As the global demand for efficient renewable energy storage intensifies, zinc–air batteries (ZABs) face critical bottlenecks from sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics and poor cycling stability at air electrodes. Now, researchers from Soochow University, Hainan University, University of Seoul, and Yonsei University, led by Professor Zhe Wang, Professor Liang Li, and Professor Seong-Ju Hwang, have presented a breakthrough heterogeneous catalyst that bridges the gap between single-atom precision and nanocluster synergy for next-generation bifunctional oxygen electrocatalysis.
Why This Catalyst Matters
Traditional dual-atom catalysts (DACs) typically suffer from the intrinsic limitation of hosting only one type of metal active site, which constrains their ability to simultaneously achieve high catalytic activity and long-term durability for both ORR and OER. The novel FeN4–Ru6–NiN4@PCA overcomes this limitation by engineering atomically isolated FeN4/NiN4 dual sites coupled with adjacent Ru₆ nanoclusters on a 3D porous carbon aerogel, combining atomic-level precision with multiscale electronic modulation for exceptional bifunctional performance and stability.
Innovative Design and Mechanism
The catalyst is synthesized through a directional freeze-drying and two-step pyrolysis strategy, where cellulose nanofibers act as the structural "skeleton," graphene oxide serves as "cement," and ZIF-derived porous carbon nanocages entwine with carbon nanotubes to form a highly graphitized 3D honeycomb matrix. Density functional theory calculations reveal that the Ru₆ nanoclusters induce pronounced electron redistribution across the FeN4 and NiN4 dual sites, optimizing electron transfer to the key oxygen intermediate (OH) at the rate-determining steps. The Fe center serves as the ORR active site with weakened OH adsorption (0.519 eV barrier vs. 0.574 eV without Ru6), while the Ni center drives OER with enhanced OH* interaction (0.718 eV vs. 0.858 eV), creating a synergistic bifunctional architecture.
Outstanding Performance
FeN4–Ru6–NiN4@PCA delivers a high ORR half-wave potential of 0.874 V and achieves OER at merely 1.58 V at 10 mA cm-2, with a remarkably low bifunctional voltage gap of 0.706 V—surpassing benchmark Pt/C and RuO2 catalysts. The material exhibits characteristic stability signatures: 96% current retention after 12 h of ORR operation, minimal E1/2 degradation of only 9 mV after 20,000 CV cycles, and superior methanol tolerance compared to commercial Pt/C. When employed as the air cathode in aqueous ZABs, the device achieves an exceptional peak power density of 197.76 mW cm-2 and maintains stable cycling for over 2000 h (2000 cycles), dramatically outperforming Pt/C + RuO2 counterparts that fail after merely 95 h.
Applications and Future Outlook
When integrated into flexible solid-state ZABs with a polyacrylamide organohydrogel electrolyte, the system delivers a maximum power density of 53.4 mW cm-2 and stable cycling up to 80 h. Serially connected flexible cells successfully charge mobile phones and power LED displays, demonstrating real-world deployability. This work establishes a new paradigm for heterogeneous catalyst design coupling dual-atom sites with nanoclusters, opening promising avenues for next-generation energy storage systems combining high activity, exceptional durability, and practical flexibility.
Stay tuned for more groundbreaking research from this collaborative team at Soochow University, Hainan University, University of Seoul, and Yonsei University!