Facile Synthesis of Vertical Layered Double Hydroxides Nanosheets on Co@Carbon Nanoframes as Robust Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

The development of efficient and low-cost bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative but remains challenging in rechargeable zinc-air batteries. Herein, a metal oxidation-assisted approach is developed for the facile synthesis of a highly efficient bifunctional catalyst (Co@NC@LDHs) which is composed of layered double hydroxides (LDHs) nanosheets in situ vertically grown on the surface of hollow carbon nanoframes encapsulating Co nanoparticles (Co@NC). Specifically, the vertical LDHs distributing on the carbon surface ensure the maximized number of accessible active sites and the interaction between LDHs with the carbon matrix. The hierarchically structured bifunctional Co@NC@LDHs display an overpotential of 0.33 V at 10 mA cm-2 for OER and a half-wave potential of 0.88 V for ORR. The potential gap (Delta E) of Co@NC@LDHs is calculated to be 0.68 V, outperforming the mixed Pt/C + RuO2 catalysts (Delta E = 0.77 V), manifesting its superior bifunctional electrocatalysis performance. Moreover, the Zn-air batteries based on Co@NC@LDHs electrocatalyst exhibit a high peak power density (185.2 mW cm-2) and excellent durability (5.0 mA cm-2 over 500 h). This work may provide a facile strategy for the fabrication of LDHs on carbon substrate, acting as efficient catalysts for broad energy-related applications. A facile metal oxidation-assisted strategy is developed to prepare a bifunctional electrocatalyst (Co@NC@LDHs), which exhibits robust bifunctional electrocatalytic performance for oxygen reduction reaction and oxygen evolution reaction, and Co@NC@LDHs-assembled zinc-air batteries display a low charge-discharge gap, high power density, and superior durability.image (c) 2023 WILEY-VCH GmbH