Probing BaO Doping Effect on the Structure and Catalytic Performance of Pd/CexZr1–xO2 (x = 0.2–0.8) Catalysts for Automobile Emission Control

详细信息    查看全文

• 作者：Linyan Yang ; Xue Yang ; Renxian Zhou
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：February 11, 2016
• 年：2016
• 卷：120
• 期：5
• 页码：2712-2723
• 全文大小：767K
• ISSN：1932-7455

文摘

Pd/CeO₂-ZrO₂-BaO (Pd/CZB) catalysts with 5.0 wt % BaO and different CeO₂/ZrO₂ molar ratio were synthesized. The modification with BaO significantly promotes the catalytic activity of HC and NO_x conversions when the molar ratio of CeO₂ to ZrO₂ is 2/1, because the substitution of Ce^x+/Zr⁴⁺ ions by Ba²⁺ promotes the formation of oxygen vacancy as revealed by XRD refinement analysis results and improves the mobility of active oxygen as a result of electronic and structural modifications. Among the Ba-doped catalysts, the crystalline form of the CZB supports gradually transform from cubic and pseudocubic to stable tetragonal phase as the increase of ZrO₂ content. Meanwhile, the Raman results show that addition of moderate ZrO₂ promotes the formation of structural defects, resulting in higher OSC and NO_x storage efficiency. On the other hand, the introduction of moderate ZrO₂ facilitates the dissociative adsorption of NO and promotes the deep oxidation of HC. Therefore, Pd/CZB catalysts with CeO₂/ZrO₂ molar ratio of 3/1–1/1, especially Pd/CZB21, show a much better catalytic activity of HC and NO_x eliminations and a wider dynamic operation window. Zr-rich catalysts present worse catalytic activity of CO oxidation compared with Ce-rich catalysts, which is mainly arising from the decreased amount of active sites. After thermal aging treatment, Zr-rich catalysts (CeO₂/ZrO₂ < 1) undergo less severe deterioration of the catalytic activity compared with Ce-rich catalysts (CeO₂/ZrO₂ ≥ 1) as a result of better thermostability, and Pd/CZB11-a presents the best catalytic performance and widest dynamic operation window.