In Situ Exfoliating and Generating Active Sites on Graphene Nanosheets Strongly Coupled with Carbon Fiber toward Self-Standing Bifunctional Cathode for Rechargeable Zn-Air Batteries

The self-standing electrode nanomaterials with highly effective bifunctional electrocatalysis for oxygen reduction and evolution reactions (ORR/OER) are important for practical applications in metal-air batteries. Herein, a defectenriched and pyridinic-N (PN) dominated bifunctional electrocatalyst with novel core-shell architecture (DN-CP@G) is successfully fabricated by in situ exfoliating graphene from carbon paper followed by high temperature ammonia treatment. Benefitting from its strongly coupled core-shell structure, abundant defective sites and high-content PN dopants, the DN-CP@G displays an excellent electrocatalytic (ORR and OER) activity and stability in alkaline media, which are comparable to commercial Pt/C and Ir/C catalysts. The experiment, and theoretical calculations demonstrate that the electrocatalytic activities of carbon materials strongly depend on their defective sites and PN dopants. By directly using DN-CP@G as a self-standing electrode, the assembled zinc-air battery demonstrates a high discharge performance and outstanding long-term cycle stability with at least 250 cycles, which is much superior to the mixed Pt/C and Ir/C electrodes. Remarkably, the DNCP@G based all-solid-state battery also reveals a good discharge and cycle performance. A facile and cost-efficient approach to prepare highly effective bifunctional self-standing electrode is provided by in situ generation of active sites on carbon support for metal-air batteries.