Regulation Of Shape, Structure And Electrochemical Properties Of Pd And Pd/Au Core-Shell Metal Nanoparticles

As an important electrochemical process, oxygen reduction reaction (ORR) has wide applications in various fields such as fuel cells and wasterwater treatment. Currently a lot of studies have been carried out for the research and development of novel and efficient catalysts for the ORR, most of which are Pt-bsed catalysts. However, the scarcity and costness of Pt-based catalysts restrict their applications in commercial use. Moreover, the Pt-based catalysts are aslo easy to be passivated by the intermediates in ORR. Considering that Pd has a similar properties with Pt and it is chearper and easier to be obtained, Pd-base catalysts are thought to be the best substitute for the Pt-based ones. Based on this, the present study has successfully prepared single-Pd nanoparticles with different morphologies using chemical redaction method and Pd@Au core-shell nanoparticles using seed-growth method. The morpholy and structure of these nanoparticles have been characterized using X-ray diffraction(XRD), scanning electron microscope(SEM) and transmitting electron microscope(TEM). Cubic Pd nanoparticles have a more uniform and regular morpholoy distribution both than that of spherical Pd and Pd@Au core-shell nanoparticles. The electrochemical measurements has shown that though cubic Pd nanoparticles has a better catalytic activity for ORR than that of spherical ones, it is worse than that of Pd@Au core-shell ones.The initial carbon nanotubes (CNTs) have been acidified by a mixture of sulfuric and nitric acid in order to make them functionalized and so it is easier for them to support nanoparticles. The cubic Pd nanoparticles and Pd@Au core-shell ones have been loaded respectively on these acidified CNTs using impregnation method. Both Pd/CNTs and Pd@Au/CNTs composite catalysts have been succsessfully prepared. The study has shown that these coposite catalysts have significantly improved electrochemical catalytic activities compared to those metallic nanoparticles.