Co₂P@N,P-codoped carbon nanofiber as a free-standing air electrode for Zn-air batteries : synergy effects of CoNₓ satellite shells

• Main Authors: Gao, Jingchang, Wang, Jinming, Zhou, Lijun, Cai, Xiaoyi, Zhan, Da, Hou, Mingzhen, Lai, Linfei
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2021
• Subjects: Science::Physics; Cobalt Phosphide; Zn−air Battery
• Online Access: https://hdl.handle.net/10356/151252
• Institution: Nanyang Technological University

Here, a free-standing electrode composed of cobalt phosphides (Co₂P) supported by cobalt nitride moieties (CoNₓ) and an N,P-codoped porous carbon nanofiber (CNF) in one-step electrospinning of environmentally friendly benign phosphorous precursors is reported. Physiochemical characterization revealed the symbiotic relationship between a Co₂P crystal and surrounding nanometer-sized CoNₓ moieties embedded in an N,P-codoped porous carbon matrix. Co₂P@CNF shows high oxygen reduction reaction and oxygen evolution reaction performance owing to the synergistic effect of Co₂P nanocrystals and the neighboring CoNₓ moieties, which have the optimum binding strength of reactants and facilitate the mass transfer. The free-standing Co₂P@CNF air-cathode-based Zn-air batteries deliver a power density of 121 mW cm⁻² at a voltage of 0.76 V. The overall overpotential of Co₂P@CNF-based Zn-air batteries can be significantly reduced, with low discharge-charge voltage gap (0.81 V at 10 mA cm⁻²) and high cycling stability, which outperform the benchmark Pt/C-based Zn-air batteries. The one-step electrospinning method can serve as a universal platform to develop other high-performance transition-metal phosphide catalysts benefitting from the synergy effect of transition nitride satellite shells. The free-standing and flexible properties of Co₂P@CNF make it a potential candidate for wearable electronic devices.