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

Abstract

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.

Exploiting Synergies in Catalysis and Gas Sensing using Noble Metal‐Loaded Oxide Composites

“…The latter allowed to grow the Pt‐particles and manipulate the Pt dispersion and consequently the catalyst activity. This enables to fine‐tune the Pt particle size for an optimum in CO oxidation activity …”

“…The latter allowed to grow the Pt-particles and manipulate the Pt dispersion and consequently the catalysta ctivity.T his enables to fine-tune the Pt particles ize for an optimum in CO oxidation activity. [14] Very small chemical changes occurring at the active noble metal phase during catalysis or sensing whichc annot be observedv ia conventionalX AS might be addressedw ith HERFD-XAS. [74a,b, 81] Based on hard X-rays the technique does not impose any other special requirements towards the materials to investigate.…”

Origin of the High CO Oxidation Activity on CeO2 Supported Pt Nanoparticles: Weaker Binding of CO or Facile Oxygen Transfer from the Support?

“…Ganzler et al. reported that small Pt clusters supported on CeO 2 are much more active than atomically dispersed Pt and a size of ∼1.4 nm was reported to be optimal . The origin of the high CO oxidation activity on ceria supported Pt nanoparticles was proposed to be due to highly active sites at the Pt−CeO 2 interface.…”

Transformation of a Pt–CeO2 Mechanical Mixture of Pulsed‐Laser‐Ablated Nanoparticles to a Highly Active Catalyst for Carbon Monoxide Oxidation

“…There, the oxidation state of platinum, its dispersion, and microstructure substantially depend on the reaction mediumu sed for the catalyst treatment. [24,25,[33][34][35][36][37] Av ariety of platinum states is formed through as trongc hemical interaction with the support (SMSI effect), so that platinum can be in cationic states and in different metallicc luster species. [37][38][39][40][41][42][43][44][45] The interaction of metallic platinum particlesw ith ceria, studied in many publications,w as shown to increase the catalytic activity per platinum atom in comparison, for example, with the Pt/Al 2 O 3 catalyst.…”