Palladium Nanoparticles Embedded in Yolk–Shell N-Doped Carbon Nanosphere@Void@SnO₂ Composite Nanoparticles for the Photocatalytic Reduction of 4-Nitrophenol

Herein, a novel visible-light-driven yolk–shell nanoreactor has been fabricated, called as Pd/N–Cs@SnO2, which is consisted of movable nitrogen-doped carbon sphere (N–Cs) yolk, interlayer void, mesoporous tin oxide (SnO2) shell, and encapsulated palladium nanoparticles (Pd NPs). The obtained yolk–shell Pd/N–Cs@SnO2 nanoreactor can serve as an excellent catalyst in the visible-light-driven photocatalytic reduction of 4-nitrophenol (4-NP). More importantly, Pd/N–Cs@SnO2 exhibits a remarkable superior activity and higher reusability than core–shell Pd@SnO2 and yolk–shell Pd/N–Cs@mSiO2 nanoreactors. The fabulous character of Pd/N–Cs@SnO2 nanoreactor is attributed to (I) the mesostructured SnO2 shell provides a large surface area for the collection of light as well as the anchoring of Pd to avoid aggregating or leaching; (II) the interlayer void space improves the light absorption by multiple scattering, as well as favors the contact of active sites with reactants in the photocatalytic reactions; (III) the N–Cs allow more permeable visible-light absorption, and accelerate the photoexcited electrons transportation from SnO2 semiconductor to Pd NPs to suppress the electron–hole recombination. This enriches the electron density of Pd NPs surface and then facilitates the photocatalytic reduction of 4-NP. Both the structural advantages and enhanced synergy of Pd/N–Cs@SnO2 nanoreactor make it to be an efficient and stable photocatalyst, which can open an avenue for designing photocatalysts in a board range of organic reactions.