Yolk-shell ZIF-8@ZIF-67 derived Co3O4@NiCo2O4 catalysts with effective electrochemical properties for Li-O2 batteries

Abstract Metal−organic frameworks (MOFs) have attracted researchers’ attention because of its unique adjustable structure, large open space and high porosity. Herein, we design a yolk-shell catalyst of Co3O4@NiCo2O4, which selects ZIF-8@ZIF-67 materials with rhombic dodecahedron structure as the template, and is coated with NiCo2O4. Compared with the pure Co3O4, Co3O4@NiCo2O4 composite exhibits excellent ORR and OER performance as the adjustable structure, abundant active sites and open space. Furthermore, the discharge capacity of Co3O4@NiCo2O4 catalyst is 11672.8 mA h g−1, while Co3O4 cathode is 8636.3 mA h g−1, even at 600 mA g−1 current density, Co3O4@NiCo2O4 cathode retains the capacity retention of 48.2%, much higher than that of Co3O4, i.e., 21.6%. As for the cycle test, Co3O4@NiCo2O4 composite has much long cycle life of 280 cycles. In contrast, the Co3O4 electrode only has 77 cycles.