Highly active and durable carbon nitride fibers as metal‐free bifunctional oxygen electrodes for fle

Nanoscale Horizons 2(6) 333-341

http://doi.org/10.1039/C7NH00058H

Sambhaji S. Shinde, Jin‐Young Yu, Jae‐Won Song, Yoon‐Ho Nam, Dong‐Hyung Kim, Jung‐Ho Lee

Abstract

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.