核壳结构Ru@PtRu纳米花电催化剂的制备及碱性氢析出反应性能研究

本文通过分步还原Ru、Pt前驱体,制备了以Ru为核、PtRu合金为壳的Ru@Pt_0.24Ru纳米花电催化剂,其平均直径为16.5±4.0 nm. 利用高分辨电子显微镜、电感耦合等离子体原子发射光谱和X射线光电子能谱等表征了这种电催化剂的结构和组成. 在1 mol·L ^-1 KOH水溶液中,核壳结构Ru@Pt_0.24Ru/C纳米花氢析出反应的过电位为22 mV（@10 mA·cm ^-2）,耐久性测试后过电位增加至30 mV（@10 mA·cm ^-2）,明显优于商业Pt/C电催化剂（初始值：60 mV@10 mA·cm ^-2,耐久性测试后：85 mV@10mA·cm ^-2）. 显著提高的电化学活性可能源于核壳结构Ru@Pt_0.24Ru纳米花的电子效应和几何效应,耐久性的改善可能源于核壳结构Ru@Pt_0.24Ru纳米花结构的稳定性.     

SiO2@Fe2O3核-壳结构催化剂的制备及表征

采用优化的Stöber法制备了平均粒径为230 nm的单分散球形SiO₂颗粒,并以此为内核,通过水解沉积法制备了不同壳层厚度的核-壳结构SiO₂@Fe₂O₃催化剂。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂物理吸附和X射线衍射分析(XRD)等手段对催化剂进行表征,探讨了不同制备条件对SiO₂@Fe₂O₃催化剂形貌的影响。结果表明,通过水解沉积法制备的SiO₂@Fe₂O₃催化剂具有明显的核-壳结构,并且保持了原始SiO₂核的球形形貌,Fe₂O₃纳米粒子通过-OH的氢键作用连接在SiO₂表面,形成了2~10 nm厚的Fe₂O₃均匀连续包覆层。     

核壳结构Au@SiO2的可控制备及应用于SERS检测多环芳烃

以金纳米粒子为内核,硅酸钠为硅源,采用自组装法制备了Au@SiO₂核-壳结构,考察了不同反应时间对核壳结构的影响。以4-巯基苯甲酸(4-MBA)为探针分子测试不同厚度Au@SiO₂核壳的表面增强拉曼散射光谱(SERS)性能。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和紫外分光光度计对核壳结构进行表征。结果表明,采用自组装法制备的Au@SiO₂核壳结构粒径均一、稳定性好、壳层厚度可控且对多环芳烃(PAHs)具有吸附能力。将Au@SiO₂核壳结构用于嵌二萘的SERS检测,检出限低至0.1μg/mL。制备的Au@SiO₂核壳结构可以进一步应用于痕量物质的检测。     

Fe_(core)-Pt_(shell)/C核壳型纳米催化剂电催化还原氧的性能

应用两步化学还原法合成不同壳层厚度的Fecore-Ptshell纳米粒子,并用SEM、TEM、EDS和XRD手段对其进行物理表征,应用动电位、交流阻抗和循环伏安法进行氧还原电催化活性及抗甲醇性测试。结果表明,样品Fecore-Ptshell纳米颗粒粒径分布集中,其中Fecore,1-Ptshell,0.5平均值为50nm,核芯直径约34nm,壳层厚度约8nm;与Pt/C相比,Fecore-Ptshell/C对氧还原的催化活性和抗甲醇性明显提高,Fe与Pt原子比为1:0.5的Fecore-Ptshell/C在0.5mol·L-1H2SO4中氧还原的最大峰电流密度可达到184.7mA·mg-1,是相同反应条件下Pt/C电流密度的1.45倍,抗甲醇性显著提高。     

核壳结构AgInS2@ZnS量子点的合成及荧光性能

合成了一种新型核壳结构的AgInS₂@ZnS量子点并研究了其荧光性能. AgInS₂@ZnS的合成包括以变性牛血清白蛋白(dBSA)为稳定剂水相法构建AgInS₂核以及形成ZnS壳两部分. 考察了配方和工艺条件对该量子点荧光性能的影响, 并采用X射线粉末衍射(XRD)等手段对制备的纳米粒子进行了表征. 结果表明, AgInS₂@ZnS是一种核壳结构的纳米物质, 其粒径介于5~7 nm之间, 荧光量子产率达35.3%.     

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.     

核壳结构碳化钨复合微球催化剂对甲醇电催化性能

以偏钨酸铵微球为前驱体,在不同反应时间和CO/CO₂气氛条件下,通过原位还原碳化反应制备了具有核壳结构碳化钨复合微球。采用X射线粉末衍射（XRD）、X射线光电子能谱（XPS）和扫描电镜（SEM）等对催化剂的形貌和结构进行了表征分析。硼氢化钠还原法将平均粒径为4.6 nm的Pt纳米粒子均匀分布在其表面,得到核壳结构碳化钨复合催化剂。采用循环伏安和计时电流法研究了在酸性溶液中催化剂对甲醇的电催化氧化性能。结果表明,与Pt/WC-15 h和JM Pt/C催化剂的电化学性能相比,Pt/WC-6 h催化剂对甲醇呈现出更高的电催化氧化活性和稳定性。碳化钨复合微球表面少量WO₂成分的存在有利于甲醇在其表面的电催化氧化过程的发生。     

铝纳米粒子表面引发聚合制备核壳纳米结构

利用硅烷偶联剂引发法制备核壳结构金属铝纳米粒子(Al NPs)@聚合物, 并研究了聚合反应时间和单体浓度对核壳结构尺寸的影响. 首先合成了硅烷偶联引发剂{2-溴-2-甲基-[3-(三甲氧基硅基)丙基]丙酰胺}, 并通过在甲苯中回流的方法, 将其锚定在金属铝纳米粒子表面. 然后, 在粒子表面引发甲基丙烯酸甲酯的原子转移自由基聚合, 形成聚甲基丙烯酸甲酯(PMMA)壳层. 通过核磁共振波谱仪(NMR)和傅里叶变换红外光谱仪 (FTIR)证明了引发剂和PMMA的成功接枝. 透射电子显微镜(TEM)图像表明, PMMA改性后的金属铝纳米粒子的尺寸和形貌基本不变, 且被厚度约为15 nm聚合物壳层完整均匀地包覆. 此外, 利用动态光散射(DLS)进一步揭示了聚合时间和单体浓度对核壳结构水合直径(D_h)的影响, 发现延长聚合时间或增加单体浓度均可显著提高核壳结构尺寸.     

利用壳层厚度调节核壳Au@Pd纳米粒子的SERS活性

设计合成了一种尺寸可控, 且外壳上无“针孔”的核壳钯包金(Au@Pd)纳米粒子, 通过改变核的尺寸和外壳的厚度来调控其光学性质, 并用TEM、HRTEM、UV-Vis和SERS等手段对其进行了表征. 通过研究Au@Pd纳米粒子的SERS活性随Pd壳层厚度变化的规律, 发现薄壳Au@Pd纳米粒子远远优于Pd金属本身的SERS活性, 其原因主要是内层金核电磁场增强的长程效应.     

采用解离的氢原子作为还原剂制备高氧还原电催化性能的Pd核@Pt壳纳米结构

质子交换膜燃料电池(PEMFC)作为一种清洁、高效的能源转化装置,已经备受学术界与产业界的关注.然而,高活性、高稳定性与低成本的铂基阴极氧还原(ORR)电催化剂的缺乏,严重限制PEMFC的大规模商业化应用.为提高贵金属铂的电催化性能,核壳纳米结构的研究受到广范关注.然而,核壳纳米结构的制备过程通常需要采用有机前驱体、表面活性剂与较高的反应温度,导致大多核壳结构制备方法的大规模应用受到限制.我们在室温下无表面活性剂与高沸点溶剂的参与下,通过钯表面吸附的解离的氢原子来还原K2PtCl4,得到Pd核@Pt壳纳米结构.通过改变加入K2PtCl4的量,可以成功控制壳的厚度;通过透射电子显微镜(TEM)观察得知,我们制备了铂壳厚度分别为0.45,0.75,0.9 nm的核壳结构.Pd核@Pt壳纳米结构的良好的纳米晶体结构与外延生长模式,通过高分辨透射电子显微镜(HRTEM)与能量色散谱仪(EDS)得到证实.同时,所制备Pd核@Pt壳样品的核壳结构通过高角环形暗场-扫描透射-元素分布(HAADF-STEM-EDX)表征方法,得到证实.X射线粉末衍射(XRD)表征证实,样品Pd核@Pt壳并无单独的Pd或Pt衍射峰出现,而是表现出良好的同种晶相结构;相对于单质Pt,样品中Pd核的存在导致Pd核@Pt壳核壳结构表现出一定程度的晶格紧缩.X射线光电子能谱(XPS)表明,钯核的存在导致铂壳的电子结合能增大,并且当铂壳厚度增大到一定程度后,核壳结构引起的电子效应维持不变.通过XPS分峰拟合可知,Pd核@Pt壳结构中零价态的铂含量均在80%以上,并且零价态的铂含量随着铂壳层厚度的增大而增大.采用电感耦合等离子体(ICP)与XPS,发现铂的表面富集现象,并且铂表面富集现象随着铂壳层厚度的增大而增大.在半电池中,经过循环伏安扫描活化,Pd核@Pt壳表现出明显的铂的氢吸附与脱附特征峰,再次证明了铂壳层的成功包覆.Pd核@Pt壳纳米颗粒表现出优于Pt/C(JM)的面积比活性、质量比活性及电化学稳定性.核壳结构的良好的ORR电催化性能,来源于催化剂表面含氧物种吸附强度的减弱;上述现象归因于钯核与铂壳之间的电子效应与晶格应力效应.此处简易、清洁的核壳结构制备方法也可以用来在温和条件下制备Ni核@Pt壳等核壳结构.     

Pt@Au/Al2O3核壳纳米粒子的制备和表征及其在催化氧化甲苯中的应用

Customizing core-shell nanostructures is considered to be an efficient approach to improve the catalytic activity of metal nanoparticles. Various physiochemical and green methods have been developed for the synthesis of core-shell structures. In this study, a novel liquid-phase hydrogen reduction method was employed to form core-shell Pt@Au nanoparticles with intimate contact between the Pt and Au particles, without the use of any protective or structure-directing agents. The Pt@Au core-shell nanoparticles were prepared by depositing Au metal onto the Pt core; AuCl⁴⁻ was reduced to Au(0) by H₂ in the presence of Pt nanoparticles. The obtained Pt@Au core-shell structured nanoparticles were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM, fast Fourier transform, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and H₂-temperature programmed reduction (H₂-TPR) analyses. The EDX mapping results for the nanoparticles, as obtained from their scanning transmission electron microscopy images in the high-angle annular dark-field mode, revealed a Pt core with Au particles grown on its surface. Fourier transform measurements were carried out on the high-resolution structure to characterize the Pt@Au nanoparticles. The lattice plane at the center of the nanoparticles corresponded to Pt, while the edge of the particles corresponded to Au. With an increase in the Au content, the intensity of the peak corresponding to Pt in the FTIR spectrum decreased slowly, indicating that the Pt nanoparticles were surrounded by Au nanoparticles, and thus confirming the core-shell structure of the nanoparticles. The XRD results showed that the peak corresponding to Pt shifted gradually toward the Au peak with an increase in the Au content, indicating that the Au particles grew on the Pt seeds; this trend was consistent with the FTIR results. Hence, it can be stated that the Pt@Au core-shell structure was successfully prepared using the liquid-phase hydrogen reduction method. The catalytic activity of the nanoparticles for the oxidation of toluene was evaluated using a fixed-bed reactor under atmospheric pressure. The XPS and H₂-TPR results showed that the Pt₁@Au₁/Al₂O₃ catalyst had the best toluene oxidation activity owing to its lowest reduction temperature, lowest Au 4d & 4f and Pt 4d & 4f binding energies, and highest Au⁰/Au^δ+ and Pt⁰/Pt²⁺ proportions. The Pt₁@Au₂Al₂O₃ catalyst showed high stability under dry and humid conditions. The good catalytic performance and high selectivity of Pt@Au/Al₂O₃ for toluene oxidation could be attributed to the high concentration of adsorbed oxygen species, good low-temperature reducibility, and strong interaction.     

同晶外延生长法合成MFI型核壳复合分子筛

采用二次热液结晶法,以四丙基氢氧化铵水溶液预处理过的低硅ZSM-5分子筛为晶核,通过调控p H值、水量和晶化时间等二次结晶条件,在晶核上外延生长了高硅ZSM-5壳,制备了MFI/MFI核壳型复合分子筛。通过X射线衍射、扫描电镜、能量色散谱仪、透射电子显微镜、N2吸附-脱附和NH3-程序升温脱附等手段表征了所合成的核壳分子筛的晶体结构、表面形态及核/壳界面,并对它们的结构参数以及酸性进行了初步评估。结果表明,核壳复合分子筛的壳层由多层200 nm的MFI沸石晶粒组成;高硅ZSM-5分子筛壳层的生成,引入了介孔结构,显著增大了外比表面积;同时,核壳结构的形成降低了复合分子筛酸性和外表面的酸密度,但增加了弱酸量。当二次晶化母液p H值为8.5,H2O/SO2物质的量比为30,晶化时间为24 h时,高硅分子筛壳层更易可控生长。     

Silica-supported PtSn alloy doped with Ga, In or, Tl: Characterization and catalytic behaviour in n-hexane dehydrogenation

Silica-supported trimetallic catalysts containing Pt, Sn and a group 13 metal (PtSnM, M=Ga, In, Tl) were prepared by consecutive impregnation steps from cis-[PtCl₂(PPh₃)₂] and chloride precursors. X-ray diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (ED) and energy dispersive X-ray analysis (EDX) showed large platelet-like particles of PtSn_1−xM_x phases. PtSnGa catalyst with a Pt/(Sn+Ga) molar ratio of 1.72 showed a bimodal particle distribution and a Pt phase was identified. Differences in surface structures were also revealed by the performance of catalysts in the dehydrogenation of n-hexane. For PtSnIn and PtSnTl (Pt/(Sn+M) molar ratio of about 1) the dehydrogenation was favoured. In contrast, PtSnGa catalyst yielded hydrogenolysis products. Photoelectron spectra showed the Pt 4f_7/2 level at a binding energy of 70.0–71.8 eV in all cases. Moreover, the FT-IR spectra of chemisorbed CO on the PtSnGa showed a slight shift in the ν(CO) toward higher values with respect to the monometallic catalyst, pointing to an electronic effect in accordance with photoelectron spectroscopy.     

An improved Brust’s procedure for preparing alkylamine stabilized Pt, Ru nanoparticles

An improved method to prepare alkylamine-stabilized Pt and Ru nanoparticles based on the original Brust’s procedure [J. Chem. Soc., Chem. Commun. (1994) 801] has been developed. The new method involves, firstly, mixing an aqueous solution of metal salts such as PtCl₆²⁻, PtCl₄²⁻ or Ru³⁺ with an ethanol solution of dodecylamine; extracting the metal ions into a toluene layer; and finally reducing the metal ions to their zero valent states using NaBH₄. Alkylamine-stabilized Pt nanoparticles prepared this way had a polyhedral or wormlike appearance, depending closely on the chemical nature of the metal precursor salts being used. On the contrary, dodecylamine-stabilized ruthenium nanoparticles were predominantly spherical. The particle formation and growth processes in the hydrocarbon layer could be influenced by the different ways dodecylamine was bound to H₂PtCl₆, K₂PtCl₄ or RuCl₃ at the precursor stage.     

Fabrication of PtRu/Ru core–shell nanowires by exchanging Ru phases

In this study, we successfully fabricated PtRu/Ru core–shell nanowires (NWs) prepared from as-spun Ru/Pt core–shell NWs via a co-electrospinning method. Their formation mechanism together with the structural characteristics, morphology, and composition of the resulting PtRu/Ru core–shell NWs was elucidated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). PtRu/Ru core–shell NWs fabricated from as-spun Ru/Pt core–shell NWs were formed as a result of interdiffusion between Ru atoms and Pt atoms during calcination after co-electrospinning.     

三组Pt- Ru/C催化剂前驱体对其性能的影响

分别以三组不同的Pt和Ru化合物为前驱体, 采用热还原法制备了Pt-Ru/C催化剂, 比较不同前驱体对催化剂性能的影响；通过XRD和TEM技术对催化剂的晶体结构及微观形貌进行了分析. 结果表明以H₂PtCl₆+RuCl₃和自制(NH₄)₂PtCl₆+Ru(OH)₃为前驱体的催化剂Pt和Ru没有完全形成合金状态, 在Pt(111)和Pt(200)之间有Ru(101)存在；以Pt(NH₃)₂(NO₂)₂和自制含钌化合物为前驱体制备的催化剂未检测出Ru金属或其氧化物的衍射峰, Pt-Ru颗粒在载体上分散均匀, 粒径最小, 为3.7 nm. 利用玻碳电极测试了循环伏安、记时电流和阶跃电位曲线, 考核了上述催化剂对甲醇阳极催化氧化活性的影响；结果表明：以Pt(NH₃)₂(NO₂)₂和自制含钌化合物为前驱体制备的催化剂对甲醇的电催化氧化活性最高, 循环伏安曲线峰电流密度达11.5 mA•cm^-2.     

Synthesis and structural characterization of Se-modified carbon-supported Ru nanoparticles for the oxygen reduction reaction

This work is part of a continued research aimed at the understanding of the promoting role of Se in the enhancement of the electrocatalytic activity of Ru in the oxygen reduction reaction. The objective of this paper is to systematically investigate the transformation of Ru nanoparticles upon their modification with the increasing amounts of Se. The Se-modified Ru/C samples with Se:Ru ratio from 0 to 1 were prepared by reacting carbon-supported Ru nanoparticles with SeO2 followed by reductive annealing and characterized using high-resolution transmission electron microscopy, energy-dispersive X-ray, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure. The results suggest that Se strongly interacts with Ru, resulting in the chemical bond between Ru and Se and formation of Ru selenide clusters whose core at low Se content can be described as Ru2Se2O0.5. At Se:Ru = 1, high-resolution electron microscopy shows evidence of formation of core-shell particles, comprising a hexagonally packed Ru core and a Ru selenide shell with lamellar morphology. Modification of Ru nanoparticles with Se enhances their electrocatalytic activity in the oxygen reduction reaction, which is explained by the role of Se in inhibiting surface oxidation.     

纳米Fe@SiO2一步合成及其对Cr(VI)的去除

利用液相还原与改进的St(o)br法相结合,在不使用表面改性剂和氨水的条件下,通过向原硅酸乙酯(TEOS)和氯化铁混合溶液直接添加硼氢化钾,一步合成了二氧化硅包覆的纳米铁复合材料(Fe@SiO2).通过X射线粉末衍射(XRD)仪、能量色散X射线仪(EDAX)、透射电子显微镜(TEM)、紫外-可见(UV-Vis)吸收分光光度计、傅里叶红外(FTIR)光谱仪、X射线光电子能谱仪(XPS)等对所得样品的形貌、结构和组成进行表征.将制备的Fe@SiO2用于水体中Cr(VI)还原去除并考察了TEOS添加量对其去除能力的影响.结果表明Fe@SiO2具有清晰的核壳结构,多孔的SiO2层包裹1-2个球形纳米铁粒子.纳米铁粒径主要分布在20-30 nm之间,随着TEOS投加量的增加,SiO2层变厚,纳米铁核具有更好的分散性.与未包覆型纳米铁相比,Fe@SiO2对Cr(VI)的去除能力显著提高.TEOS投加量为0.1 mL所制备的Fe@SiO2对Cr(VI)去除能力(以Fe的质量计算)达到最大,为466.67 mg·g-1,而未包覆型纳米铁仅为76.35 mg·g-1.