新型钴-聚吡咯-碳载Pt燃料电池催化剂的制备与表征

采用脉冲微波辅助化学还原法制备了钴-聚吡咯-碳(Co-PPy-C)载Pt催化剂(Pt/Co-PPy-C),其中Pt的总质量占20%.利用透射电镜(TEM)、光电子射线能谱分析(XPS)和X射线衍射(XRD)研究了催化剂的结构,用循环伏安(CV)、线性扫描伏安(LSV)等方法考察了其电化学活性及氧还原反应(ORR)动力学特性及耐久性.Pt/Co-PPy-C电催化剂的金属颗粒直径约1.8 nm,略小于商用催化剂Pt/C(JM)颗粒尺寸(约2.5 nm);催化剂在载体上分散均匀,粒径分布范围较窄.Pt/Co-PPy-C的电化学活性比表面积(ECSA)(75.1 m2·g-1)高于商用催化剂的ECSA(51.3 m2·g-1).XPS测试表明,自制催化剂表面的Pt主要以零价形式存在.而XRD结果显示,自制催化剂中Pt(111)峰最强,Pt主要为面心立方晶格.Pt/Co-PPy-C具有与Pt/C(JM)相同的半波电位;在0.9 V下,Pt/Co-PPy-C的比活性(1.21 mA·cm-2)高于商用催化剂的比活性(1.04 mA·cm-2),表现出更好的ORR催化活性.动力学性能测试表明催化剂的ORR反应以四电子路线进行.CV测试1000圈后,Pt/Co-PPy-C和Pt/C(JM)的ECSA分别衰减了13.0%和24.0%,可见自制催化剂的耐久性高于商用Pt/C(JM),在质子交换膜燃料电池(PEMFC)领域有一定的应用前景.

Preparation and Characterization of Pt Catalysts Supported on Cobalt-Polypyrrole-Carbon for Fuel Cells

Pt/cobalt-polypyrrole-carbon (Co-PPy-C)-supported catalysts were successfully prepared by pulse-microwave assisted chemical reduction. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques were used to characterize the catalyst microstructure and morphology. The electrocatalytic performance, kinetic characteristics of the oxygen reduction reaction (ORR), and durability of the catalysts were measured by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques. It was found that the particle size of Pt/Co-PPy-C was about 1.8 nm, which was smaller than that of commercial Pt/C (JM) catalysts (2.5 nm). The metal particles were well-dispersed on the carbon support. The electrochemical specific area (ECSA) of Pt/Co-PPy-C (75.1 m²· g^-1) was much higher than that of Pt/C (JM) (51.3 m²·g^-1). The results of XPS showed that most of the Pt in the catalysts was in the Pt(0) state, and XRD results showed that the form of Pt was mainly the facecentered cubic lattice. The Pt/Co-PPy-C catalyst had the same half-wave potential as Pt/C (JM) and showed higher ORR activity. The Pt/Co-PPy-C catalyst proceeded by an approximately four-electron pathway in acid solution. After 1000 cycles of CV, the ECSA attenuation rates of Pt/Co-PPy-C and Pt/C were 13.0% and 24.0% respectively, which means that the Pt/Co-PPy-C catalyst has higher durability. The high performance of Pt/Co-PPy-C makes it a promising catalyst for proton exchange membrane fuel cells.