Pt-based diesel oxidation catalysts were investigated for CO oxidation activity under rapid transient temperature conditions based on a realistic driving cycle, which is presently a focal point in exhaust gas aftertreatment. Experiments were performed in a microreactor setup allowing rapid heating/cooling coupled with operando Turbo X-ray absorption spectroscopy (T-XAS) and on-line product analysis by mass spectrometry. Significant differences were observed in catalyst structure and performance depending on the temperature ramp rate. Particularly for Pt/Al₂O₃, the Pt oxidation state followed a dynamic hysteresis profile during CO oxidation light-off and light-out. In contrast, in Pt–CeO₂/Al₂O₃, ceria acted as an oxygen storage buffer, reducing the width of the Pt oxidation/reduction hysteresis loop as a function of the temperature ramp rate. Ceria also supplied oxygen to the Pt surface, helping to maintain high activity during cooling down and at lower temperatures during transient conditions. This study shows the potential insights into the reaction mechanism available when considering transient temperature as an experimental condition during operando spectroscopic studies in exhaust gas catalysis. The current method is applicable to virtually any rapid transient temperature driving cycle.

中文翻译：

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在实际驾驶循环中通过操作光谱法探测的Pt颗粒的瞬态结构和催化行为

基于现实的驾驶循环，对Pt基柴油氧化催化剂在快速瞬态温度条件下的CO氧化活性进行了研究，这是目前废气后处理的重点。实验是在微反应器中进行的，可实现快速加热/冷却以及操作涡轮X射线吸收光谱（T-XAS），并通过质谱进行在线产品分析。观察到催化剂结构和性能的显着差异，这取决于温度的上升速率。特别是对于Pt / Al ₂ O ₃，在CO氧化熄灭和熄灭期间，Pt氧化态遵循动态磁滞曲线。相反，在Pt–CeO ₂ / Al ₂ O _3中氧化铈充当氧气存储缓冲液，根据温度上升速率减小Pt氧化/还原磁滞回线的宽度。Ceria还向Pt表面提供了氧气，有助于在冷却过程中以及在瞬态条件下在较低温度下保持较高的活性。这项研究表明，当在废气催化的操作光谱学研究中将瞬态温度作​​为实验条件时，可以对可用的反应机理进行深入研究。当前的方法几乎适用于任何快速瞬态温度驱动周期。