Abstract
A series of Pt-based alloys consisting of Pt, Ru and Co were used as cathodic catalysts for proton exchange membrane fuel cell (PEMFC). The catalysts were synthesized and deposited on multiwalled carbon nanotubes (MWCNTs) directly by chemical reduction using NaBH4 as reducing agent. The atomic ratio of Pt and Ru was fixed at 4:1. By adding Co to the alloy, it was expected that the performance of catalysts in the cathodic oxygen reduction reaction may be improved. MWCNTs were used as the support of catalysts. However, the original surface was inert and not easy to be deposited with catalysts. By reaction with HNO3 and H2SO4, the surface of MWCNTs could generate defects or organic functional groups so that catalysts could be deposited and dispersed on the surface. The physical and chemical properties of modified MWCNTs were analyzed by BET, Raman, and FTIR. The composition and properties of all catalysts were analyzed by XRD, TEM, ICP-MS, CV, and MEA test. The result shows that all of the Pt-based nanoparticles except the Pt4Ru1Co5 could be prepared by reduction with NaBH4 and they all aggregated on the surface defects of MWCNTs. The particle sizes of Pt4Ru1 and Pt4Ru1Co5 catalysts were both around 4 nm. The maximum output powers of Pt4Ru1/CNT (pH=10) and (pH=11) were 0.21 W/cm2 and 0.19 W/cm2, respectively, while that of E-TEK was 0.33 W/cm2. The maximum powers of Pt/CNT and Pt4Ru1Co5/CNT were both below 0.05 W/cm2. The difference of performance may result from the dispersion of particles, particle size, and the Pt content in the catalysts. The characterization and analyses of all home-made catalysts are also discussed.