Fabrication of copper-cobalt heterostructures confined inside N-doped carbon nanocages for long-lasting Zn-air batteries

Delicate construction of sophisticated bimetallic nanostructures provides a favorable way to boost the efficiency of bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which is critical to the fabrication of rechargeable Zn-air batteries. Herein, hetero-structured Cu/Co93Cu7 nanoparticles confined inside N-doped carbon nanocages (denoted as Cu/Co93Cu7@NC NCs) are fabricated through a facile "MOF-in situ-reduction and in situ-growth-MOF" strategy. Benefiting from the unique hollow architecture and superior intrinsic activity of the optimized interfaces, the as-prepared catalyst displays an appealing electrocatalytic performance including a positive half-wave potential (E-1/2) of 0.88 V for ORR and a low OER over-potential of 262 mV at 10 mA cm(-2). Theoretical calculations further disclose the key role of the rationally designed Co/Cu/N-doped carbon heterostructures, which significantly reduces the energy barrier for *OOH formation and eventually promotes the ORR. Rechargeable Zn-air batteries assembled with the Cu/Co93Cu7@NC NCs exhibit a large specific capacity of 884.9 mAh g(Zn)(-1) and a maximum power density of 225.9 mW cm(-2). Moreover, the assembled batteries are stable for 1000 h during the long-term charge and discharge cycling, demonstrating the great promise for practical applications.