Interface Engineering of CoS/CoO@N-Doped Graphene Nanocomposite for High-Performance Rechargeable Zn–Air Batteries

TLDR

Low‑cost, green fabrication of earth‑abundant electrocatalysts for ORR and OER is essential for scalable rechargeable Zn–air batteries. The study aims to rationally design the interfacial structure of a CoS/CoO@N‑doped graphene electrocatalyst to enhance charge redistribution, conductivity, and stability, thereby achieving high bifunctional ORR/OER activity and superior efficiency and durability. Using density functional theory, the authors design and synthesize CoS/CoO nanocrystals immobilized on N‑doped graphene, optimizing composition and interfacial structure to improve electronic conductivity and stability. The CoS/CoO@NGNs cathode delivers a maximum power density of 137.8 mW cm⁻², a specific capacity of 723.9 mAh g⁻¹, and 100 h cycling stability with high round‑trip efficiency, while the quasi‑solid‑state cell also exhibits excellent flexibility and performance, indicating promise for flexible/wearable electronics.

Abstract

Abstract Low cost and green fabrication of high-performance electrocatalysts with earth-abundant resources for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for the large-scale application of rechargeable Zn–air batteries (ZABs). In this work, our density functional theory calculations on the electrocatalyst suggest that the rational construction of interfacial structure can induce local charge redistribution, improve the electronic conductivity and enhance the catalyst stability. In order to realize such a structure, we spatially immobilize heterogeneous CoS/CoO nanocrystals onto N-doped graphene to synthesize a bifunctional electrocatalyst (CoS/CoO@NGNs). The optimization of the composition, interfacial structure and conductivity of the electrocatalyst is conducted to achieve bifunctional catalytic activity and deliver outstanding efficiency and stability for both ORR and OER. The aqueous ZAB with the as-prepared CoS/CoO@NGNs cathode displays a high maximum power density of 137.8 mW cm −2 , a specific capacity of 723.9 mAh g −1 and excellent cycling stability (continuous operating for 100 h) with a high round-trip efficiency. In addition, the assembled quasi-solid-state ZAB also exhibits outstanding mechanical flexibility besides high battery performances, showing great potential for applications in flexible and wearable electronic devices.