A "trimurti" heterostructured hybrid with an intimate CoO/CoxP interface as a robust bifunctional air electrode for rechargeable Zn–air batteries

Abstract

The development of robust and cost-effective bifunctional oxygen electrocatalysts is of significant importance for the widespread implementation of Zn–air batteries yet remains an immense challenge, which calls for the molecular-level manipulation of active species as well as morphology engineering to accelerate the reversible oxygen reaction dynamics. Herein, a “trimurti” heterostructured cobalt-based hybrid is designed by a facile, one-step phosphorization of layered Co-hexamine metal–organic frameworks. The synergistic effect between cobalt phosphides (Co₂P and CoP) and cobalt oxide significantly boosts the electrocatalytic activity of the oxygen redox reaction. Besides, the hierarchically porous structure promotes the accessibility of active species and smooth electron/reactant transportation. Due to these attributes, the as-developed electrocatalyst outperforms the state-of-art non-noble metal catalysts and even noble metal benchmarks with a half-wave potential of 0.86 V for the ORR and an overpotential of 0.37 V at 10 mA cm⁻² for the OER. Furthermore, an appealing catalytic performance is also demonstrated in an assembled Zn–air battery, which displays a lower voltage gap of 0.86 V and improved cyclability of 202 h. This work not only affords a competitive bifunctional oxygen electrocatalyst for Zn–air batteries but also highlights the synergetic effect from heterointerfaces in electrocatalysis.