One-pot synthesis of NiFe-MOF/NiFe2O4 hollow spheres and their application as bifunctional ORR/OER electrocatalysts in Zn-air batteries

The development of bifunctional electrocatalysts to reduce the polarization loss is essential to enhance the performance of Zn-air batteries. The combination of metal-organic frameworks (MOFs) with metal or metallic compounds provides a way to integrate their merits and effectively improve their electrocatalytic performances. However, previous synthesis of MOFs/metal oxides usually involves high-temperature calcination, which makes it difficult to control their morphologies. In this work, through a ligand-insufficient and high temperature controlled solvothermal reaction, innovative NiFe-MOF/NiFe2O4 hollow nanospheres were one-pot prepared without using any shape-controlled agent or calcination process. The as-obtained NiFe-MOF/NiFe2O4 shows better ORR and OER performance than pure NiFe-MOF and NiFe2O4, suggesting a synergetic effect between NiFe-MOF and NiFe2O4. The maximum power density of the liquid Zn-air battery assembled using NiFe-MOF/NiFe2O4 as the air electrode catalyst is 158.4 mW cm−2 at 246.1 mA cm−2. This work offers fresh thoughts into designing highly efficient MOF-derived electrocatalysts.