High activity bifunctional non-noble electrocatalysts, targeting both ORR and OER, are rationally designed by integrating the merits of both NiFe₂O₄ quantum dots and carbons nanotubes (CNTs) (NiFe₂O_4(QDs)/CNTs), which possesses large specific surface area (584 m² g⁻¹), abundant NiFe₂O₄ quantum dots and superior conductivity. Specially, the mechanism for the formation of quantum dots in relation to Fe/Ni ratio and the corresponding activity of ORR and OER are studied carefully. Consequently, NiFe₂O_4(QDs)/CNTs exhibits superior bifunctional oxygen electrocatalytic activities with the lowest the potential difference (ΔE) of 0.9 V, outperforming well-known commercial Pt/C and IrO₂, directly demonstrating the advantages of quantum dots catalysts on providing more effective actives sites and adsorption-desorption sites to promote oxygen reaction kinetics. NiFe₂O_4(QDs)/CNTs, as high-performance catalyst used in liquid and flexible metal-air batteries, realize high power density, high specific capacity, long-term rechargeability (over 800 h), and extremely low charge-discharge voltage gaps (only 0.62 V) in ambient atmosphere. Furthermore, the metal-air batteries with flexible configuration effectively prevent the migration of Zn²⁺/Mg²⁺, the production of carbonate and the hydrogen evolution reaction. Density functional theory calculations further illustrate that the NiFe₂O_4(QDs) on CNT has a very active ORR and OER site at the interface Ni site. The work offers prospects for the rational design of quantum dots containing composites to achieve their practicalities in next generation of metal-air batteries.

通过兼顾NiFe ₂ O ₄量子点和碳纳米管（NiFe ₂ O _4（QDs） / CNTs）的优点，合理设计了针对ORR和OER的高活性双功能非贵金属电催化剂。比表面积（584m ² g ^-1），丰富的NiFe ₂ O ₄量子点和优异的电导率。特别地，仔细研究了与Fe / Ni比有关的量子点形成机理以及ORR和OER的相应活性。因此，NiFe ₂ O _4（QDs）/ CNTs具有优异的双功能氧电催化活性，最低电势差（ΔE）为0.9 V，优于知名的商用Pt / C和IrO ₂，直接证明了量子点催化剂在提供更有效的活性位点和吸附方面的优势-解吸位促进氧反应动力学。NiFe ₂ O _4（QDs） / CNTs，作为液体和柔性金属-空气电池中使用的高性能催化剂，可实现高功率密度，高比容量，长期可充电性（超过800小时）以及极低的充放电环境大气中的电压间隙（仅0.62 V）。此外，具有灵活配置的金属空气电池可有效防止Zn ²⁺ / Mg迁移²⁺，碳酸盐的产生和氢的释放反应。密度泛函理论计算进一步表明，CNT上的NiFe ₂ O _4（QDs）在Ni界面处具有非常活跃的ORR和OER位置。这项工作为合理设计包含复合材料的量子点提供了前景，以实现其在下一代金属空气电池中的实用性。