CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

Abstract

Encapsulation of small noble metal nanoparticles has received attention owing to the resulting highly increased stability and high catalytic activity and selectivity. Among the types of inert metal oxides, CeO 2 is unique. It is inexpensive and highly stable, and, more importantly, the unique electronic configuration gives it a strong capability to provide active oxygen. The method of fabricating CeO 2 -encapsulated noble metal nanocatalysts is determined by the requirements of the application. In this review, we first describe the various types of encapsulated noble metals and then the current developments of synthesis in detail, including the types of hybrid nanostructures and successful synthetic strategies. The following section, concerning catalytic applications, is divided into three topics: anti-sintering capabilities, catalytic activities and selectivities. We hope that this review of the recent achievements and the proposed strategy for addressing the emerging challenges will inspire further developments in this research area. NPG Asia Materials (2015) 7, e179; doi:10.1038/am.2015.27; published online 8 May 2015 INTRODUCTIONNoble metal catalysts have received much attention in the past decade because of their unique chemical and physical properties, and they have been widely applied in industrial use. [1][2][3][4][5][6][7][8][9][10] With the help of noble metal catalysts, environmental friendly catalysis resulting in the decreased production of pollutants, waste minimization and new synthetic routes that circumvent modern synthetic techniques such as Sonogashira-, Heck-and Miyaura-Suzuki-type reactions can be easily realized. 11-15 However, for most technologically important chemical processes, noble metal catalysts spontaneously aggregate and grow to reduce the surface energy, which limits the catalysts' lifetime and efficiency. The ultra-high prices of noble metals have also seriously limited their further development. Because of the development of modern industry, there remains a critical need for robust, simple and readily controllable routes to fabricate highly active, stable and recyclable nanocatalysts.To maximize the catalytic performance of noble metals and reduce the quantity used, it is necessary to load the active centers on a substrate. [16][17][18][19][20] A suitable substrate not only provides a high surface area to stabilize small nanoparticles (NPs) under long-term catalysis but also renders hybrid junctions with rich redox reactions on the two-phase interface. With the development of synthetic techniques in nanoscience, small noble metal NPs, especially atomically precise nanoclusters/metal oxide hybrid nanostructures, have been successfully fabricated very recently, and these materials exhibit remarkable enhanced catalytic activity and selectivity. [21][22][23] However, this simple loading form cannot meet the growing demand for the stability, because the noble metal catalysts contain numerous exposed surfaces

Achieving the Trade‐Off between Selectivity and Activity in Semihydrogenation of Alkynes by Fabrication of (Asymmetrical Pd@Ag Core)@(CeO2 Shell) Nanocatalysts via Autoredox Reaction

“…Our group has continuously focused on the development of clean and efficient synthesis of noble metal@CeO 2 core@shell nanostructures . Inspired by our gradual advances, we here report a new modified autoredox reaction combined with the seeded growth strategy to cleanly obtain CeO 2 ‐encapsulated asymmetric Pd@Ag core@shell metal nanostructures.…”

l‐Arginine‐Triggered Self‐Assembly of CeO2 Nanosheaths on Palladium Nanoparticles in Water

“…Our research group has continuously focused on the potential of ceria (CeO 2 )o wing to its numerous oxygen vacancy defects and high oxygen-storage capacity. [6][7][8][9][10] Cerium is highly earth-abundant and can readily convert between the III and IV oxidation states. [11] These properties have made CeO 2 the key oxygen-storage component of the three-way catalyst used in automotive catalytic converters for the elimination of engine-exhaust pollutants.…”

l‐Arginine‐Triggered Self‐Assembly of CeO2 Nanosheaths on Palladium Nanoparticles in Water

“…Our research group has continuously focused on the potential of ceria (CeO 2 ) owing to its numerous oxygen vacancy defects and high oxygen‐storage capacity . Cerium is highly earth‐abundant and can readily convert between the III and IV oxidation states .…”