Robust bifunctional oxygen electrocatalyst with a “rigid and flexible” structure for air-cathodes

The development of highly active air-cathodes with robust stability and a low price is of crucial significance for rechargeable Zn–air batteries and remains a great challenge. Herein, for the first time, we report a “rigid and flexible” material consisting of three-dimensional (3D) porous nickel-manganese oxide (Ni₆MnO₈) coupled with 1D ultrathin Au nanowires (Au-NWs) as an efficient bifunctional oxygen electrocatalyst, adopting α-naphthol-Au(III) as a precursor of Au-NWs and pre-formed Ni₆MnO₈ as a support. Ni₆MnO₈ acts not only as a robust carbon-free support that is stable in alkaline electrochemical conditions, but also as a highly active component for the oxygen evolution reaction (OER), while flexible Au-NWs contribute to the excellent oxygen reduction reaction (ORR) activity and act as a flexible conductive electronic network. The coupling of Ni₆MnO₈ and Au-NWs plays a complementary role in the two types of oxygen electrocatalytic reactions. Accordingly, their advantages have been optimally harnessed while overcoming their deficiencies. Moreover, a Zn–air battery assembled with such a rigid and flexible air-cathode has lower charge and discharge overpotentials and a higher cyclic stability than those with a mixed Pt/C+RuO₂ catalyst.