Key Takeaways & Executive Findings
- •• • The Fe/FeIr-NC catalyst achieves an ORR half-wave potential of 0.91 V and an OER overpotential of 250 mV at 10 mA cm−2, yielding a bifunctional gap (ΔE) of 0.57 V—the lowest reported for single- and dual-atom catalysts, directly addressing the activity trade-off that limits conventional bifunctional electrocatalysts. • • In a flexible fiber zinc-air battery, the catalyst delivers a peak power density of 3920 W kg−1, a 1.4-fold increase in energy efficiency, and a 2.6-fold extension in cycle life compared to the commercial Pt/C + IrO2 benchmark, demonstrating practical viability for wearable power sources. • • The spatial decoupling of Fe single atoms (ORR) and Fe–Ir dual-atom pairs (OER) enables independent optimization of each reaction, overcoming the thermodynamic scaling relationship that typically compromises bifunctional performance. • • The catalyst is synthesized on a nitrogen-doped carbon matrix, providing a scalable platform for atomically dispersed metal catalysts, with potential for extension to other metal combinations and applications beyond zinc-air batteries.
Abstract
The sluggish kinetics of oxygen reduction and evolution reactions (ORR/OER) at the air electrode impede the practical deployment of fiber zinc-air batteries (FZABs) for wearable electronics. Conventional bifunctional catalysts suffer from an inherent activity trade-off due to the distinct mechanisms of ORR and OER. Here, we propose a spatial decoupling strategy to overcome this limitation by engineering isolated Fe single atoms and Fe–Ir dual-atom pairs on a nitrogen-doped carbon matrix (Fe/FeIr-NC). In this architecture, Fe single atoms serve as ORR centers, while Fe–Ir pairs with tunable spacing are tailored for OER, enabling complete functional separation and independent optimization. The catalyst exhibits an ORR half-wave potential of 0.91 V and an OER overpotential of 250 mV at 10 mA cm−2, yielding a record-low bifunctional gap (ΔE = 0.57 V) that outperforms all reported single- and dual-atom catalysts. A flexible fiber zinc-air battery based on this catalyst delivers a peak power density of 3920 W kg−1, along with a 1.4-fold increase in energy efficiency and a 2.6-fold extension in cycle life compared to the commercial Pt/C + IrO2 benchmark. This work not only breaks the traditional activity trade-off in bifunctional catalysis but also offers a promising route toward high-performance power sources for wearable electronics.
1. Introduction
The escalating demand for wearable electronics necessitates energy storage systems that combine high performance with flexibility and lightweight form factors. Among candidates, zinc-air batteries (ZABs) offer a compelling theoretical energy density of 1086 Wh kg−1, cost-effectiveness, and inherent safety. However, their practical deployment, particularly in fiber-shaped configurations (FZABs), is hindered by the sluggish kinetics of the oxygen reduction and evolution reactions (ORR/OER) at the air electrode. These reactions proceed through distinct pathways with different rate-determining steps, creating a thermodynamic scaling relationship that imposes an inevitable trade-off: optimizing activity for one reaction compromises the other. This fundamental bottleneck has limited the performance of bifunctional electrocatalysts, preventing FZABs from achieving the efficiency and longevity required for commercial wearable electronics.
Atomically dispersed metal catalysts, including single-atom and dual-atom sites, have emerged as promising candidates due to their high atomic utilization and tunable electronic structures. However, conventional designs often attempt to balance ORR and OER on the same active site, which inherently limits performance. The present work introduces a spatial decoupling strategy that assigns distinct catalytic functions to separate atomic sites: Fe single atoms are dedicated to ORR, while Fe–Ir dual-atom pairs are engineered for OER. This architectural innovation allows independent optimization of each reaction, breaking the traditional activity trade-off. The resulting Fe/FeIr-NC catalyst achieves a record-low bifunctional gap (ΔE = 0.57 V) and demonstrates superior performance in a flexible fiber zinc-air battery, offering a viable route toward high-performance power sources for wearable electronics.
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Jing Zhou, Yumin Chen, Wei Mao, Long Jiang, Huangjian Chen, Yunzhan Ying, Yulong Wan, Shifan Zheng, Ju Lin, Shikun Liang, Yuyuan Yao, Bingjie Wang, Ye Zhang, Lihua Gan, Huisheng Peng, Lie Wang (2026). Spatially Decoupled Single/Dual-Atomic Sites with Independent Bifunctional Activity for High-Performance Fiber Zinc-Air Batteries. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3805-1
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Frequently Asked Questions
What is the specific mechanism by which spatial decoupling of Fe single atoms and Fe–Ir dual-atom pairs overcomes the ORR/OER activity trade-off?
The spatial decoupling assigns ORR to Fe single atoms and OER to Fe–Ir dual-atom pairs, allowing independent optimization of each active site. This avoids the scaling relationship that forces a compromise when a single site must catalyze both reactions. The Fe–Ir pairs exhibit tunable spacing that modulates the electronic structure, enhancing OER kinetics, while Fe single atoms maintain high ORR activity, resulting in a bifunctional gap of 0.57 V.
How does the Fe/FeIr-NC catalyst's performance in a fiber zinc-air battery compare to commercial Pt/C + IrO2 in terms of power density and cycle life?
The Fe/FeIr-NC-based battery achieves a peak power density of 3920 W kg−1, which is a 1.4-fold increase in energy efficiency and a 2.6-fold extension in cycle life compared to the commercial Pt/C + IrO2 benchmark. These metrics demonstrate superior performance and durability, making it suitable for practical wearable applications.
What are the key structural features of the Fe/FeIr-NC catalyst that contribute to its high bifunctional activity?
The catalyst features isolated Fe single atoms and Fe–Ir dual-atom pairs dispersed on a nitrogen-doped carbon matrix. The Fe single atoms provide active sites for ORR, while the Fe–Ir pairs, with tunable spacing, are optimized for OER. This architecture ensures high atomic utilization and allows independent tuning of each site's electronic environment, leading to the record-low ΔE of 0.57 V.
What is the significance of the bifunctional gap (ΔE) of 0.57 V in the context of existing single- and dual-atom catalysts?
A lower ΔE indicates better overall bifunctional activity, as it represents the potential difference between the ORR half-wave potential and the OER overpotential. The achieved ΔE of 0.57 V is the lowest reported for single- and dual-atom catalysts, signifying that the Fe/FeIr-NC catalyst outperforms all previously reported catalysts in balancing ORR and OER activities, which is critical for efficient zinc-air batteries.
What are the potential scalability and cost implications of the spatial decoupling strategy for industrial production of bifunctional catalysts?
The synthesis of Fe/FeIr-NC involves dispersing metal atoms on a nitrogen-doped carbon matrix, which can be achieved using scalable methods such as pyrolysis of metal precursors and nitrogen-rich carbon sources. The use of Fe and Ir, though Ir is a noble metal, is minimized due to atomic dispersion, potentially reducing cost. The strategy is versatile and could be extended to other metal combinations, offering a pathway for cost-effective production of high-performance bifunctional catalysts for energy devices.
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