Activated palladium deposited on defect-rich carbon and cobalt oxide composite materials as bi-functional catalysts for stable rechargeable Zn–air battery

Using defect-rich carbon with slightly oxidized palladium and oxygen-vacancy-induced cobalt oxide from ZIF-67 improves the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are crucial reactions for air cathodes of desirable Zn–air batteries. Electron-deficient palladium and free electron at oxygen vacancies facilitate the adsorption of oxygen species, thereby enhancing the OER performance. Moreover, hybridization of defect-rich N-doped carbon with catalytically active Pd nanoparticles advances the ORR activity. Through a delicate synthetic method, we synthesized the bi-functional catalysts, Pd and CoOx embedded in defect-rich and N-doped carbon materials (Pd/CoOx/d-NC), for rechargeable Zn–air battery. Pd/CoOx/d-NC exhibits superior activities and robust durability for both the ORR and OER. In addition, it shows higher performance than the benchmark Pt/C + IrO2 when applied to the Zn–air battery. The robust durability for ORR and OER of Pd/CoOx/d-NC results in charge–discharge cycle stability. The outstanding catalytic activities and stable cycle life of Pd/CoOx/d-NC verifies its potential as a catalyst for air cathode in practical Zn–air battery application.