Fabrication of Co@SiO₂@C/Ni submicrorattles as highly efficient catalysts for 4-nitrophenol reduction

In this paper, an extended Stöber method has been developed to fabricate a Ni²⁺-polydopamine (PDA) complex coated on Co₃[Co(CN)₆]₂@SiO₂ composites. After one-step carbonization involving the heat treatment of a Prussian blue analogue (PBA) of Co₃[Co(CN)₆]₂ cores and the PDA-Ni²⁺ shell under a nitrogen atmosphere, homogeneous Co@SiO₂@C/Ni submicrorattles were synthesized. Notably, the silica interlayer played a vital role in the formation of such Co@SiO₂@C/Ni submicrorattle structures. Without the protection of SiO₂, Co-Ni@C composites were obtained instead and aggregated seriously due to sintering at high temperature. While with the silica layer as the spacer, the obtained Co@SiO₂@C/Ni composites were not only well dispersed in the solution, but could also be adjusted in terms of the size and density of Ni nanoparticles (NPs) on the surface. Moreover, the size of core Co and surficial Ni NPs can be facilely modulated via changing the calcination temperature, which can effectively control the catalytic performance of the as-prepared nanocomposites. The as-prepared Co@SiO₂@C/Ni submicrorattles were employed as the reaction catalyst for the reduction of 4-nitrophenol (4-NP), and exhibit both superior catalytic activity and cycling stability to Co@SiO₂ and Co-Ni@C composites.