原位红外研究Pd／Al_2O_3催化CO氧化反应

用原位红外技术研究了Ｐｄ／Ａｌ２Ｏ３催化ＣＯ氧化反应，对ＣＯ吸附态的特征以及ＣＯ氧化反应中ＣＯ和Ｏ２的配比进行了试验，获得Ｐｄ／Ａｌ２Ｏ３吸附多重谱带和它在２８５～３７３Ｋ温区范围内的变化情况。由此证明，Ｐｄ与Ａｌ２Ｏ３发生了相互作用。根据桥型谱带在ＣＯ和Ｏ２共吸附于不同温度时的变化，确定了转化反应较快的ＣＯ和Ｏ２配比为２：１。     

聚变燃料纯化用有支撑钯银合金选择渗氢膜的研制

采用脉冲电镀和多层镀膜技术制备了约８μｍ厚的ＰｄＡｇａｔ．％膜，底衬为φ５０的３１６不锈钢滤片。研究确定了组成单一均匀，结构稳定而且与基体结合牢固的有支撑钯银合金选择渗氢膜的热处理条件。对它的选择渗氢性能进行了考核。３５０℃时单位面积渗氢速率为商品ＰｄＡｇ２５ａｔ．％膜的９．１倍。含氦１５％的氢经过这种膜纯化后氦含量降为０．０３％，研究表明，有支撑钯银合金膜的渗氢性能和纯化效率均能满足我国聚变裂变     

PEI-GNs/PMo_(12)复合膜负载Pd对甲酸氧化催化性能研究

利用层层自组装法制备了PEI-GNs/PMo_(12)复合膜,以PEI-GNs/PMo_(12)复合膜为载体,利用电化学还原法制备了复合膜载Pd催化剂(Pd/PEI-GNs/PMo_(12))。运用X射线光电子能谱(XPS)、X射线粉末衍射(XRD)、扫描电镜(SEM)等对催化剂的组成、结构、形态进行表征,结果表明:实验成功制备了Pd/PEI-GNs/PMo_(12)催化剂,且Pd/PEI-GNs/PMo_(12)改善了Pd粒子的分散性。运用电化学方法考察了Pd/PEI-GNs/PMo_(12)对Pd纳米粒子电催化性能的影响,结果表明,相对于Pd催化剂,Pd/PEI-GNs/PMo_(12)催化剂表现出更高的催化活性和稳定性,这主要是由于Pd粒子在PEI-GNs/PMo_(12)载体上形成均匀分散的纳米粒子及PEI-GNs/PMo_(12)良好的电子传递能力。     

Bimetallic Pd-Ni core-shell nanoparticles as effective catalysts for the Suzuki reaction

A simple and efficient solution-based method for the synthesis of Pd-Ni bimetallic nanoparticles （NPs） has been developed. A series of Pd-Ni bimetallic NPs were readily achieved by reduction of PdC12 and Ni（acac）2 （acac = acetyl- acetonate） in the presence of oleylamine （OAm）, oleic acid （OA） and benzyl alcohol. Furthermore, by using high-resolution transmission electron microscopy （HRTEM）, energy-dispersive spectrometry （EDS） mapping and X-ray diffraction （XRD）, we demonstrate that the as-prepared Pd-Ni bimetallic NPs have core-shell structures with a Pd-rich core and a Ni-rich shell. In addition, the as-obtained Pd-Ni bimetallic NPs with varying compositions show excellent catalytic activities in the Miyaura-Suzuki reaction. When the nickel molar percentage was 0.23 to 0.65, the conversion with the as-obtained Pd-Ni bimetallic catalysts was above 90%. It is believed that this strategy can be employed to produce a variety of other well-defined core-shell type multimetallic nanostructures.     

Palladium dispersed multiwalled carbon nanotube based hydrogen sensor for fuel cell applications

Palladium nanocatalysts supported on surface-oxidized multiwalled carbon nanotubes (MWNT) were prepared by the aqueous solution reduction of _PdCl2${\mathrm{PdCl}}_2$. MWNT have been synthesized by catalytic chemical vapor deposition (CCVD) technique. Pyrolysis of acetylene using a fixed-bed catalytic reactor over rare earth (RE) based _AB2${\mathrm{AB}}_2$ alloy hydride catalyst, obtained through hydrogen decrepitation technique, has been performed to synthesize MWNT. Structural, morphological and vibrational characterizations have been carried out using XRD, SEM, TEM and Raman spectroscopy, respectively. In situ electrical resistance measurements for thin films of MWNT obtained by spin coating samples were carried out by two-probe technique in a chamber with provision to introduce known concentration of hydrogen in constant air flow. Investigations of hydrogen sensing properties of Pd–MWNT ensembles have been carried out. The stability of Pd–MWNT thin films after several cycles of adsorption and desorption was studied. The change in electrical resistance due to hydrogen adsorption is reversible, with increase to saturation on exposure to hydrogen gas. The results demonstrate that chemically treated MWNT functionalized with nanostructured Pd show good _H2${\mathrm{H}}_2$ sensing response at room temperature.     

Hydrogen from methanol steam-reforming over Cu-based catalysts with and without Pd promotion

The catalytic steam reforming of methanol has been investigated over Cu-based catalysts with and without Pd addition, and comparing with typical commercial catalysts. The most active commercial catalyst had an activity comparable to values reported in the literature. The effect of adding Pd to a CuZn catalyst was twofold. The initial start-up properties of the catalyst were improved, allowing a rapid attainment of the activity without any pre-reduction of the catalyst. However, the addition of Pd also led to poorer selectivity, due to a significant increase in the selectivity to CO.     

Radiation induced synthesis of Au-Pd nanoparticles of random alloy structure supported on carbon particles using the high energy electron beam

Au-Pd bimetallic nanoparticles supported on carbon particles were synthesized by reduction of precursor ions in an aqueous solution irradiated with a high energy electron beam. The composition of the samples was analyzed by the inductively coupled plasma atomic emission spectrometry (ICP-AES), and the morphology of the samples was observed by the transmission electron microscope (TEM). TEM micrographs indicated that Au-Pd particles of ca. 5-nm were well dispersed on the surface of carbon particles of ca. 30-nm without any serious agglomeration. Addition of citric acid to the initial solution and high pH were found to be effective for formation of random alloy structure in the resultant bimetallic nanoparticles. The change in the bimetallic structure from core-shell to random alloy was identified by techniques of the X-ray diffraction (XRD) and the extended X-ray absorption fine structure (EXAFS).     

Effect of various single metallic seed-layers on the magnetic properties of Co/Pd multilayers

We studied the effects of Pd, Ru, and Ta seed-layers on the perpendicular magnetic properties of Co/Pd multilayers, promising materials for high-density magnetic recording media. Among the various seeds, the Ta seed-layer demonstrated a large coercivity and most highly promoted fcc (111) preferred orientation of the Co/Pd multilayer. We also patterned films into island arrays with sizes of 2 × 2 μm², 5 × 5 μm², and 10 × 10 μm² to investigate the effect of size on the magnetic properties. The coercivity increased as the island size decreased. The 2 × 2 μm² patterned Co/Pd multilayer with the Ta seed-layer showed a coercivity about six times greater than that of the un-patterned film. This increase can be explained by a change in the magnetization reversal mechanism from domain wall propagation to domain rotation.