LAUSR

Hierarchical carbon microtube@nanotube (CMT@CNT) core–shell nanostructure is successfully synthesized. The CMT@CNT shows superior electrocatalytic activity for oxygen reduction reaction and oxygen evolution reaction. A mass-loading independent high performance for zinc–air battery is achieved on the CMT@CNT. Zinc–air batteries (ZABs) hold tremendous promise for clean and efficient energy storage with the merits of high theoretical energy density and environmental friendliness. However, the performance of practical ZABs is still unsatisfactory because of the inevitably decreased activity of electrocatalysts when assembly into a thick electrode with high mass loading. Herein, we report a hierarchical electrocatalyst based on carbon microtube@nanotube core–shell nanostructure (CMT@CNT), which demonstrates superior electrocatalytic activity for oxygen reduction reaction and oxygen evolution reaction with a small potential gap of 0.678 V. Remarkably, when being employed as air–cathode in ZAB, the CMT@CNT presents an excellent performance with a high power density (160.6 mW cm −2 ), specific capacity (781.7 mAhg Zn −1 ) as well as long cycle stability (117 h, 351 cycles). Moreover, the ZAB performance of CMT@CNT is maintained well even under high mass loading (3 mg cm −2 , three times as much as traditional usage), which could afford high power density and energy density for advanced electronic equipment. We believe that this work is promising for the rational design of hierarchical structured electrocatalysts for advanced metal-air batteries.