Dynamic structural evolution of supported palladium–ceria core–shell catalysts revealed by in situ electron microscopy

Abstract

The exceptional activity for methane combustion of modular palladium–ceria core–shell subunits on silicon-functionalized alumina that was recently reported has created renewed interest in the potential of core–shell structures as catalysts. Here we report on our use of advanced ex situ and in situ electron microscopy with atomic resolution to show that the modular palladium–ceria core–shell subunits undergo structural evolution over a wide temperature range. In situ observations performed in an atmospheric gas cell within this temperature range provide real-time evidence that the palladium and ceria nanoparticle constituents of the palladium–ceria core–shell participate in a dynamical process that leads to the formation of an unanticipated structure comprised of an intimate mixture of palladium, cerium, silicon and oxygen, with very high dispersion. This finding may open new perspectives about the origin of the activity of this catalyst.

Recent Progress in Well‐Controlled Synthesis of Ceria‐Based Nanocatalysts towards Enhanced Catalytic Performance

“…The structure model for the forming ordered oxygen vacancies process was described in Figure 4 (empty circle). [ 28 ] They performed in situ observations in an atmospheric gas cell within this temperature range provide real-time evidence that the Pd and CeO 2 nanoparticle constituents of the core-shell structured Pd@CeO 2 participate in a dynamical process that leads to the formation of an unanticipated structure comprised of an intimate mixture of Pd, CeO 2 , and SiO 2 nanoparticles with very high dispersion. [ 39 ] Copyright 2010, IOP Publishing wileyonlinelibrary.com rectangle represented the unit cell of sesqui-oxide of the cerium oxide in the (110) orientation resulted from ordered oxygen vacancies.…”

“…The activities of nanoceria catalysts can be determined by their morphologies, oxygen vacancies, interfacial structures and the type of exposed crystal surfaces, as well as the synergistic effect exhibited by nanocomposites. [ 28 ] Therefore, it is essential to develop powerful strategies to improve the thermal stability of nanostructured ceria-based catalysts. The involved reaction mechanisms are also briefl y introduced, and eventually an outlook in the design of novel nanoceria catalysts for valuable energy applications is addressed.…”

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

“…Apart from so‐called “intelligent catalyst systems” exploiting the migration of active species into the supporting oxide with subsequent segregation, core–shell‐structures gained a lot of interest . This novel kind of nanocomposite has lately proven to be a very attractive catalyst,, and sensing material. A first set of complementary studies on the sensing behavior and catalytic performance of Pd@SnO 2 and SnO 2 @Pd core@shell nanocomposite systems has just been reported …”

Polymer-templated synthesis of hollow Pd–CeO2nanocomposite spheres and their catalytic activity and thermal stability

“…This phenomenon is caused probably by two reasons. (1) Small Pd nanoparticles would undergo a structural evolution and the Pd atoms could dissociate from Pd nanoparticles in the process of calcination at 800 °C, but this situation would not occur at 500 °C [43] .…”