Engineering zinc ferrite nanoparticles in a hierarchical graphene and carbon nanotube framework for improved...

This work presents the successful fabrication of a composite made of multi-walled carbon nanotubes and reduced graphene oxide, with immobilized zinc ferrite nanoparticles (ZnFe₂O₄@CNT/RGO). Functionalized CNT (F-CNT) and few-layered graphene oxide (GO) not only works as a precursor for the hierarchical CNT/RGO skeleton, but also participates in the redox reactions with zinc and ferrous ions to synthesize the intermediate products ZnO@CNT and FeOOH@RGO, respectively. A ZnO@CNT/FeOOH@RGO composite is obtained by through the spontaneous assembly process between the above intermediate species, and the final ZnFe₂O₄@CNT/RGO composite is fabricated through a simple solid-state reaction. The ZnFe₂O₄@CNT/RGO composite delivers a reversible capacity of about 1250 mAh·g^-1 after 100 cycles at a low current of 200 mA·g^-1, about 1100 mAh·g^-1 after 300 cycles at a high current of 1000 mA·g^-1. It has been verified that an increase in battery performance can be attributed to the engineered hierarchical CNT/RGO supportive skeleton, the generation of smaller electrochemically active ZnO and Fe₂O₃ crystals, and pseudocapacitive behavior. The sample design and preparation method in this work are both economical and scalable, allowing further development and use in other applications.