插层还原法制备纳米钯/石墨烯复合材料的研究

以氧化石墨和氯化双乙二胺钯Pd(en)2Cl2为前驱体,将金属钯前驱体与氧化石墨发生插层反应,再将插层了Pd(en)2+2的氧化石墨在溶液中用NaBH4还原,制备出纳米钯/石墨烯复合材料。采用X射线衍射(XRD)、场扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、电感耦合等离子体发射光谱(ICP)、低温氮气吸附等手段对复合材料进行表征并对复合材料进行了储氢性能的测试。研究结果表明:复合材料具有规则的中孔结构,直径为2~6 nm钯的纳米粒子弥散地分布在石墨烯的层间,起着支撑作用,阻止石墨烯片层的重新聚集;复合材料具有较高的BET比表面积,在77 K及0.11 MPa条件下其储氢量达到了3.4%(质量分数)。     

水浴法制备钯纳米颗粒及其修饰电极的电催化性能

利用Keggin结构的12-硅钨酸作为模板,采用水浴法还原硝酸钯制备了纳米钯.用透射电子显微镜(TEM)和X射线衍射(XRD)等手段对制备的钯纳米颗粒的形貌、粒径大小和结构进行了表征.利用滴涂法将Pd纳米颗粒修饰到Au电极表面,通过循环伏安法,研究了纳米Pd对肼的电催化性质.结果显示,制备的纳米钯为3～4 nm的类球形颗粒,为面心立方结构.纳米Pd修饰电极对肼具有良好的电催化氧化作用.在pH=6时,氧化峰电流(lpa)与肼的浓度呈现良好的线性关系.     

一种无铼二代镍基单晶高温合金蠕变机制研究

利用层层静电自组装技术将聚乙烯亚胺(PEI-Ag+)、PdCl42-交替沉积在基底上,然后用硼氢化钠还原,构筑了含银/钯复合纳米粒子的PEI-Ag/Pd纳米复合薄膜.通过扫描电子显微镜(FESEM),X射线光电子能谱(XPS)和循环伏安(CV)等手段对复合膜的成分、微结构和性质进行了测试分析.膜上生成了不规则和立方体状的银/钯纳米复合物,导致膜表面有一定的粗糙度.结果表明,双金属{PEI-Ag/Pd}n复合膜比单金属{PEI/Pd}n或{PEI-Ag/PSS}n膜对多巴胺的氧化有更好的电催化活性.     

Pdx-Co/C催化甲酸的电氧化性能研究

以活性碳(Vulcan XC-72)为载体,用化学还原法制备了不同Pd/Co摩尔比的Pdx-Co/C催化剂。用透射电镜(TEM)、X射线衍射(XRD)及X射线光电子能谱(XPS)对催化剂进行了表征,采用循环伏安法考察了催化剂对甲酸电氧化反应的催化性能。结果表明,Pdx-Co复合催化剂粒子均匀分散在碳载体表面;催化剂中掺入的少量Co元素部分进入Pd晶格,形成了Pd-Co合金;随着Pd/Co摩尔比的增加,Pd颗粒粒径先增大后减小,催化活性也表现出相同的变化趋势;当Pd:Co=8:1时,所得Pd8-Co/C对甲酸氧化的催化活性最高,峰电流密度可达到15.907 mA/cm²。     

改性Pd/USY分子筛的甲苯吸脱附性能研究

制备了载钯的超稳Y型(USY)分子筛材料Pd/USY,并组合其它贱金属进行改性,得到系列二元与多元改性Pd/USY;利用N_2物理吸附仪、高分辨透射电子显微镜(TEM)、热重分析(TG)仪、化学吸附仪和X射线衍射(XRD)仪等,表征分析了系列改性Pd/USY分子筛对甲苯的吸附与脱附性能。结果表明,改性后的Pd-Ce-Zr/USY分子筛吸附性能最好,甲苯饱和吸附量高达290.7 mg/g,甲苯高温脱附温度范围为290～360℃,其最佳改性条件为钯负载质量分数为1%,pH值调节至8,煅烧温度为450℃。     

阳极氧化Ti_3SiC_2制备纳米孔阵列EI北大核心CSCD

以NH4F和乙二醇为电解液,采用阳极氧化法在Ti_3SiC_2表面制备纳米多孔结构,研究阳极氧化电压、电解液浓度和氧化时间对纳米多孔结构形成的影响。利用场发射扫描电子显微镜(FE-SEM)、X射线衍射仪(XRD)和X射线光电子能谱(XPS)对纳米多孔结构进行表征。结果表明:孔径随着氧化电压的升高而增大,且延长氧化时间有利于制备孔径均匀的纳米孔;Ti_3SiC_2试样经阳极氧化后除含有Ti、Si、C元素外,还含有O元素,且以TiO_2的形态存在。     

碳纳米钯的生物合成及其催化性能研究

将奥奈达希瓦氏菌(S. oneidensis MR-1)原位还原形成的零价纳米钯颗粒负载在碳纳米管(CNTs)表面,制备了Pd/CNTs纳米复合材料。用TEM、XPS等多种手段对材料进行了表征,并用对硝基苯酚(4-NP)的还原降解反应评价了Pd/CNTs的催化性能。表征结果表明,钯纳米颗粒(直径2~3 nm)较均匀地分散在CNTs表面;钯负载在CNTs上会造成其拉曼峰强的增大和特征峰的偏移,且结晶度和颗粒数目随着负载量的增加而增加。性能评价表明,Pd/CNTs对4-NP还原降解具有较高催化性能,较其催化效率较单一的CNTs降解效率提高了6.3倍;在pH = 10的条件下,5% Pd/CNTs催化18 min可将4-NP降解99.5%,经6个反应循环后对4-NP的去除率仍保持在95.2%。     

阳极氧化Ti_3SiC_2制备纳米孔阵列

以NH4F和乙二醇为电解液,采用阳极氧化法在Ti_3SiC_2表面制备纳米多孔结构,研究阳极氧化电压、电解液浓度和氧化时间对纳米多孔结构形成的影响。利用场发射扫描电子显微镜(FE-SEM)、X射线衍射仪(XRD)和X射线光电子能谱(XPS)对纳米多孔结构进行表征。结果表明:孔径随着氧化电压的升高而增大,且延长氧化时间有利于制备孔径均匀的纳米孔;Ti_3SiC_2试样经阳极氧化后除含有Ti、Si、C元素外,还含有O元素,且以TiO_2的形态存在。     

绿色合成AMA反应中纳米Pd/C催化剂的失活和再生

在2-硝基-4-乙酰胺基苯甲醚(NMA)催化加氢合成2-氨基-4-乙酰胺基苯甲醚(AMA)反应中,规整纳米Pd/C催化剂表现出很好的催化活性和选择性。但Pd/C催化剂在反应的套用过程中表现出反应活性逐渐降低。通过XRD、BET、EDS、XPS等物性表征以及Na2S滴定法和原子吸收法测定Pd含量的研究表明,钯微晶的长大、钯流失、催化剂中毒等不是引起Pd/C催化剂失活的主要原因,而Pd/C催化剂表面金属钯活性位在反应后被2-氨基-4-乙酰胺基苯甲醚产物等有机物覆盖可能是导致其性能逐渐降低的关键。使用酸洗法可以去除反应后Pd/C催化剂表面覆盖的2-氨基-4-乙酰胺基苯甲醚等有机物,释放金属钯活性位,实现Pd/C催化剂的性能有较大程度的恢复;而其他方法对Pd/C催化剂活性恢复的效果不明显。     

防X射线稀土/聚丙烯复合纤维的制备及性能研究

通过密炼机将纳米稀土和聚丙烯(PP)共混,然后对共混物进行熔融纺丝,采用红外、差示扫描量热、X射线衍射、扫描电子显微镜测试等手段对所得纤维进行结构性能表征,并将短纤维层压作防辐射测试。实验结果表明,氧化镧质量分数在60%以内,其在聚丙烯基体中呈纳米级不均匀分散;随着氧化镧加入量的增加,铅当量也相应增加,稀土/聚丙烯复合防护纤维具有较好的X射线防护功能。     

Electrocatalytic performance of Pd–Ni nanowire arrays electrode for methanol electrooxidation in alkaline media

A successful approach to prepare the Pd–Ni nanowire arrays electrode without carbon supports was reported. The morphology and crystallinity of nanowire were characterized by transmission electron microscopy, selected-area electron diffraction(SAED), X-ray diffraction(XRD), and X-ray photoelectron spectroscopy(XPS) analyses, respectively. The results show that the diameters of the nanowire are in the range of 65–75 nm, and the polycrystalline binary solid solution alloy is formed in the Pd–Ni nanowire. Cyclic voltammograms, chronoamperograms, and electrochemical impedance spectroscopy demonstrate that the Pd–Ni nanowire arrays electrodes show excellent electrocatalytic performance for methanol oxidation in alkaline media. The catalytic activity of Pd–Ni nanowire arrays electrode is *1.39 times higher than that of the Pd nanowire arrays electrode and *2.28 times higher than that of the commercial Pd/C catalyst. This is mostly owing to the transfer of electron density from Ni to Pd. These results indicate that Pd–Ni nanowire arrays electrode is very promising in an alkaline direct methanol fuel cell.     

Multicomponent nanoporous metals prepared by dealloying Pd80−xNixP20 metallic glasses

We report the formation of Pd-based multicomponent nanoporous metals by electrochemically dealloying the Pd_80−xNi_xP₂₀ metallic glasses. It was found that both the compositions and the pore sizes of the nanoporous metals can be tailored by the Ni content in the glassy Pd_80−xNi_xP₂₀ precursors. Moreover, the Pd-based nanoporous metal with the optimized composition and the pore size exhibits better electrocatalytic performance towards the oxidation of the formic acid when compared with the commercial Pd/C catalyst.     

SiC 涂层对不同碳基体氧化防护行为的研究

为了提高碳材料的抗氧化性能,采用料浆烧结法在石墨和C/C复合材料上制备了SiC 抗氧化涂层.测试了SiC涂层在1200℃的高温下对不同碳基体的氧化防护能力,利用扫描电子显微镜 (SEM)、X-射线衍射仪(XRD)对涂层结构进行分析.结果表明:SiC涂层对不同碳材料的抗氧化防护行为有很大差异,在1200℃的高温下SiC涂层对石墨具有较好的抗氧化性能,而对C/C复合材料的氧化防护性能较差.     

Novel nanoporous palladium catalyst for electroreduction of hydrogen peroxide

Titanium-supported nanoporous palladium catalyst(Pd/Ti) was prepared by a hydrothermal method using PdCl2 as a precursor,ethylenediamine tetraacetic acid(EDTA) as a ligand,and formaldehyde as a reduction agent.Complex Pd-EDTA2-is favorable for the formation of Pd particles with nanoscale sizes.The electroactivity of the Pd/Ti catalyst towards the electroreduction of hydrogen peroxide in 1 mol/L NaOH solution was evaluated by voltammetric techniques.Both linear scan voltammetric and chronoamperometric data p...     

Multilayer oxidation protective coating for C/C composites from room temperature to 1500 °C

To prevent carbon/carbon (C/C) composites from oxidation, a multilayer oxidation resistant coating was prepared. The inner SiC coating was prepared by pack cementation, and the outer SiC-MoSi₂ three-layer coating was obtained by slurry coating using silicon-sol as the caking agent. X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to analyze the phase, microstructure and element distribution of the as-prepared coating. The results show that, the as-received multilayer coating has a crack-free structure with the thickness of about 300 μm. It is provided with excellent oxidation resistance from room temperature to 1500 °C in air and can protect C/C composites from oxidation for more than 120 h at 900 °C and more than 110 h at 1500 °C in air. The weight loss of the coated samples during oxidation tests mainly resulted from the oxidation of Mo₅Si₃ and the volatilization of SiO₂ in the coating.     

BaO对单Pd催化剂净化甲醇燃料车尾气性能的影响

利用FIB/SEM切片、XRD、TEM和EDX、EELS等先进分析技术对微球模板法所制备的Au/Ag泡沫材料的微观结构、形貌、成分及成分分布等进行了细致的研究.结果表明:由微球状Au/Ag球壳堆积而成的泡沫材料中微球直径约8 μm,微球壁厚200～1200 nm; Au/Ag泡沫材料的球壳可细分为3层,内层和外层为Au/Ag合金的微粒,中间主要是非晶碳层,夹杂有少量的Au/Ag微粒;Au/Ag泡沫材料的骨架由单个空心球壳组成,球壳之间通过接触点的金属镀层连接在一起;球壳上有小孔状结构,是在热分解法去除聚苯乙烯微球模板对形成的;球壳壁厚分布不均匀,少数球壳有塌陷、变形、破裂等现象.这些详细的分析有助于改进工艺,提高Au/Ag泡沫材料的制备质量.     

碱性条件下M/C(M=Pt, Pd, Ni, Ag, Au)对甲醇氧化电催化活性的对比研究

用化学还原法制备了M/C(M=Pt, Pd, Ni, Ag, Au) 5种纳米金属碳截催化剂,用XRD、XPS分别表征活性物的晶相结构、表面组成和价态形式,用TEM观察催化剂微观形貌,用循环伏安法测定不同催化剂对甲醇氧化的电催化活性。结果表明,催化剂中的纳米金属粒径在3~11 nm之间,纯度较高,在载体表面的分布较为均匀;Pd/C催化剂对甲醇氧化有较好的催化作用,Ni/C对甲醇氧化有一定的活性,而Ag/C和Au/C几乎没有活性。在1 mol·L-1CH3OH+1 mol·L-1NaOH条件下,Pd/C对甲醇氧化最高峰电流密度为890 mA·mg-1,约为Pt/C的66%,Ni/C对甲醇氧化最高峰电流密度为6.3 mA·mg-1,仅为Pt/C的0.46%。     

Facile synthesis of 3D nanoporous Pd/Co2O3 composites with enhanced catalytic performance for methanol oxidation

To simultaneously reduce noble metal Pd usage and enhance electrocatalytic performance for methanol oxidation, Pd/Co₂O₃ composites with ultrafine three-dimensional (3D) nanoporous structures were designed and synthesized by simple one-step dealloying of a melt-spun Al-Pd-Co alloy with an alkaline solution. Their electrocatalytic activity in alkaline media was determined by a Versa-STAT MC workstation. The results indicate that the typical sizes of the ligaments and pores of the composites were approximately 8–9 nm. The Co₂O₃ was uniformly distributed on the Pd ligament surface. Among the as-prepared samples, the nanoporous Pd/Co₂O₃ composite generated from dealloying of the Al_84.5Pd₁₅Co_0.5 alloy had the best electrocatalytic activity, and its activity was enhanced by approximately 230% compared with the nanoporous Pd from dealloying of Al₈₅Pd₁₅. The improvement of the electrocatalytic performance was mainly attributed to the electronic modification effect between Pd and Co as well as the bifunctional mechanism between Pd and Co₂O₃.