Surfactant-free Pd@pSiO2 yolk–shell nanocatalysts for selective oxidation of primary alcohols to aldehydes

Combined high catalytic activity and thermal stability were achieved with a well-structured, surfactant-free Pd@porous SiO2 yolk–shell nanostructure, resulting from the entirely exposed Pd core particles and highly porous silica shells. Pd@SiO2 core–shell nanoparticles were synthesized by a water-in-oil microemulsion method for direct silica coating of as-prepared tiny Pd nanoparticles. Hydrothermal etching and subsequent high thermal treatment generated large pores in the silica shells and facilitated complete removal of surfactants around the core particles. The surfactant-free Pd@pSiO2 yolk–shell nanoparticles efficiently catalyzed the oxidation of benzyl alcohol as well as that of various substituted benzyl alcohols.