NiFe Layered Double Hydroxide Nanoparticles on Co,N-Codoped Carbon Nanoframes as Efficient Bifunctional Catalysts for Rechargeable Zinc-Air Batteries

The future large-scale deployment of rechargeable zinc-air batteries requires the development of cheap, stable, and efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this work, a highly efficient bifunctional electrocatalyst is prepared by depositing 3-5 nm NiFe layered double hydroxide (NiFe-LDH) nanoparticles on Co,N-codoped carbon nanoframes (Co,N-CNF). The NiFe-LDH/Co,N-CNF electrocatalyst displayed an OER overpotential of 0.312 V at 10 mA cm(-2) and an ORR half-wave potential of 0.790 V. The outstanding performance of the electrocatalyst is attributable to the high electrical conductivity and excellent ORR activity of Co,N-CNF, together with the strong anchoring of 3-5 nm NiFe-LDH nanoparticles, which preserves active sites. Inspired by the excellent OER and ORR performance of NiFe-LDH/Co,N-CNF, a prototype rechargeable zinc-air battery is developed. The battery exhibited a low discharge-charge voltage gap (1.0 V at 25 mA cm(-2)) and long-term cycling durability (over 80 h), and superior overall performance to a counterpart battery constructed using a mixture of IrO2 and Pt/C as the cathode. The strategy developed here can easily be adapted to synthesize other bifunctional CNF-based hybrid electrodes for ORR and OER, providing a practical route to more efficient rechargeable zinc-air batteries.