Super-assembled carbon nanofibers decorated with dual catalytically active sites as bifunctional oxygen catalysts for rechargeable Zn-air batteries

Both porous structure and dispersed active sites play key roles in improving non-precious-metal electrocatalysts performance, because of the enhanced mass transport and electron transfer as well as more effective electrocatalysis, respectively. However, the agglomeration of active sites and the weak interaction between active sites and carrier severely weakens the bifunctional catalytic activity of non-precious-metal catalysts. Herein, bifunctional electrocatalysts with the full exposure of nanoparticles of controllable sizes are successfully designed and prepared through super-assembling of electrospun carbon nanofibers with zeolitic imidazole frameworks (ZIFs) and subsequent calcination. Owing to the high surface area, large pore volume, and abundant exposed active sites, the resulting catalysts exhibit a large half-wave potential (0.89 V) for oxygen reduction reaction (ORR) and a low potential (1.62 V) at the current density of 10 mA/cm² for oxygen evolution reaction. In addition, when assembled into a home-made Zn-air battery with alkaline electrolyte, this catalyst displays a more superior charge–discharge cycle durability (1256 cycles in 10 mA/cm²) and a higher peak power density of 115 mW/cm² than commercial Pt/C + IrO₂ catalysts. This simple and efficient super-assembly strategy will open up the new process for fabricating diverse electrocatalysts for various performance.