Durability Investigation of Carbon Supported Platinum Electrocatalysts Synthesized by Microwave Polyol Method

摘要

Due to the simple and rapid processes, the microwave-assisted polyol method has received much attention as a promising technique for preparation of metal nanoparticles with small particle sizes and narrow size distributions. The platinum (Pt) nanoparticles supported on carbon black, currently the most widely used electrocatalysts in proton exchange membrane fuel cells, tend to degrade under extended operating conditions, probably due to the agglomeration/dissolution of Pt particles or the corrosion of the carbon support. Therefore, in the present study the microwaveassisted polyol technique was utilized to prepare the Pt nanoparticles supported on two nanoscale carbon supports, carbon nanotubes (CNTs) and Vulcan XC-72R (VXR), with a Pt loading of 20 wt. %. The ethylene glycol was acted as both solvent and reducing agent, and the pH value of the reaction solution was adjusted to 7 by KOH solution. The mixture was placed in a household microwave oven (Tatung, 800 W) and heated for 90 s. One commercial Pt/C catalyst (E-TEK) was used for comparison. The results show that Pt nanoparticles were dispersed uniformly on the surface of different carbon supports. The mean particle sizes of Pt were 3.1 刡 0.33, 3.9 刡 0.26 and 2.9 刡 0.47 nm for Pt/CNTs, Pt/VXR and Pt/C catalysts. The microwave synthesized Pt nanoparticles supported on CNTs and VXR formed a face-centered cubic structure. The TGA profiles indicated that Pt/CNTs performed better oxidation resistance. The estimations of the electrochemical surface area (ESA) were 55, 58 and 64 m2/g for Pt/CNTs, Pt/VXR and Pt/C catalysts, but the degradation of the ESA after 600 cycles were 16, 21 and 28 %, respectively. The data suggested that the ESA of Pt/CNTs or Pt/VXR prepared by microwave method was comparable to the commercial Pt/C and the Pt/CNTs exhibited better durability than other samples.