are more active than the groups on the PDA end product to anchor Pd NPs.The results provide evidence that the catalyst synthesized by the one-pot method exhibited good activity because sufficient active sites could be created to effectively promote Pd NPs dispersion during the dopamine polymerization process.Additionally,the Pd/CNTs-PDA catalyst was successfully employed in Heck cross-coupling reactions with various functionalized substrates.This method opens a window for the fabrication of high-performance nanocomposite catalysts under mild conditions using simple methods and has several potential applications.     

Construction and Investigation of Pt/Pd Thermocouples in the Framework of the Euromet Project 857

The objective of the EUROMET Project 857 in the field of thermometry, “High-temperature fixed points for improved thermocouple calibrations,” is the development of robust high-temperature fixed points based on metal-carbon eutectic alloys for the calibration of thermocouples above 1,084°C. This paper describes the construction and investigation of Pt/Pd thermocouples to be used to compare different cobalt–carbon (Co–C) fixed-point cells constructed by the three participants of this project. A set of three Pt/Pd thermocouples was prepared by PTB and NPL and a set of four by LNE. Their metrological performances in terms of thermoelectric stability and homogeneity were assessed in different ways. The results of these investigations, as well as the results of first measurements of local Co–C eutectic fixed-point cells by using Pt/Pd thermocouples, are presented.     

Carbon nanotube formation over laser ablated M and M/Pd (M = Fe,Co, Ni) catalysts: The effect of Pd addition

Monometallic and bimetallic M and M/Pd (M = Fe, Co, Ni) nanoparticles were prepared by pulsed Nd:YAG laser ablation of bulk M and Pd targets in acetone and transferred onto Si wafers to catalyze carbon nanotubes from decomposition of liquid petroleum gas via thermal chemical vapor deposition at 750°C. Transmission electron microscopy and optical extinction study revealed that the prepared M and M/Pd nanoparticles have rather spherical shape and their aspect ratios are nearly one. In comparison to monometallic M catalysts by addition of Pd, the average sizes of produced bimetallic M/Pd catalysts increased. Carbon nanotubes' characterization revealed that by addition of Pd to laser ablated M catalysts the average diameter, the yield, and quality of end product carbon nanotubes were increased. The average diameter of grown carbon nanotubes increases as: Ni < Ni/Pd < Co < Co/Pd < Fe < Fe/Pd and the quality of them increases as: Ni < Co < Fe < Ni/Pd < Fe/Pd < Co/Pd.     

炔基化改性聚乙烯醇吸氢材料的制备及吸氢性能表征

以聚乙烯醇(PVA)高分子材料为基体,通过氨基甲酸酯化反应在PVA高分子链上引入炔基形成炔基功能化的高分子,利用核磁共振法对炔基化高分子的分子结构及接枝度进行表征。通过化学还原法制备出炔基化高分子负载纳米钯的复合材料,采用激光粒度仪确定纳米钯粒径分布。同时将不同接枝度炔基功能化的PVA和Pd/C催化剂,按照一定的比例采用研磨法制备出吸氢材料。利用PVT法对上述所有的吸氢材料的吸氢性能进行了研究。结果表明,氨基甲酸酯化改性PVA接枝度高的炔基化高分子与Pd/C混合研磨后的吸氢材料的吸氢效果最好,吸氢容量为0.8893 mol/kg。     

Pd embedded in porous carbon （Pd@CMK-3） as an active catalyst for Suzuki reactions： Accelerating mass transfer to enhance the reaction rate

Heterogeneous catalysts are promising candidates for use in organic reactions due to their advantages in separation, recovery, and environment compatibility. In this work, an active porous catalyst denoted as Pd embedded in porous carbon （Pd@CMK-3） has been prepared by a strategy involving immersion, ammonia- hydrolysis, and heating procedures. Detailed characterization of the catalyst revealed that Pd（0） and Pd（I1） species co-exist and were embedded in the matrix of the porous carbon （CMK-3）. The as-prepared catalyst has shown high activity toward Suzuki reactions. Importantly, if the reaction mixture was homogenized by two minutes of ultrasonication rather than magnetic stirring before heating, the resistance to mass transfer in the pore channels was significantly reduced. As a result, the reactions proceeded more rapidly and a four-fold increase in the turnover frequency （TOF） could be obtained. When the ultrasonication was employed throughout the entire reaction process, the conversion could also exceed 90% even without the protection of inert gas, and although the reaction temperature was lowered to 30 ℃. This work provides a method for fabricating highly active porous carbon encapsulated Pd catalysts for Suzuki reactions and proves that the problem of mass transfer in porous catalysts can be conveniently resolved by ultrasonication without any chemical modification being necessary.     

碱性介质中Pd/Sn石墨电极的电催化性能

采用化学镀制备了Pd/Sn石墨电极,用扫描电子显微镜观察了改性后石墨电极试样的微观组织,用能谱仪确定石墨电极的表面成分,用循环伏安法及电化学阻抗研究了石墨电极的甲醇氧化电催化性能.结果表明,Pd/Sn以球状颗粒存在于石墨电极表面,没有出现明显的团聚.峰电流密度与电势扫描速率平方根呈线性关系,电极上甲醇氧化和中间产物氧化...     

标准铂铑10-铂热电偶热电势约束公式探讨

铂铑10-铂热电偶可以通过3个固定点的热电势与温度之间的关系反映其特性。在ITPS-68温标中,铂铑10-铂热电偶作为温标内插仪器,其3个固定点热电势必须满足一定的约束公式。介绍了从其约束公式推导出现行检定规程使用的3个不同的温度固定点的新约束公式,以规范标准铂铑10-铂热电偶的热电特性;通过对大量源于中国计量科学研究院热电偶校准实验室的标准热电偶的实际数据的计算,验证了新约束公式的有效性。新公式在锌固定点的不合格检出率从0% 提升到3%左右。     

Co-Firing Characteristics of Cordierite Tapes with Ag/Pd for High Frequency Chip Inductors

As a new electronic material, low-temperature sintering, low-dielectric cordierite tapes exhibit great potential in the manufacturing of high frequency inductors. While the co-firing of cordierite dielectric material with conductive metal in lower sintering temperature is always a difficulty, and it directly affects the practical application of the inductors. In this paper, the prepared cordierite tapes with low-sintering temperature, low dielectric constant, and low losses were used as matrix material, and the co-firing characteristics of cordierite tapes with Ag/Pd was preliminary studied to investigate the feasibility in the manufacturing process. Deformation, pores, and delaminations are three main defects of the co-fired samples. With an Al₂O₃ powders and press blocks assisted process, good co-firing effect of cordierite tapes with Ag/Pd can be obtained at 900 °C. The co-firing interface of cordierite tape and Ag/Pd is very dense and no obvious element migration is detected. The paper is contributed to the manufacture of high frequency inductors.     

Enhancing both selectivity and coking-resistance of a single-atom Pd<Subscript>1</Subscript>/C<Subscript>3</Subscript>N<Subscript>4</Subscript> catalyst for acetylene hydrogenation

Selective hydrogenation is an important industrial catalytic process in chemical upgrading,where Pd-based catalysts are widely used because of their high hydrogenation activities.However,poor selectivity and short catalyst lifetime because of heavy coke formation have been major concerns.In this work,atomically dispersed Pd atoms were successfully synthesized on graphitic carbon nitride (g-C3N4) using atomic layer deposition.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) confirmed the dominant presence of isolated Pd atoms without Pd nanoparticle (NP) formation.During selective hydrogenation of acetylene in excess ethylene,the g-C3N4-supported Pd NP catalysts had strikingly higher ethylene selectivities than the conventional Pd/A12O3 and Pd/SiO2 catalysts.In-situ X-ray photoemission spectroscopy revealed that the considerable charge transfer from the Pd NPs to g-C3N4 likely plays an important role in the catalytic performance enhancement.More impressively,the single-atom Pd1/C3N4 catalyst exhibited both higher ethylene selectivity and higher coking resistance.Our work demonstrates that the single-atom Pd catalyst is a promising candidate for improving both selectivity and coking-resistance in hydrogenation reactions.     

Perforated Pd Nanosheets with Crystalline/Amorphous Heterostructures as a Highly Active Robust Catalyst toward Formic Acid Oxidation

Perforated ultrathin Pd nanosheets with crystalline/amorphous heterostructures are rationally synthesized to offer a large electrochemically active surface area of 172.6 m² g^?1 and deliver a 5.6 times higher apparent reaction rate in comparison to commercial Pd/C, thus offering a facile confined growth method to generate superior catalysts.     

A stepwise-designed Rh-Au-Si nanocomposite that surpasses Pt/C hydrogen evolution activity at high overpotentials

Hydrogen evolution by electrocatalysis is an attractive method of supplying clean energy.However,it is challenging to find cheap and efficient alternatives to rare and expensive platinum based catalysts.Pt provides the best hydrogen evolution performance,because it optimally balances the free energies of adsorption and desorption.Appropriate control of these quantities is essential for producing an efficient electrocatalyst.We demonstrate,based on first principles calculations,a stepwise designed Rh-Au-Si ternary catalyst,in which adsorption (the Volmer reaction) and desorption (the Heyrovsky reaction) take place on Rh and Si surfaces,respectively.The intermediate Au surface plays a vital role by promoting hydrogen diffusion from the Rh to the Si surface.Theoretical predictions have been explored extensively and verified by experimental observations.The optimized catalyst (Rh-Au-SiNW-2) has a composition of 2.2∶28.5∶69.3 (Rh∶Au∶Si mass ratio) and exhibits a Tafel slope of 24.0 mV·dec-1.Its electrocatalytic activity surpasses that of a commercial 40 wt.％ Pt/C catalyst at overpotentials above 0.19 V by exhibiting a current density of greater than 108 mA·cm-2.At 0.3 V overpotential,the turnover frequency of Rh-Au-SiNW-2 is 10.8 times greater than that of 40 wt.％ Pt/C.These properties may open new directions in the stepwise design of highly efficient catalysts for the hydrogen evolution reaction (HER).     

Pt/C催化剂制备及CO催化氧化性能研究

采用大气压介质阻挡放电辅助氢气热还原方法和氢气热还原方法制备Pt/C催化剂,考察了制备方法及Pt负载量对Pt/C催化性能的影响。采用X-射线衍射(XRD)、循环伏安法、CO催化氧化反应研究Pt/C催化剂的晶相结构、电催化性能和CO催化氧化活性。结果表明:大气压介质阻挡放电辅助氢气热还原所制备的样品具有更高的电化学活性和CO催化氧化活性。当Pt负载量在2%到10%之间变化时,Pt/C-PC催化活性随负载量增加而增加。XRD测试结果显示当Pt负载量为2%,5%和10%时,Pt粒径分别为:10.6 nm,9.1 nm和6.4 nm,说明采用等离子体辅助氢气热还原方法制备的Pt/C-PC催化剂,Pt负载量越大,Pt粒径越小,CO催化氧化活性更高。     

Simultaneous Contact and Non-contact Measurements of the Melting Temperature of a Ni–C Fixed-Point Cell

A novel fixed-point cell design that allows simultaneous measurements using contact and non-contact thermometers was developed and investigated at PTB to realize the nickel-carbon (Ni–C) fixed-point. The melting temperature indicated by the LP3 radiation thermometer amounted to (1328.86 ± 0.52)°C (k = 2). The melting temperature of the Ni–C fixed-point cell was also calculated by extrapolating the emf-temperature characteristics of two Pt/Pd thermocouples based on their calibrations at conventional fixed points of the ITS-90. The melting temperature of the Ni–C eutectic amounts to (1328.44 ± 0.45)°C using thermocouple Pt/Pd 01/04, and to (1328.53 ± 0.46)°C using thermocouple Pt/Pd 01/05, with uncertainties for k = 2. The contact and non-contact thermometers agree well within the combined uncertainties.     

Characterisation of nanolayered aluminium/palladium thin films using nanoindentation

Structure, hardness, and elastic modulus of nanolayered aluminium/palladium thin films, with individual layer thickness varying from 1 nm to 40 nm, were investigated using transmission electron microscopy (TEM) and nanoindentation. TEM micrographs indicated a sharp but not flat Al-Pd interface. With just 6.5% (v/v) Pd a hardness enhancement of ~ 200% was observed for nanolayered Al/Pd compared to the hardness of pure Al film. A maximum hardness enhancement of up to 350% was observed for nanolayered Al/Pd samples compared to the hardness of pure Al film when bilayer thickness was 2 nm and Pd was 50% (v/v). Modulus enhancement was also observed for the nanolayered thin films.     

笼状PAMAM模板纳米钯催化Suzuki反应

针对PAMAM模板纳米钯催化剂在循环使用中容易团聚产生钯黑的问题,文章利用4．5代PAMAM端基的酯基团与乙二胺反应形成鸟笼状大分子,以其为模版合成纳米钯催化剂,研究发现,当端基连接50％,反应条件温和,催化剂易于分离,循环使用4次,仍能保持70％的收率。     

Structure characterization of Pd/Co/Pd tri-layer films epitaxially grown on MgO single-crystal substrates

Pd/Co/Pd tri-layer films were prepared on MgO substrates of (001), (111), and (011) orientations at room temperature by ultra high vacuum rf magnetron sputtering. The detailed film structures around the Co/Pd and the Pd/Co interfaces are investigated by reflection high energy electron diffraction. Pd layers of (001)_fcc, (111)_fcc, and (011)_fcc orientations epitaxially grow on the respective MgO substrates. Strained fcc-Co(001) single-crystal layers are formed on the Pd(001)_fcc layers by accommodating the fairly large lattice mismatch between the Co and the Pd layers. On the Co layers,, Pd polycrystalline layers are formed. When Co films are formed on the Pd(111)_fcc and the Pd(011)_fcc layers, atomic mixing is observed around the Co/Pd interfaces and fcc-CoPd alloy phases are coexisting with Co crystals. The Co crystals formed on the Pd(111)_fcc layers consist of hcp(0001) + fcc(111) and Pd(111)_fcc epitaxial layers are formed on the Co layers. Co crystals epitaxially grow on the Pd(011)_fcc layers with two variants, hcp(11?00) and fcc(111). On the Co layers, Pd(011)_fcc epitaxial layers are formed.     

Catalytic stepwise nitrate hydrogenation in batch-recycle fixed-bed reactors

Pd (1.0 wt.%)-Cu (0.3 wt.%) bimetallic and Pd (1.0 wt.%) monometallic catalysts were synthesized by means of incipient-wetness impregnation technique and deposited on alumina spheres (dp=1.7 mm). The prepared catalysts were tested at T=298 K and p(H2)=1.0 bar in the integrated process of catalytic liquid-phase hydrogenation of aqueous nitrate solutions, in which the denitration step was carried out consecutively in separate, single-flow fixed-bed reactor units operating in a batch-recycle mode. In the first reactor packed with a Pd-Cu bimetallic catalyst, nitrate ions were transformed to nitrites at pH 12.5 with a selectivity as high as 93%; the rest was found in the form of ammonium ions. Liquid-phase nitrite hydrogenation to nitrogen in the second reactor unit packed with a Pd monometallic catalyst was conducted at low pH values of 3.7 and 4.5, respectively. Although these values are well below the pHpzc of examined catalyst (6.1), which assured that the nitrite reduction was carried out over a positively charged catalyst surface, up to 15% (23% in the presence of 5.0 g/l NaCl in the solution) of initial nitrite content was converted to undesired ammonium ions. Since a negligible amount of these species (below 0.5mg/l) was produced at identical operating conditions over a powdered Pd/gamma-Al2O3 catalyst, it is believed that the enhanced production of ammonium ions observed in the second fixed-bed reactor is due to the build-up of pH gradients in liquid-filled pores of spherical catalyst particles. Both Pd-Cu bimetallic and Pd monometallic catalysts were chemically resistant in the investigated range of pH values.