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

采用化学湿法合成了Pt_<50>-Fe_<50>纳米颗粒，用于聚合物-电解质燃料电池（pefc）中高效阴极催化剂的开发。采用透射电镜（TEM）、x射线衍射（XRD）、透射穆斯堡尔能谱（TMS）和x射线光电子能谱（XPS）分别对合成的Pt-Fe粒子的颗粒形貌和晶体结构以及其中铁原子的电子态进行了表征。XRD谱图证实其为化学无序fcc结构，TEM谱图和（111）峰宽度估计其平均直径为3.1 nm。从TMS谱分析中，结合XPS结果，得出它们主要由与有机配体连接的铁氧化物组成。但是，它可能含有超顺磁性Pt-Fe纳米粒子的成分。用循环伏安法观察了合成的Pt-Fe纳米粒子的电催化活性和氢吸附/解吸行为，并测定了合成的Pt-Fe纳米粒子中铁原子的氧化、金属铁和铁氧化物的氧化。XPS证实，Ar溅射可以部分去除所合成的Pt-Fe纳米颗粒中与有机配体连接的Fe氧化物，将所合成的Pt-Fe纳米颗粒暴露在H_2软等离子体中得到金属Pt-Fe纳米颗粒。在Ar+4%H_2气氛中，630℃退火5min后，XRD和TMS观察到样品呈有序结构。目前，制备了金属Pt-Fe纳米颗粒和退火样品的CV曲线测量方法。采用等离子体-气体冷凝技术，初步合成了用于pefc阴极催化剂的Pt_<50>-Fe_<50>合金纳米团簇。分别用莫斯堡尔谱（MS）和卢瑟福背散射（RBS）分析了它们的铁的复合态和电子态。发现样品中含有α-Fe成分，Pt-Fe合金纳米团簇中Fe原子的化学状态需要用XPS测量和低温ms来研究。研制了由avarache光电二极管和CsI（Tl）闪烁体组成的低能x射线探测器，可以探测14.4 keV γ射线而不冷却，现在正尝试用珀尔帖装置测量5.9 keV K x射线^<55>Fe的转换x射线穆斯堡尔光谱。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