Free-standing and flexible air electrodes with long-lasting bifunctional activities for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are crucial to the development of wearable Zn-air rechargeable batteries. In this work, we synthesize a flexible air electrode consisting of 3D nanoporous N-doped graphene with trimodal shells and Ni particles through repeated chemical vapor deposition (CVD) and acidic etching processes. Our results indicate that such trimodal graphene morphology significantly enhances the active N-dopant sites and graphene-coated Ni surface, which consequentially boosts both the ORR and OER activities, as well as catalytic durability. First-principles density functional theory (DFT) calculations reveal the synergetic effects between the Ni and the N-doped graphene; namely, the Ni nanoparticles boost the bifunctional activities of the coated N-doped graphene, and in turn the graphene-covering layers enhance the stability of Ni. Thanks to the better protection from the triple graphene shells, our trimodal N-doped graphene/Ni-based Zn-air battery can be stably discharged/recharged beyond 2500 h with low overpotentials. It is reasonable to expect that such free-standing trimodal graphene/Ni would be promising in many flexible energy conversion/storage devices.

独立且灵活的空气电极对氧还原反应 (ORR) 和析氧反应 (OER) 具有持久的双功能活性，对于可穿戴锌空气可充电电池的发展至关重要。在这项工作中，我们通过重复的化学气相沉积 (CVD) 和酸性蚀刻工艺合成了由具有三峰壳和 Ni 颗粒的 3D 纳米多孔 N 掺杂石墨烯组成的柔性空气电极。我们的结果表明，这种三峰石墨烯形态显着增强了活性 N 掺杂位点和石墨烯涂覆的 Ni 表面，从而提高了 ORR 和 OER 活性以及催化耐久性。第一性原理密度泛函理论 (DFT) 计算揭示了 Ni 和 N 掺杂石墨烯之间的协同效应；即，Ni 纳米粒子增强了涂覆的 N 掺杂石墨烯的双功能活性，反过来石墨烯覆盖层增强了 Ni 的稳定性。由于三重石墨烯壳的更好保护，我们的三峰掺氮石墨烯/镍基锌空气电池可以稳定地放电/充电超过 2500 小时，且过电位较低。可以合理地预期这种独立的三峰石墨烯/镍在许多灵活的能量转换/存储设备中很有前景。