Surface Reorganization on Electrochemically-Induced Zn-Ni-Co Spinel Oxides for Enhanced Oxygen Electrocatalysis

Herein, we highlight redox-inert Zn²⁺ in spinel-type oxide (Zn_X Ni_1-X Co₂ O₄ ) to synergistically optimize physical pore structure and increase the formation of active species on the catalyst surface. The presence of Zn²⁺ segregation has been identified experimentally and theoretically under oxygen-evolving condition, the newly formed V_Zn -O-Co allows more suitable binding interaction between the active center Co and the oxygenated species, resulting in superior ORR performance. Moreover, a liquid flow Zn-air battery is constituted employing the structurally optimized Zn_0.4 Ni_0.6 Co₂ O₄ nanoparticles supported on N-doped carbon nanotube (ZNCO/NCNTs) as an efficient air cathode, which presents remarkable power density (109.1 mW cm^-2 ), high open circuit potential (1.48 V vs. Zn), excellent durability, and high-rate performance. This finding could elucidate the experimentally observed enhancement in the ORR activity of Zn_X Ni_1-X Co₂ O₄ oxides after the OER test.