Exploiting a High-Performance “Double-Carbon” Structure Co<sub>9</sub>S<sub>8</sub>/GN Bifunctional Catalysts for Rechargeable Zn–Air Batteries
Xiaoling Sun, Qiaojuan Gong, Yunxia Liang, Mingjie Wu, Nengneng Xu, Pengni Gong, Shuhui Sun, Jinli Qiao
Abstract
Rational synthesis of bifunctional electrocatalysts with high performance and strong durability is highly demanded rechargeable metal–air battery. In this work, ZIF-derived Co9S8/C coated with conductive graphene nanosheet (Co9S8/GN) was synthesized by a simple solvothermal method and formed a stable double-carbon structure. As expected, the prepared Co9S8/GN catalyst exhibits a high catalytic activity (ΔE: 0.88 V) and long-term durability toward both oxygen reduction reaction and oxygen evolution reaction (ORR and OER), which is even superior to the Pt/C + Ir/C mixture (0.91 V). In addition, the Zn–air battery with the Co9S8/GN catalyst showed higher power density (186 mW cm–2) and more stable charge–discharge cycling performances (2000 cycles) than the Pt/C + Ir/C (118 mW cm–2). Based on these analysis results, the favorable catalytic performance of ORR/OER should be illustrated by the following reasons: (i) large specific surface area and unique mesoporous structure, providing abundant active sites; (ii) good conductivity, accelerating the electrons transfer; and (iii) the unique stable “double-carbon” structures (metal–S–C–C), preventing the agglomeration of metal sulfide, building new quick transfer pathway, and forming the strong electron coupling ability and synergistic effect.