Ni-Co ternary nitrides with multiple surface oxides as bifunctional oxygen electrocatalysts for metal-air batteries

The bifunctional non-noble metal catalysts based on the metal nitrides with high activity and high efficiency is very challenging for the development of high-performance metal-air batteries. Herein, a new Ni-Co ternary nitrides anchored on nitrogen-doped carbontubes (denoted as NiCoxN/CNT) is rationally designed by the thermal of corresponding hydroxide/carbontubes at low temperature, following nitridation. The synergistic effect between Ni-Co ternary nitrides (Ni4N, Co5.47N, CoN) effectively regulates the electronic configuration of the active site, thereby optimizing the chemisorption energy of the reaction intermediates, resulting in improved intrinsic catalytic activity. The result shows that NiCoxN/CNT not only exhibits excellent half-wave potential of 0.80 V for ORR but also with a low overpotential of 280 mV for OER at 10 mA cm(-2), outperforming those of cobalt mononitride and nickel mononitride. Furthermore, Zn-air batteries assembled with NiCoxN/CNT show a high specific capacity of 826.9 mA h g(-1) and excellent cycling stabilities up to 190 h in an aqueous electrolyte. More attractively, when assembled into Mg-air batteries, NiCoxN/CNT cathode realizes high power density of 112.38 mWcm(-2). Therefore, the design and construction of multiple TMNs is a new guide to break through the bifunctional catalytic activity.