Catalytic activity and stability of nanometic Rh overlayers prepared by pulsed arc-plasma deposition and r.f. magnetron-sputtering
Catalytic activity and stability of nanometic Rh overlayers prepared by pulsed arc-plasma deposition and r.f. magnetron-sputtering
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DOI：
10.1016/j.apsusc.2017.06.310
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发表时间：
2018-01
影响因子：
6.7
通讯作者：
S. Misumi;A. Matsumoto;H. Yoshida;Tetsuya Sato;M. Machida
中科院分区：
文献类型：
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作者：
S. Misumi;A. Matsumoto;H. Yoshida;Tetsuya Sato;M. Machida
用脉冲电弧等离子体(AP)和射频熔化技术(R.F.)制备了厚度为50μm的Fe-−-Cr-−-Al金属箔，表面覆盖了7 nm厚的Rh薄膜。用磁控溅射技术比较它们的催化活性。所制备的金属箔催化剂被包裹成蜂窝结构，每平方英寸的密度为900cell，化学计量比的NO−CO−C3H6−O2反应在空速为1.2min×105h−1的条件下进行。在10℃/−1的升温过程中，蜂窝催化剂在200℃以上对NO、CO和C3H6的转化率几乎达到100%。这两种催化剂都表现出很高的循环频率，与采用传统浆料涂层制备的Rh/ZrO2粉末涂层蜂窝陶瓷相比，其循环频率接近或超过50倍。然而，当重复升温时，催化剂的催化活性随制备过程的不同而有不同程度的下降。只有溅射法制备的样品才有明显的失活现象，而AP法制备的样品没有失活迹象。钝化与形成由Fe、Cr和Al氧化物组成的钝化层有关，钝化层覆盖了表面，降低了Rh的表面浓度。与溅射制备的样品相比，AP形成的Rh覆盖层与金属箔表面的结合力很强，因此具有较好的热稳定性。
50 μm-thick Fe−Cr−Al metal foils covered by 7 nm-thick Rh overlayers were prepared by pulsed arc-plasma (AP) and r.f. magnetron sputtering technique to compare their catalytic activities. As-prepared metal foil catalysts were wrapped into a honeycomb structure with a density of 900 cells per square inches and the stoichiometric NO−CO−C3H6−O2reaction was performed at space velocity of 1.2 × 105h−1. During temperature ramp at 10 °C min−1, honeycomb catalysts showed steep light-off of NO, CO, and C3H6at above 200 °C and their conversions soon reached to almost 100%. Both catalysts exhibited high turnover frequencies close to or more than 50-fold greater compared with those for a reference Rh/ZrO2powder-coated cordierite honeycomb prepared using a conventional slurry coating. When the temperature ramping was repeated, however, the catalytic activity was decreased to the different extent depending on the preparation procedure. Significant deactivation occurred only when prepared by sputtering, whereas the sample prepared by AP showed no signs of deactivation. The deactivation is associated with the formation of passivation layers consisting of Fe, Cr, and Al oxides, which covered the surface and decreased the surface concentration of Rh. The Rh overlayer formed by AP was found to be thermally stable because of the strong adhesion to the metal foil surface, compared to the sample prepared by sputtering.