Synthesis and Evaluation of Pt-Fe Alloy Nano-Particles for Cathode Catalyst of Polymer Electrolyte Fuel Cells

为开发聚合物-电解液燃料电池(PEFCs)新型高效阴极催化剂，采用化学湿法合成了纳米粒子PT_&lt；50&gt；-Fe_&lt；50&gt；用透射电子显微镜、X射线衍射仪、穆斯堡尔谱和X射线光电子能谱分别对合成的铂-铁颗粒的形貌、晶体结构和铁原子的电子态进行了表征。从X射线衍射谱确定它们是化学无序的面心立方结构，由透射电子显微镜和X射线衍射谱的(111)峰宽度估算出它们的平均直径为3.1 nm。从TMS谱可以看出，它们主要是由与有机配体相连的铁氧化物组成，结合XPS结果。但是，它可能含有超顺磁性铂-铁纳米颗粒的成分。…的电催化活性和氢的吸附/脱附行为用循环伏安法测定了合成的铂-铁纳米颗粒中铁原子的氧化程度，并测定了合成的铂-铁纳米颗粒、金属铁和铁氧化物中铁原子的氧化情况。X射线光电子能谱(XPS)证实，Ar溅射可以部分去除合成的铂-铁纳米颗粒中与有机配体相连的铁氧化物，并将合成的铂-铁纳米颗粒暴露在氢气软等离子体中得到金属铂-铁纳米颗粒。此外，在630℃下进行5min的退火处理。在Ar+4%H_2气氛中，用X射线衍射仪和TMS分析了样品的FCT结构。目前，我们已经制备了金属铂-铁纳米粒子及其退火态的循环伏安曲线，并用等离子体-气体冷凝技术初步合成了用于PEFCs阴极催化剂的铂-铁纳米团簇。分别用穆斯堡尔谱(MS)和卢瑟福背散射(RBS)分析了铁的复合态和电子态。结果表明，样品中含有α-Fe组分，需要用X射线光电子能谱和低温质谱仪来研究样品中Fe原子的化学状态。我们研制了一种低能X射线探测器，该探测器由Avarach型光电二极管和CsI(Tl)闪烁体组成，可以在不制冷的情况下探测14.4keV的γ射线，目前正在尝试测量5.9keV的K射线，用于转换X射线穆斯堡尔谱。较少

Pt_<50>-Fe_<50> nanoparticles were synthesized by the chemically wet process for developing a new high efficiency cathode catalyst in Polymer-Electrolyte Fuel Cells(PEFCs). The particle morphology and crystal structure of as synthesized Pt-Fe particles, and electronic state of Fe atoms in them were evaluated using transmission electron microscopy(TEM), X-ray diffraction(XRD), transmission Mossbauer spectroscopy(TMS) and X-ray Photoelectron Spectroscopy(XPS), respectively. They are confirmed to be of chemically disordered fcc structure from XRD pattern and the average diameter of them was estimated to be 3.1 nm from both TEM and the width of(111) peak in XRD pattern. From TMS spectrum, it was concluded that they consist of mainly the component of Fe oxides connected with the organic ligands in consideration of XPS results. But, probably it contains the component for superparamagnetic Pt-Fe nanoparticles. Also the electrocatalytic activity and a hydrogen adsorption/desorption behavior fo … More r as synthesized Pt-Fe nanoparticles was observed by cyclic voltammetry and the oxidation of Fe atoms in as synthesized Pt-Fe nanoparticles, Fe metal and Fe oxides were measured. It is confirmed by XPS that Fe oxides connected with the organic ligands in as synthesized Pt-Fe nanoparticles can be removed partially by Ar sputtering and the metallic Pt-Fe nanoparticles were obtained by exposing the as synthesized to H_2 soft plasma. Furthermore, as annealed sample at 630℃ for 5min. in Ar+4%H_2 atmoshere was observed to be ordered fct structure by XRD and TMS. At the present, the measurements of CV curves for the metallic Pt-Fe nanoparticles and as annealed samples are prepared.Pt_<50>-Fe_<50> alloy nano-clusters for cathode catalyst of PEFCs were also synthesized tentatively by using a Plasma-Gas-Condensation Technique. The composite and electronic states of Iron for them have been evaluated by Mo ssbauer spectroscopy (MS) and, Rutherford Back-Scattering (RBS) analysis, respectively. It was found that the sample includes α-Fe component and chemical state for Fe atoms in Pt-Fe alloy nano-clusters has to be investigated by XPS measurement and low temperature MS.Low energy X-ray detector which consist of avarache photodiode and CsI(Tl) scintillater has been developed to detect 14.4 keV γ-ray without cooling and now is tried to measure 5.9 keV K X-ray of ^<55>Fe for Conversion X-ray Mossbauer spectroscopy with cooling by Peltier device. Less