Composition-adjustable Mo₆Co₆C₂/Co@carbon nanocage for enhanced oxygen reduction and evolution reactions

Bifunctional oxygen electrocatalysts that hold outstanding activity and stability are highly crucial for the development of efficient rechargeable Zn-air batteries. Herein, cobalt-molybdenum-based bimetallic carbide and cobalt nanoparticles embedded N-doped carbon nanocages are synthesized via the pyrolysis of functionalized zeolitic imidazolate framework precursor originated from zeolitic imidazolate framework sequentially coated with polydopamine and phosphomolybdic acid. Furthermore, we revealed the composition-performance relationship based on the exploration of bifunctional performance on the pyrolysis products. More importantly, the synergy of multiple active sites with hollow structure gives the prepared catalyst a low overpotential (284 mV) for oxygen evolution reaction and high half-wave potential (0.865 V) for oxygen reduction reaction, besides an excellent bifunctional durability. Furthermore, the prepared catalyst as a cathode electrocatalyst grants the assembled rechargeable Zn-air batteries a high open-circuit voltage, power density, specific capacity, and remarkable charge-discharge cycle stability. This work provides a strategy for the integration and active-adjustment of bifunctional catalyst and its potential applications in water splitting and other catalytic reactions.