Surface modification of carbon fibers with hydrophilic Fe3O4 nanoparticles for nickel-based multifunctional composites

Grafting functional components onto carbon fibers is important for designing many multifunctional composites. However, this process is often hindered by the low reactivity of carbon fibers. Hence, developing innovative grafting strategies with functional groups or nanomaterials on carbon fibers (CFs) is highly desired. Herein, we proposed a facile method to grow hydrophilic Fe3O4 NPs on non-pretreated CFs using a polyol-assisted hydrothermal method, changing hydrophobic CFs to hydrophilic. Benefiting from the hydrophilic property of CFs@Fe3O4, the resultant CFs@Fe3O4 can be successfully coated by SiO2 layer to form CFs@Fe3O4@SiO2 composites. After a hydrothermal reaction with nickel ions, the CFs@Fe3O4@nickel silicate composites were fabricated. Followed by coating polydopamine (PDA) layer and then carbonizing in N2 atmosphere, CFs@Fe3O4@SiO2-C/Ni hybrids can be finally obtained. Notably, the hydrophilic Fe3O4 NPs play a crucial role in the fabrication process, not only improving the interfacial adhesion of carbon fibers for further modification but also providing the main magnetism resource. Moreover, the density and size of Ni NPs can be tailored by tuning pyrolysis temperature. Experimental results confirm that CFs@Fe3O4@SiO2-C/Ni hybrids synthesized at 700 degrees C gave the best activity on the reduction in 4-nitrophenol, which are easy to collect and recycle due to their unique structure and good magnetic property.