Yashima Masatomo, Falk Lena K L, Palmqvist Anders E C, Holmberg Krister
Department of Applied Surface Chemistry, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
J Colloid Interface Sci. 2003 Dec 15;268(2):348-56. doi: 10.1016/j.jcis.2003.07.041.
Mixtures of nanosized platinum and palladium particles have been prepared by reduction of salt-containing microemulsion droplets using hydrazine as the reducing agent. To avoid possible negative effects of the presence of sulfur compounds during the preparation the microemulsion was made using the sulfur-free nonionic polyoxyethylene 4 lauryl ether surfactant. Transmission electron microscopy showed that the as-prepared mixtures contained crystalline platinum particles of fairly homogeneous size (20 to 40 nm) with adsorbed amorphous palladium particles 2 to 5 nm in size. Catalyst samples were prepared by depositing the nanoparticles on a gamma-Al(2)O(3) support followed by heating in air at 600 degrees C. Alloyed particles of platinum and palladium with sizes ranging from 5 to 80 nm were obtained during the heating. The majority of the particles had the fcc structure and their compositional range was dependent upon the Pt:Pd molar ratio of the microemulsion. A catalyst prepared from a microemulsion with a 20:80 Pt:Pd molar ratio showed the highest catalytic activity for CO oxidation, while pure platinum and palladium catalysts showed higher sulfur resistance. These results differ from the performance of conventional wet-impregnated catalysts, where a 50:50 Pt:Pd molar ratio resulted in the highest catalytic activity as well as the highest sulfur resistance.
通过使用肼作为还原剂还原含盐水微乳液滴，制备了纳米尺寸的铂和钯颗粒混合物。为避免制备过程中硫化合物存在可能产生的负面影响，使用无硫的非离子聚氧乙烯4月桂基醚表面活性剂制备微乳液。透射电子显微镜显示，所制备的混合物包含尺寸相当均匀（20至40纳米）的结晶铂颗粒，以及吸附的尺寸为2至5纳米的非晶态钯颗粒。通过将纳米颗粒沉积在γ-Al(2)O(3)载体上，然后在600℃空气中加热来制备催化剂样品。加热过程中获得了尺寸范围为5至80纳米的铂和钯合金颗粒。大多数颗粒具有面心立方结构，其组成范围取决于微乳液的Pt:Pd摩尔比。由Pt:Pd摩尔比为20:80的微乳液制备的催化剂对CO氧化表现出最高的催化活性，而纯铂和钯催化剂表现出更高的抗硫性。这些结果与传统湿浸渍催化剂的性能不同，在传统湿浸渍催化剂中，Pt:Pd摩尔比为50:50时催化活性最高且抗硫性也最高。
