Controlled synthesis of Pd–NiO@SiO2 mesoporous core–shell nanoparticles and their enhanced catalytic performance for p-chloronitrobenzene hydrogenation with H2

In this work, Pd–NiO@SiO2 core–shell mesoporous nanocatalysts with ~4 nm Pd–NiO heteroaggregate nanoparticle cores and ~17 nm mesoporous silica shells were successfully synthesized by a sol–gel method. The surfactant-capped PdNi alloy nanoparticles were coated with SiO2 through hydrolysis of tetraethylorthosilicate to obtain PdNi@SiO2 nanoparticles, and the mesoporous Pd–NiO@SiO2 core–shell nanocatalysts were formed after removal of surfactants by calcination at 500 °C and subsequent H2 reduction at 200 °C. The characterization results by XRD, TEM and BET revealed that Pd–NiO@SiO2 nanocatalysts were highly stable with the maintenance of intact core–shell structures under high-temperature thermal treatments. The Pd–NiO@SiO2 nanocatalysts illustrated a superior catalytic performance for p-chloronitrobenzene hydrogenation with H2 to the control Pd@SiO2 nanocatalysts. The catalytic performance enhancement of Pd–NiO@SiO2 nanocatalysts is ascribed to the strong interaction between Pd and NiO in the cores, where the interfaces may be beneficial for hydrogenation reactions.