反胶束法制备直接甲醇燃料电池Pt-Sn/C催化剂及其表征

Preparation and Performance of Carbon Supported Platinum-Tin Catalyst for Direct Methanol Fuel Cell by Reverse Micelle Method

在水/AOT/环己烷反胶束体系中,制备了Pt-Sn/C催化剂,研究了不同ω(反胶束溶液中水与表面活性剂的物质量之比)值对Pt-Sn粒径的影响.并采用TEM,XRD,XPS,循环伏安等技术对其进行表征.TEM结果表明合成的Pt-Sn纳米颗粒为球形,在碳载体表面均匀分布,粒径分布窄,平均粒径为2.7nm.Pt-Sn颗粒尺寸随着ω的增加而增大.XRD结果表明该催化剂中Pt具有面心立方结构且没有与Sn形成合金.XPS结果表明在该催化剂中,Pt主要以零价态存在.在甲醇溶液中的循环伏安扫描结果表明,甲醇氧化峰电位和峰电流随着ω的增加而减小,说明反胶束方法可以通过控制颗粒尺寸,从而影响催化剂的电氧化活性.相对于商用Pt-Ru/VulcanXC-72(20wt%,E-TEK公司),该催化剂具有较低的峰电势以及较高的If/Ib(循环伏安曲线中正向扫描峰电流与反向扫描峰电流的比值),这表明用此方法制备的Pt-Sn/C催化剂具有较好的抗中毒能力.

Carbon supported catalyst Pt-Sn/C was synthesized in reverse micelle solution of water/AOT/ cyclohexane [AOT： bis-（2-ethylhexyl）sodium sulfosuccinate, （aerosol-OT）] and characterized by TEM, XRD, XPS and cyclic voltammetry （CV） techniques. TEM results showed that the Pt-Sn bimetallic particles were well dispersed on the carbon support with narrow size distribution and regular spherical shape. The average size of the particles prepared is about 2.7 nm, and the particle size was increased with the increase of ω value （water-surfactant molar ratio）. XRD results show that Pt has fcc crystalline structure and did not alloyed with Sn. XPS results showed that the surface of the catalyst prepared was mainly covered by metallic platinum, Sn（Ⅱ） and/or Sn（Ⅳ） species. CV results show that the methanol electrooxidation activity was decreased with the increase of ω value, and the catalyst prepared has lower peak current potential and higher If/Ib [the ratio of the forward anodic peak current density （If） to the backward anodic peak current density （Ib） obtained from CV] than commercial catalyst of Pt-Ru/Vulcan XC-72 （20 wt% Pt-Ru, E-TEK company）.