Silver palladium bimetallic core-shell structure catalyst supported on TiO2 for toluene oxidation
Silver palladium bimetallic core-shell structure catalyst supported on TiO2 for toluene oxidation
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TiO2负载银钯双金属核壳结构催化剂用于甲苯氧化
DOI：
10.1016/j.apsusc.2018.08.023
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发表时间：
2018-12-31
影响因子：
6.7
通讯作者：
Zhou, Junli
中科院分区：
文献类型：
--
作者：
Li, Yongfeng;Liu, Fangfang;Zhou, Junli
结果表明，以TiO 2为载体的银钯核壳结构催化剂（Ag@Pd/TiO 2）在低钯负载量下具有较高的甲苯氧化净化活性。采用电化学置换法在Ag纳米颗粒上包覆Pd，制备了Ag@Pd催化剂。透射电子显微镜（TEM）、高分辨率TEM和扫描TEM与能量色散谱仪证实催化剂具有核-壳构型，并且是球形的，平均直径尺寸约为9.0 nm。紫外-可见吸收光谱和选区电子衍射进一步证明了核壳结构中Ag和Pd的紧密接触和不同的电负性导致电子从Ag核转移到Pd壳，从而增加了Pd原子周围的局域电子密度。此外，X射线光电子能谱表明，Ag@Pd/TiO 2催化剂中Pd活性位上电子密度的增加，可显著增强O-2与反应物的化学吸附，进一步促进Pd-0金属向PdO氧化态的相转变，最终维持甲苯氧化反应中Pd-0-PdO协同机理的正常运行。因此，与单金属Pd/TiO 2催化剂相比，所制备的Ag@Pd/TiO 2核壳结构催化剂虽然钯负载量仅为Pd/TiO 2的1/3，但整体上具有更高的甲苯氧化活性。高催化氧化活性和低钯负载量使Ag@Pd/TiO 2成为用于VOC净化的有前途的催化剂。
We show that silver palladium bimetallic core-shell structure catalysts supported on TiO2 substrate (Ag@Pd/TiO2) are highly active with a low palladium loading for toluene purification in oxidation reaction. The Ag@Pd catalysts were synthesized by galvanic replacement of Pd coating on Ag nanoparticles. Transmission electron microscopy (TEM), high-resolution TEM, and scanning TEM with energy dispersive spectrometer confirmed that the catalysts have a core-shell configuration, and are spherical in shape with an average diameter size of about 9.0 nm. The UV-vis absorption spectroscopy and selected area electron diffraction further proved that the intimate contact and different electronegativity of Ag and Pd in core-shell structure result in electrons transferring from Ag core to Pd shell, which increases local electron density around Pd atom. In addition, X-ray photoelectron spectroscopy reveals that such an increase of electron density on Pd active site in Ag@Pd/TiO2 catalyst can substantially strengthen the chemisorption with reactant of O-2, further promote the phase transformation from Pd-0 metal to PdO oxidation state, and finally maintain the normal operation of Pd-0-PdO synergic mechanism during toluene oxidation reaction. Hence, compared to monometallic Pd/TiO2 catalyst, the as-prepared bimetallic core-shell Ag@Pd/TiO2 catalyst exhibits greatly higher toluene oxidation activity as a whole although its palladium loading value is just one third of Pd/TiO2. The high catalytic oxidation activity with a low Pd loading makes the Ag@Pd/TiO2 a promising catalyst for use in VOCs purification.