Electronic modulation induced by coupling RuO2 with electron-donating Co3O4 for high-active and long-life rechargeable Zn-air batteries

Electronic-state modulation strategy offers great potential in designing RuO₂-based bifunctional-electrocatalysts for rechargeable Zn-air batteries (ZABs). Various three-dimensional (3D) transition metal oxides are attempted to couple with RuO₂ for constructing an appropriate RuOM interface. This work aims to construct Co₃O₄-RuO₂ heterostructures on carbon sheets (Co₃O₄/RuO₂/NCNS) for boosting electronic transfer and regulation. Experiments and theoretical calculations identify the electronic transfer from Co₃O₄ to RuO₂ that modulates the electronic structure of metal surfaces/interfaces. Specifically, it leads to the increase in Co³⁺ content, electron-rich state at RuO₂ surface and electronic accumulation at interfaces. Moreover, this electronic-state modulation optimizes the d-band center in Co₃O₄/RuO₂ that lowers the reaction barriers and endows interfaces as the biggest contributor to oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance. The Co₃O₄/RuO₂/NCNS shows a quite low potential difference of 0.62 V and remarkable durability for ORR/OER. Co₃O₄/RuO₂/NCNS-assembled ZABs exhibit an excellent specific capacity of 818.3 mA h g⁻¹ and a superior lifespan over 750 h.