AuPd@Mesoporous SiO2: Synthesis and Selectivity in Catalytic Hydrogenation/Hydrodechlorination of p-Chloronitrobenzene
AuPd nanoparticles (NPs) protected by tetradecyl trimethyl ammonium bromide (TTAB) were coated with SiO2 through hydrolysis of tetraethylorthosilicate (TEOS). The as-synthesized AuPd@SiO2 core–shell NPs were calcined in air at 500 °C to remove TTAB and open up mesopores within the SiO2 shells. The obtained Au–PdO@m-SiO2 NPs were reduced by H2 at 300 °C to obtain AuPd@m-SiO2 NPs with AuPd NP cores (diameter: ~3 nm) and SiO2 shells (thickness: ~18 nm). Results from relevant characterization indicated that these SiO2-protected core–shell NPs were highly stable during calcination and subsequent reduction. Au@m-SiO2, Au10Pd@m-SiO2, Au5Pd@m-SiO2, AuPd5@m-SiO2, AuPd10@m-SiO2, and Pd@m-SiO2 NPs with similar core sizes and shell thicknesses were also synthesized. These samples were tested in the catalytic hydrogenation of p-chloronitrobenzene. The activity and selectivity were found to be tunable, depending on the composition of the bimetallic alloys. AuPd@m-SiO2 NPs with a 1/1 molar ratio of Au/Pd showed the highest selectivity for the hydrodechlorination of p-chloronitrobenzene.
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