The design of flexible, highly energetic, and durable bifunctional oxygen electrocatalysts is indispensable for rechargeable metal–air batteries. Herein we present a simple approach for the development of carbon nitride fibers co-doped with phosphorus and sulfur, grown in situ on carbon cloth (PS-CNFs) as a flexible electrode material, and demonstrate its outstanding bifunctional catalytic activities toward ORR and OER compared to those of precious metal-based Pt/C and IrO₂ on account of the dual action of P and S, numerous active sites, high surface area, and enhanced charge transfer. Furthermore, we demonstrate the flexibility, suitability, and durability of PS-CNFs as air electrodes for primary and rechargeable Zn–air batteries. Primary Zn–air batteries using this electrode showed high peak power density (231 mW cm⁻²), specific capacity (698 mA h g⁻¹; analogous energy density of 785 W h kg⁻¹), open circuit potential (1.49 V), and outstanding durability of more than 240 h of operation followed by mechanical recharging. Significantly, three-electrode rechargeable Zn–air batteries revealed a superior charge–discharge voltage polarization of ∼0.82 V at 20 mA cm⁻², exceptional reversibility, and continuous charge–discharge cycling stability during 600 cycles. This work provides a pioneering strategy for designing flexible and stretchable metal-free bifunctional catalysts as gas diffusion layers for future portable and wearable renewable energy conversion and storage devices.

中文翻译：

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高活性和耐用的氮化碳纤维，用作柔性Zn-air电池的无金属双功能氧电极

柔性，高能且耐用的双功能氧电催化剂的设计对于可充电金属-空气电池是必不可少的。本文中，我们提出了一种简单的方法来开发掺有磷和硫的氮化碳纤维，并在碳布（PS-CNFs）上原位生长作为柔性电极材料，并证明了其对ORR和OER的出色的双功能催化活性。到贵金属Pt / C和IrO ₂由于P和S的双重作用，许多活性位点，高表面积和增强的电荷转移。此外，我们证明了PS-CNF作为一次和二次充锌空气电池的空气电极的灵活性，适用性和耐用性。使用该电极的一次锌空气电池显示出高峰值功率密度（231 mW cm ^-2），比容量（698 mA hg ^-1；模拟能量密度为785 W h kg ^-1），开路电势（1.49 V），并具有超过240小时的出色耐用性，随后进行机械充电。值得注意的是，三电极可充电Zn-空气电池在20 mA cm ^{-2的条件下}显示出约0.82 V的极佳充电-放电电压极化，出色的可逆性以及600次循环中的连续充放电循环稳定性。这项工作为设计柔性和可拉伸的无金属双功能催化剂作为气体扩散层提供了开创性的战略，以用于未来的便携式和可穿戴式可再生能源转换和存储设备。