Rich atomic interfaces between sub-1 nm RuO_x clusters and porous Co₃O₄ nanosheets boost oxygen electrocatalysis bifunctionality for advanced Zn-air batteries

The practical use of Zn-air batteries (ZABs) is strongly dependent on the availability of bifunctional oxygen electrocatalysts that should have high activity and durability for both oxygen evolution/reduction reactions (OER/ORR) in alkaline solution. Herein, we report the design of a new Ru-based bifunctional catalyst characterized with rich atomic interfaces through the in-situ growth of sub-1nm RuO_x clusters on the surface of porous Co₃O₄ nanosheets with 4.1 ​wt% Ru loaded. Such unique architecture ensures the creation of high-energy interfacial Ru-O-Co bond that allows fine tuning of the electronic structure of both Ru and Co. The as-prepared catalyst exhibits superior oxygen electrocatalysis bifunctionality, indicated by an ultralow potential gap of 0.71 ​V between the potential of OER at 10 ​mA ​cm^-2 (1.51 ​V) and the half-wave potential for ORR (0.80 ​V). Remarkably, rechargeable ZAB with such electrocatalyst demonstrates not only high rate performance (50 ​mA ​cm⁻²) and power density (150 ​mW ​cm^-2), but also superior round-trip efficiency (68.4%, after 250 ​h). X-ray photoelectron and Raman spectroscopy reveal that the active sites for ORR/OER are mainly the unsaturated trivalence Ru in RuO_x clusters, and the formed interfacial Ru-O-Co bond can avoid the dissolution of RuO_x in alkaline electrolyte, holding great potential in implementation of long-life rechargeable ZABs.