Dual-active-site hierarchical architecture containing NiFe-LDH and ZIF-derived carbon-based framework composite as efficient bifunctional oxygen electrocatalysts for durable rechargeable Zn-air batteries

Abstract The rational design and synthesis of efficient and durable bifunctional electrocatalysts for oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) is significant yet challenging for rechargeable Zn-air batteries. Up to now, most attention has been focused on the ORR performance, but the disproportion of OER proficiencies results in poor cycling capabilities and energy waste during charging process. Herein, a dual-active-site hierarchical composite (Co-NC@LDH) is constructed by anchoring high OER-active NiFe layered double hydroxide (NiFe-LDH) nanosheets on the surface of ORR-active ZIF-derived carbon-based framework. This design fully utilizes their advantages and synergistic effects, such as good conductivity, hierarchical structure, ORR-active sites of Co, N-codoped carbon (Co-NC) substrate and OER-active sites of NiFe-LDH, to optimize bifunctional catalytic performance and durability in Zn-air batteries. The Co-NC@LDH demonstrates a lower overpotential of 819 mV than single component Co-NC (893 mV), NiFe-LDH (1178 mV) and noble-metal catalysts (957 mV for Pt/C and 1118 mV for RuO2) in alkaline media. Impressively, a high peak power density (107.8 mW cm−2) and excellent durability (over 300 h) are exhibited by Zn-air batteries based on Co-NC@LDH as electrocatalyst. This work provides a facile, low-cost and environmental-friendly strategy to synthesize bifunctional catalysts for efficient and durable zinc-air batteries.