Rich atomic interfaces between sub-1 nm RuOx 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-lam RuOx 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 RuOx clusters, and the formed interfacial Ru-O-Co bond can avoid the dissolution of RuOx in alkaline electrolyte, holding great potential in implementation of long-life rechargeable ZABs.