A novel bimetallic RuFe nanocluster to enable highly efficient oxygen reduction in zinc-air batteries

Zinc-air batteries (ZABs) have the advantages of high energy density and safety but their large-scale application is hindered by sluggish kinetics of four-electron aqueous O2 redox reactions. Widely used Ruthenium (Ru)-based catalysts possess intrinsic oxygen evolution catalytic activity but suffer from insufficient oxygen reduction reaction (ORR) performance. Herein, to optimize the ORR activity of Ru-based catalyst, an iron (Fe)-coordinated, bimetallic RuFe cluster is constructed and homogeneously dispersed within nitrogen (N)-doped carbon layers (denoted as RuFe@NC). Benefitting from the optimized ORR activity and more active site exposure, the RuFe@NC exhibits superior ORR activity with a half wave potential (E1/2) of 0.88 ​V higher than that of Pt/C (0.82 ​V). Accordingly, the RuFe@NC-based ZAB outperforms the Pt/C ​+ ​IrO2-based device, presenting a reduced polarization of 0.7 ​V and an enhanced cycling lifetime of 50 ​h at 10 ​mA ​cm−2. Moreover, the optimized structural design ultralow Ru loading (0.013 mgRu cm−2) overcomes the cost barriers and demonstrates its high practicality. This bimetallic RuFe nanocluster opens a new way for future design of more efficient and stable catalytic systems.