No abstract

No abstract

Many studies have been conducted on core–shell structured nanocatalysts thanks to their high thermal and physical stability. However, for a typical core–shell structure, shell thickness and pore size that affect mass transfer through the shell are difficult to control. Herein, we synthesized a different type of core–shell catalyst, in which a mesoporous silica shell encapsulates the Pd-nanocrystals-grafted-SiO2 nanobeads. With the preparation method introduced, we successfully controlled the thickness of the shell layer and generated a mesoporous texture over the shell layer. In activity tests, the production rate of hydrogen peroxide significantly increased when using the mesoporous shell catalyst over the microporous shell catalyst of similar shell thickness. The thickening of the mesoporous shell layer reduced the production rate of hydrogen peroxide. Thus, the thinner the thickness of a mesoporous shell, the more favorable in terms of pore-diffusion rate. However, the shell thickness should be adequately adjusted, because an extremely thin shell layer cannot protect the core Pd crystals from thermal agglomeration in a calcination and reduction process.

The catalytic properties of materials are determined by their electronic structures, which are based on the arrangement of atoms. Using precise calculations, synthesis, analysis, and catalytic activity studies, we demonstrate that changing the lattice constant of a material can modify its electronic structure and therefore its catalytic activity. Pd/Au core/shell nanocubes with a thin Au shell thickness of 1 nm exhibit high H2O2 production rates due to their improved oxygen binding energy (ΔE O) and hydrogen binding energy (ΔE H), as well as their reduced activation barriers for key reactions.

No abstract