Designing of nanocatalysts to understand the role of interfaces

Abstract

In heterogeneous catalysts, the active metal is supported on an oxide to accelerate the catalytic reaction. The factors affecting catalytic performance are mainly the size, shape, and composition of the active metal, but the oxide support also has a great impact. In particular, various studies have been conducted to show that the properties of the interface between metal and oxide have a great influence on the catalytic reaction. Supporting noble metals such as Pt, Au, Pd, Rh, and Ru on reducing oxide unexpectedly increases catalytic activity due to strong metal support interaction in catalytic reactions such as CO oxidation, methanol oxidation, and water-gas shift reaction. Nanocatalysts made of nanoparticles are essential to clearly identify factors affecting catalytic properties by precisely controlling the desired size, shape, composition, and interface. In situ characterization and theoretical calculations to investigate surface changes that occur during reactions have led to great advances in understanding catalytic phenomena at the atomic level. Herein, various studies on how the interfacial properties of nanocatalysts with size and shape controlled at the nanoscale affect the catalytic reaction are introduced. As a reducible oxide, CeO2 easily forms the oxygen vacancies and transfers an oxygen at the interface to increase reactivity. The effect of CeO2 facets is verified through the CO oxidation reaction by loading Au nanoparticles into CeO2 cubes composed of (100) planes and CeO2 octahedrons composed of (111) planes. Through a combinatorial approach of catalytic experiments and density functional theory calculations, we study how the size of metal nanoparticles and the oxide surface facets systematically affect the catalytic activity of a series of metal nanoparticle-supported CeO2 catalysts. In addition, the role of the interface is investigated without using the noble metals by controlling the number of interfaces in the well-defined Co3O4-CeO2 nanostructures.