Tuning the Structure of Platinum Particles on Ceria InSitu for Enhancing the Catalytic Performance of Exhaust Gas Catalysts

A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures (< 500 degrees C) and exploited to enhance the catalytic activity of Pt/CeO2-based exhaust gas catalysts. Redispersion of platinum in an oxidizing atmosphere already occurred at 400 degrees C. A protocol with reducing pulses at 250-400 degrees 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-2 > C3H6). This dynamic nature of Pt on ceria at such low temperatures (250-500 degrees 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.