Hierarchical N,P co-doped graphene aerogels framework assembling vertically grown CoMn-LDH nanosheets as efficient bifunctional electrocatalyst for rechargeable Zinc-air battery.

Abstract

Exploiting the low-cost and high-efficiency bifunctional oxygen electrocatalysts to substitute platinum-group metals is highly desirable but challenging for energy storage/conversion technologies. Herein, we develop a combined gelation/self-assemble/freeze drying process to fabricate a free-standing porous architectures through vertical anchoring two-dimensional (2D) CoMn-LDH nanosheets on three-dimensional (3D) hierarchical N,P co-doped graphene aerogels (NPGA) framework. This unique configuration endows CoMn-LDH/NPGA outstanding catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a potential difference of ca. 0.72\xa0V between the OER potential at 10\xa0mA\xa0cm-2 and the ORR potential at -3 mA cm-2, which is comparable to commercial Pt/C\xa0+\xa0IrO2 benchmarks, and therefore renders the CoMn-LDH/NPGA assembled zinc-air battery a superior rechargeable performance and cycling stability. In-depth structure-to-property correlation indicates that the prominent bifunctional activity of CoMn-LDH/NPGA are ascribed to large electrochemical active surface area, the rapid mass/charge transfers, the increased exposure and full utilization of active sites originated from the synergistic effect between the uniformly dispersed 2D CoMn-LDH nanosheets and the 3D hierarchical porous NPGA framework.