金核/铂壳纳米粒子的光化学合成及电催化活性

在含不同摩尔比的Au(Ⅲ)和Pt(Ⅳ)离子的PEG(聚乙二醇)-丙酮溶液中,采用光化学共还原法合成了一组Au@Pt复合纳米粒子,并以炭黑分别对其负载制成Au@Pt/C催化剂。借助于UV-Vis、TEM和HR-TEM的表征,证实复合纳米粒子为球形的核/壳结构;分别以XPS、EDS和电化学方法分析了复合粒子的化学状态、结构特点和Au@Pt/C催化剂的催化性质。结果表明,不同Au:Pt摩尔比的Au@Pt/C催化剂对甲醇氧化反应具有良好的催化活性和稳定性,其中Au:Pt=1:1时形成的Au@Pt/C催化剂电催化活性最高,约为商品Pt/C催化剂的4倍。简要讨论了核/壳结构产生高催化活性的主要原因。     

PtPb/ C 催化剂的制备及其对甲酸电氧化的催化性能

目的通过Pb元素的添加来提高Pt/C催化剂电催化氧化甲酸的性能。方法通过乙二醇协助硼氢化钠还原法,以氯铂酸为Pt源和硝酸铅为Pb源制备不同原子比的PtxPb/C催化剂。采用X射线衍射光谱法(XRD)和透射电子显微镜技术(TEM)表征样品的晶体结构和颗粒形貌;采用循环伏安法表征样品催化氧化甲酸的性能。结果利用乙二醇协助硼氢化钠还原法成功制得了Pt和Pb原子比不同的PtxPb/C催化剂,XRD和TEM测试结果表明这些样品均为Pt的面心立方结构,且颗粒大小均一、分散均匀,其平均粒径为4 nm左右。循环伏安测试结果表明PtxPb/C催化剂催化氧化甲酸的性能优于商业Pt/C催化剂的催化性能,且受Pt和Pb原子比的影响,当原子比为5∶1时,其对氧化甲酸的催化性能最好,峰电位对应的Pt的比质量活性达到2000 m A/(mg Pt),远远高于商业Pt/C,同时计时电流曲线表明其具备良好的稳定性。结论 Pb原子的加入影响了Pt原子的电子结构,与Pb对Pt的协同作用共同促进了CO等中间产物在Pt表面的快速氧化,降低了催化氧化甲酸的初始电位,促使甲酸在低电位直接氧化为CO2和H2O,提高了其催化氧化甲酸的峰电流,有效减轻了Pt中毒,提高了其催化活性。     

Comparative studies of adsorbed CO and methanol electrooxidation on carbon supported Pt and PtRu catalysts in acid solution

1. Introduction Direct methanol fuel cells (DMFCs) have con-siderable advantages compared to gas feed (H2/air) polymer electrolyte membrane (PEM) fuel cells [1-2]. The hydrogen PEM fuel cells use gaseous hy-drogen as fuel. But there is no source and infra-structure established yet for hydrogen distribution and storage, neither as a liquid nor as a gas. How-ever, the DMFC, similar to a proton exchange membrane fuel cell (PEMFC), uses methanol fuel directly for electric power generation …     

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%。     

Fabrication, annealing, and electrocatalytic properties of platinum nanoparticles supported on self-organized TiO2 nanotubes

The platinum nanoparticles supported on self-organized TiO2 nanotubes （Pt-TiO2/Ti） were prepared using electrochemical anodic oxidation followed by cathodic reduction. The structure and chemical nature of the Pt-TiO2/Ti electrocatalyst were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Both XRD and SEM results indicate the presence of platinum on nanotubular TiO2. The stability of the Pt deposits was also investigated in 0.5 mol/L H2SO4 solution by cyclic voltammetry. The electrocatalytic activity of the Pt-TiO2/Ti catalyst exhibits enhancement effect during electro-oxidation of methanol when annealed to anatase. Successive cyclic voltam- mograms of methanol oxidation on the Pt-TiO2/Ti electrocatalyst shows unique electrocatalytic characteristics when compared to methanol oxidation on the bulk Pt catalyst. This is because of further quick oxidation of adsorbed CO by Pt （111） facets of Pt particles on self-organized TiO2 nanotubes when the formation of an electroactive film onto the working catalyst surface occurs.     

Pt掺杂的纳米Ni电催化氧化甲醇性能的研究

采用溶胶凝胶法制备了碳载纳米双金属Ni-Pt(5%,质量分数)/C电催化剂,用TEM、XRD和XPS表征金属粒子的形貌、晶相结构、表面元素及其价态,循环伏安法测试催化剂在碱性溶液中电催化氧化甲醇的活性。结果表明,Ni-Pt金属粒子在碳载体上分布均匀,粒径为3～6nm,少量Pt的掺杂对纳米Ni活性有明显提高,其中,合金型Ni-Pt(5%)/C在1.0mol/LNaOH+1.0mol/LCH3OH溶液中峰电流密度可达85.6mA/mg,是Ni/C峰电流密度的8.7倍,达到Pt/C峰电流密度的15.3%。单位质量铂的电流显著提高。     

Synthesis and study of λ-MnO_2 supported Pt nanocatalyst for methanol electro-oxidation

A λ-MnO2 supported Pt nanocatalyst(5 wt.% Pt/λ-MnO2) was synthesized using a facile approach.X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), scanning electronic microscope(SEM), transmission electron microscopy(TEM), and energy disperse spectroscopy(EDS) were used for catalyst structure and morphology characterization, which showed that the metallic Pt particles were attached on a λ-MnO2 surface through the interaction between Pt and λ-MnO2.Cyclic voltammetry(CV) was used to test the catalytic activity of Pt/λ-MnO2 toward methanol oxidation, which showed that Pt/λ-MnO2 catalyst has much higher catalytic activity than baseline Pt/C catalyst.     

聚苯胺增强 Pt / C 催化剂活性和稳定性研究

目的制备一种具有高稳定性和高催化活性的Pt/C@PANI"核/壳"结构催化剂。方法利用原位化学氧化聚合法制备聚苯胺修饰Pt/C@PANI"核/壳"结构催化剂,采用循环伏安加速寿命实验,结合电化学活性表面积、氧还原活性、X-射线光电子能谱和透射电镜,考察所制备催化剂的活性和稳定性,通过密度泛函理论探究PANI增强Pt/C催化剂活性和稳定性的量子化学本质原因。结果电化学测试表明, Pt/C@PANI催化剂的催化活性与聚苯胺包覆层含量和厚度密切相关,Pt/C@PANI(30%)催化剂具有最好的催化活性,其质量比活性和比表面比活性分别为商业化Pt/C催化剂的1.6和1.8倍。加速寿命实验表明,Pt/C@PANI(30%)催化剂具有很好的稳定性,经过1500圈CV扫描后,其电化学活性表面积仅下降了30%,而商业化Pt/C催化剂降低了83%。理论计算表明,PANI将电子转移给载体C,导致自身空穴增加,PANI部分氧化,导电性增强;PANI的存在使Pt/C@PANI体系的HOMO能级升高,减小了与氧气分子LUMO能级的差异,有利于电子从催化剂HOMO转移到氧分子的LUMO轨道,使得氧容易得到电子;PANI吸附后,Pt原子d带中心显著降低,利于中间物种的脱附,催化活性更高。结论 PANI包覆层抑制了Pt纳米粒子在载体表面的迁移、团聚长大和溶解/再沉积,有效地解决了Pt/C催化剂的Ostwald肿大,催化剂的活性和稳定性得到显著提升。     

碳载金铂双金属催化剂催化活性研究

采用KBH4做还原剂、PVP做保护剂,化学法一步合成Au-Pt合金纳米粒子,应用UV-Vis、TEM、XRD等手段对其进行了表征.将所合成的合金纳米粒子负载在碳黑上,获得Au-Pt双金属碳载催化剂,应用循环伏安法(CV)检测了催化剂对甲醇的电催化氧化活性.研究表明,Au-Pt/C催化剂的催化活性明显高于Pt/C的,说明...     

碳载铂纳米微粒修饰的玻碳电极对甲醇的电催化氧化

利用X射线粉末衍射、透射电镜和扫描电镜对商用Pt/C催化剂反应前后的变化进行了物化表征，同时应用电化学方法研究了甲醇在碳载铂纳米微粒修饰的玻碳电极上的电催化氧化性能。结果表明，修饰电极对甲醇氧化呈现较高的电催化活性。铂氧化物的电化学还原在Pt/c催化剂中受到了抑制，该现象可能是由于Pt与载体碳间的强烈作用所引起的。通过扫描电镜和循环伏安研究表明，该催化剂对甲醇的氧化可能存在着表面结构敏感效应。     

热处理对Pt纳米线电催化性能的影响

采用阳极氧化铝(AAO)模板法电化学沉积制备了Pt纳米线催化剂,并进行了热处理。通过X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学测试对热处理前后Pt纳米线催化剂的晶体结构、形貌和电催化性能进行了表征,并与商业碳载铂(Pt/C)做对比。SEM照片表明制备了表面粗糙的Pt纳米线。循环伏安法(CV)和计时电流曲线表明,Pt纳米线较Pt/C催化活性高,退火后Pt纳米线更利于甲醇氧化,且稳定性更好。旋转圆盘电极(RDE)测试研究发现,未经热处理的Pt纳米线催化剂氧还原反应(ORR)极化曲线的半波电势相对Pt/C有正移,有更大的极限扩散电流,利于氧还原反应的发生。     

喷雾干燥法制备碳载铂钴镍合金催化剂及其甲醇催化氧化性能研究

本文以氯铂酸、氯化镍和硝酸钴为原料,XC-72炭黑为载体,通过雾化干燥法结合煅烧还原制备碳载铂基（PtCo Ni）分散性好的多元合金纳米粒子催化剂。重点研究表面经过改性的炭黑对合金纳米粒子形成和分散的影响规律,研究碳载PtCoNi（原子比为1:1:1）合金纳米粒子的甲醇催化氧化活性、抗CO中毒能力和耐久性,以及不同原子比对催化氧化甲醇活性和抗CO中毒能力的影响规律。研究结果表明,采用表面改性后的炭黑作为载体,制备的碳载铂基（PtCoNi）催化剂为合金纳米粒子,且纳米粒子在炭黑表面分散均匀,粒径分布在1-4nm,平均粒径为2.3nm;与商用的Pt/C催化剂相比,PtCoNi/C（原子比为1:1:1）催化剂具有更高的甲醇催化氧化活性、耐久性和抗CO中毒性;不同原子比铂基多元催化剂在催化氧化甲醇活性上的顺序为：PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C,抗CO中毒性顺序为：PtCoNi/C>Pt3CoNi/C>Pt5CoNi/C。     

Ti/nano-TiO2-Pt复合电极催化甲醇氧化的研究

采用溶胶-凝胶法(sol-gel)制备纳米TiO2(Ti/nano-TiO2)膜电极,再用电沉积法在纳米TiO2膜上修饰Pt微粒,制成Ti/nano-TiO2-Pt复合电极.用循环伏安法研究了纯Pt丝电极和Ti/nano-TiO2-Pt电极对甲醇氧化的电催化活性以及稳定性.结果表明:对甲醇氧化,复合电极比Pt丝电极具有更高的催化活性,且对甲醇氧化中间产物CO的吸附量少,因而不易中毒;复合电极载铂量达到一定值时,电极具有最强的催化活性.     

一步微波有机溶胶法制备燃料电池Pt/C电催化剂

采用一步微波有机溶胶法制备了系列20%Pt/C燃料电池催化剂。考察了不同硝酸浓度氧化处理碳粉的表面、微波反应时间以及还原剂乙二醇(EG)的用量等因素对催化剂电催化活性的影响。实验发现:无论是阳极还是阴极反应,处理碳粉时硝酸浓度为40%、微波反应时间70 s时制备的催化剂活性最好;然而,阳极甲醇氧化时制备催化剂EG用量较少、活性高,阴极氧还原时EG用量较多反而有利。采用X射线衍射(XRD)、透射电镜(TEM)、循环伏安法(CV)等方法对催化剂进行测试。结果表明,不同考察因素对于活性组分的结构、晶型及粒径没有太大影响,但对电化学活性比表面积和电催化活性有显著影响。     

钯锰纳米多孔材料对乙醇的电催化氧化

采用熔体快淬结合去合金化法制备了钯锰纳米多孔材料(NP-PdMn)。用X射线衍射(XRD)、X射线光电子能谱分析(XPS)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对材料进行了表征,并研究了其在碱性条件下对乙醇氧化的电催化活性。表征显示,NP-Pd Mn为具有三维双连续纳米多孔结构的棒状材料;锰取代了晶格中部分钯的位置使得晶面间距变小;部分钯和锰在材料表面以氧化态存在。催化性能分析表明,与商业Pd/C相比,NP-PdMn/C催化剂具有优于商业Pd/C的催化活性和稳定性。     

Preparation and characterization of platinum doped porous titania nanoparticles for photocatalytic oxidation of carbon monoxide

TiO₂ samples doped with platinum oxide were obtained by using a sol-gel low temperature approach. The photocatalytic oxidation of CO in the presence of O₂ was monitored to study the influence of the Pt doping on the photocatalytic degradation performance of TiO₂. The obtained results were compared with those obtained with TiO₂ Degussa (P-25). Photocatalytic studies of the prepared mesoporous Pt/TiO₂ nanoparticles for the photooxidation of CO revealed notable photocatalytic activity, which was 3 times higher than that of Pt photodeposited onto commercial TiO₂ Degussa P-25. Also quantum yield for CO₂ formation for mesoporous Pt/TiO₂ calcined at 500 °C is higher than that of Pt photodeposited onto commercial TiO₂ Degussa P-25 by about three times. The structure and textural properties Pt/TiO₂ were studied by X-ray powder diffraction (XRD), N₂ adsorption (BET), Transmission electron microscopy (TEM) and UV.     

DMFC阳极催化剂的失活特性

采用电化学老化试验考察直接甲醇燃料电池(DMFC)阳极PtRu/C催化剂的失活过程.结果表明,老化试验后PtRu/C催化剂的甲醇氧化活性明显降低.透射电镜和X射线衍射分析结果表明,在老化试验中催化剂粒子经历了Otswald熟化过程和电场作用下的微晶定向迁移过程.电化学阻抗谱分析表明,老化试验后催化层的欧姆电阻和极化阻抗都显著增加,这与活性组分的流失有关.X射线能谱分析显示,老化试验后催化剂的Pt:Ru质量比显著升高.由电位波动引起的活性组分流失是导致DMFC阳极催化剂失活的重要原因.     

New Pt–Ru solid compounds as precursors of anodic catalysts for direct methanol fuel cell

This research is aimed to increase the activity of platinum–ruthenium alloy catalysts, thus to lower the catalyst loading in anodes for methanol electrooxidation. The DMFC catalyst consisting of Pt–Ru/C were prepared from (NH₄)₂PtCl₆ and Ru(OH)₃ as solid precursors at different temperatures and times of duration during their reduction. Their performances were examined by cyclic voltammograms and chronoamperometric curves. The particle size and its distribution in the catalysts were determined by means of TEM and XRD. It is found that the XRD patterns of the catalyst prepared from (NH₄)₂PtCl₆ and Ru(OH)₃ as precursors show Pt reflexions with f.c.c. crystal structure. There are diffraction peaks indicating the presence of either pure Ru or a Ru-rich h.c.p. phase, which has not been alloyed with Pt in Pt–Ru/C. The activity of the Pt–Ru/C catalysts prepared from (NH₄)₂PtCl₆ and Ru(OH)₃ as precursors is higher than those obtained from H₂PtCl₆ and RuCl₃ by chemical or thermal reduction. The activity of Pt–Ru/C catalysts prepared at 360 °C is higher than those prepared at 320 and 400 °C. After 1 h of reduction at 360 °C its particle size is small, about 7.5 nm, and its catalytic activity is higher than those obtained after 2 and 3 h of reduction.     

Studies on the electrocatalytic properties of PtRu/C-TiO2 toward the oxidation of methanol

PtRu/C-TiO₂ catalysts were prepared by hydrolysis of Ti(OBu)₄ on commercial PtRu/C. The catalyst was characterized by XRD, TEM, and XPS. The electrochemical performance of catalysts was testified by cyclic voltammetry (CV) and chronoamperometry (CA) in 0.5 M C₂H₅OH + 0.5 M H₂SO₄ solution. The results showed that the added TiO₂ can improve the electrocatalytic properties of the catalyst toward methanol oxidation. The mechanism for the effects of TiO₂ on catalytic activity of PtRu/C to methanol oxidation is also discussed.     

喷雾干燥法制备铂镍合金三维纳米骨架材料及增强甲醇氧化性能研究

本文以氯铂酸氨和氯化镍为原料,氯化铵作为造孔剂,通过雾化干燥法结合煅烧还原制备铂镍合金三维纳米骨架材料,该新型材料可增强催化甲醇氧化性能。重点研究了前驱体中加入氯化铵和不加入对铂镍合金三维纳米骨架形成的影响规律,研究不同结构的铂镍合金三维纳米骨架材料对催化氧化甲醇活性和稳定性的影响规律。研究结果表明,通过加入适量的氯化铵作为造孔剂,制备的铂镍合金为单项固溶体结构(面心立方结构),由弯曲纳米线交织组成三维纳米骨架材料,纳米线直径小于10 nm,纳米孔10 nm左右;与商用Pt黑和不加入氯化铵制备的铂镍合金纳米材料相比,PtNi合金三维纳米骨架材料具有更高的甲醇催化氧化活性(611.4 mA.mg_^-1Pt),分别是商用Pt黑的3.58倍(170.8 mA.mg_^-1Pt)和PtNi合金纳米材料(不加氯化铵)的1.36倍(448.8 mA.mg_^-1Pt);在催化甲醇氧化性能稳定性上,PtNi合金三维纳米骨架材料表现出最好的稳定性,稳定性顺序为：PtNi合金三维纳米骨架材料 > PtNi合金纳米材料(不加氯化铵)> 商用Pt黑。此外,本文对该方法进行了扩展,成功的制备了铂镍钴铜钌铱钯(PtNiCoCuRuIrPd)高熵合金三维纳米骨架材料。