Synthesis of ZIF/CNT nanonecklaces and their derived cobalt nanoparticles/N-doped carbon catalysts for oxygen reduction reaction

Development of high-performance electrocatalyst for oxygen reduction reaction is imperative to address the issues of energy and environment. Zeolitic imidazolate frameworks (ZIFs)/carbon nanotubes (CNTs) composites have been regarded as a promising precursor to fabricate efficient catalysts. However, it is challenging to synthesize ZIF/CNT composites with unique structure and controllable compositions. Herein, a CNT-directing assembly strategy is developed to synthesize ZIF/CNT nanonecklaces with unique structure and tunable Zn/Co ratios. The oxidized CNTs are employed as a structure-directing agent to prepare one-dimensional nanonecklaces. The ratios of Co/Zn in the ZIF can be adjusted from 0 to 8:2 by simply changing the amount of metal precursors. After carbonization and acid leaching, Co nanoparticles are embedded in the graphitization carbon matrix. Zn species are removed completely and produce plenty of nanopores in the carbon framework. Such ZIF/CNT nanonecklaces derived carbon composites are further used as a catalyst for oxygen reduction reaction, which show high onset potential (0.92 V) and high limiting current density (5.31 mA cm⁻² at 0.30 V). This work provides a new synthesis strategy for the fabrication metal/carbon composited catalysts.