Dual-Active Sites Engineering of N-Doped Hollow Carbon Nanocubes Confining Bimetal Alloys as Bifunctional Oxygen Electrocatalysts for Flexible Metal-Air Batteries.

Since the sluggish kinetic process of oxygen reduction (ORR)/evolution (OER) reactions, the design of highly-efficient, robust, and cost-effective catalysts for flexible metal-air batteries is desired but challenging. Herein, bimetallic nanoparticles encapsulated in the N-doped hollow carbon nanocubes (e.g., FeCo-NPs/NC, FeNi-NPs/NC, and CoNi-NPs/NC) are rationally designed via a general heat-treatment strategy of introducing NH3 pyrolysis of dopamine-coated metal-organic frameworks. Impressively, the resultant FeCo-NPs/NC hybrid exhibits superior bifunctional electrocatalytic performance for ORR/OER, manifesting exceptional discharging performance, outstanding lifespan, and prime flexibility for both Zn/Al-air batteries, superior to those of state-of-the-art Pt/C and RuO2 catalysts. X-ray absorption near edge structure and density functional theory indicate that the strong synergy between FeCo alloy and N-doped carbon frameworks has a distinctive activation effect on bimetallic Fe/Co atoms to synchronously modify the electronic structure and afford abundant dual-active Fe/Co-Nx sites, large surface area, high nitrogen doping level, and conductive carbon frameworks to boost the reversible oxygen electrocatalysis. Such N-doped carbon with bimetallic alloy bonds provides new pathways for the rational creation of high-efficiency energy conversion and storage equipment.