Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), Engesserstr. 20, 76131, Karlsruhe, Germany.
Institut de Recherches sur la Catalyse et l'Environnement de Lyon, UMR 5256, CNRS, Université Claude Bernard Lyon 1, Université de Lyon, 2 Avenue Albert Einstein, 69626, Villeurbanne, France.
Angew Chem Int Ed Engl. 2017 Oct 9;56(42):13078-13082. doi: 10.1002/anie.201707842. Epub 2017 Sep 18.
A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures (<500 °C) and exploited to enhance the catalytic activity of Pt/CeO -based exhaust gas catalysts. Redispersion of platinum in an oxidizing atmosphere already occurred at 400 °C. A protocol with reducing pulses at 250-400 °C was applied in a subsequent step for controlled Pt-particle formation. Operando X-ray absorption spectroscopy unraveled the different extent of reduction and sintering of Pt particles: The choice of the reductant allowed the tuning of the reduction degree/particle size and thus the catalytic activity (CO>H >C H ). This dynamic nature of Pt on ceria at such low temperatures (250-500 °C) was additionally confirmed by in situ environmental transmission electron microscopy. A general concept is proposed to adjust the noble metal dispersion (size, structure), for example, during operation of an exhaust gas catalyst.
在中低温（<500°C）条件下，我们发现 Pt 纳米颗粒在氧化铈表面的动态结构行为会在还原/氧化条件下发生变化，并利用这一特性来提高基于 Pt/CeO 的废气催化剂的催化活性。在 400°C 时，Pt 就已经在氧化气氛中发生了再分散。随后，我们采用在 250-400°C 之间施加还原脉冲的方案来进行后续步骤，以实现对 Pt 颗粒的可控形成。原位 X 射线吸收光谱揭示了 Pt 颗粒的不同还原和烧结程度：还原剂的选择可以调节还原程度/颗粒尺寸，从而调节催化活性（CO>H >C H ）。在如此低的温度（250-500°C）下，氧化铈上 Pt 的这种动态特性还通过原位环境透射电子显微镜得到了进一步证实。我们提出了一种通用概念来调整贵金属的分散度（尺寸、结构），例如，在废气催化剂的运行过程中。
