Tailoring the nickel nanoparticles anchored on the surface of FeO@SiO spheres for nanocatalysis.

Herein, we report an efficient and universal strategy for synthesizing a unique triple-shell structured FeO@SiO@C-Ni hybrid composite. Firstly, the FeO cores were synthesized by hydrothermal reaction, and sequentially coated with SiO and a thin layer of nickel-ion-doped resin-formaldehyde (RF-Ni) using an extended Stöber method. This was followed by carbonization to produce the FeO@SiO@C-Ni nanocomposites with metallic nickel nanoparticles embedded in an RF-derived thin graphic carbon layer. Interestingly, the thin SiO spacer layer between RF-Ni and FeO plays a critical role on adjusting the size and density of the nickel nanoparticles on the surface of FeO@SiO nanospheres. The detailed tailoring mechanism is explicitly discussed, and it is shown that the iron oxide core can react with the nickel nanoparticles without the SiO spacer layer, and the size and density of the nickel nanoparticles can be effectively controlled when the SiO layer exits. The multifunctional composites exhibit a significantly enhanced catalytic performance in the reduction of 4-nitrophenol (4-NP).