New route for the preparation of Pd and PdAu nanoparticles using photoexcited Ti-containing zeolite as an efficient support material and investigation of their catalytic properties.
New route for the preparation of Pd and PdAu nanoparticles using photoexcited Ti-containing zeolite as an efficient support material and investigation of their catalytic properties.
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DOI：
10.1021/la9015367
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
K. Mori;Yuki Miura;S. Shironita;H. Yamashita
中科院分区：
文献类型：
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作者：
K. Mori;Yuki Miura;S. Shironita;H. Yamashita
本文提出了一种在紫外光照射下，以含单中心钛氧化物的沸石分子筛（TS-1）为载体，合成纳米钯粒子的简单而独特的方法。通过光辅助沉积（PAD）方法，Pd前体可以从Pd的水溶液直接沉积在沸石框架内的光激发四面体配位的Ti氧化物部分上。随后用H2还原产生具有窄尺寸分布的纳米级Pd金属颗粒（PAD-Pd/TS-1）。通过XAFS和TEM分析的表征表明，金属颗粒的大小取决于制备方法，并且与常规制备的浸渍催化剂相比，在光沉积催化剂上形成较小尺寸的Pd纳米颗粒。PAD还从PdCl 2和HAuCl 4的混合物的水溶液提供PdAu纳米颗粒。在常压下用H2和O2直接合成过氧化氢（H2 O2）的反应中，催化剂的活性强烈依赖于制备方法和Au原子的存在。在此，在UV光照射下将PdAu沉积到TS-1部分上对于上述反应是最有效的。本发明的催化体系的适用性通过在H2和O2存在下使用PAD-Pd/TS-1的苯酚的一锅反应而突出，其中Pd纳米颗粒和框架内的隔离的Ti氧化物部分分别参与H2 O2的形成和苯酚的氧化。
A simple and unique route to synthesize nanosize Pd particles using a zeolite support including a single-site Ti oxide moiety (TS-1) under UV-light irradiation has been developed. By the photoassisted deposition (PAD) method, a Pd precursor can be deposited directly on the photoexcited tetrahedrally coordinated Ti oxide moiety within the zeolite frameworks from an aqueous solution of Pd. The subsequent reduction with H2 generates the nanosized Pd metal particles with a narrow size distribution (PAD-Pd/TS-1). Characterization by XAFS and TEM analysis revealed that the size of the metal particles depends on the preparation methods and that the smaller sizes of Pd nanoparticles were formed on the photodeposited catalysts compared with the conventionally prepared impregnated catalysts. PAD also provides PdAu bimetallic nanoparticles from an aqueous solution of mixture of PdCl2 and HAuCl4. The catalytic activities in the direct synthesis of hydrogen peroxide (H2O2) using H2 and O2 gases under atmospheric pressure were strongly dependent on the preparation method and the presence of Au atoms. Here, both deposition of PdAu onto the TS-1 moiety under UV-light irradiation was the most efficient for the above reaction. The applicability of the present catalytic system is highlighted by the one-pot reaction of phenol using PAD-Pd/TS-1 in the presence of H2 and O2, in which both Pd nanoparticles and isolated Ti oxide moieties within the frameworks participate in the formation of H2O2 and oxidation of phenol, respectively.