Key Takeaways & Executive Findings
- •• • Mass activity of 4.36 A mg−1 Ir at 20 mV, ~23-fold enhancement over Pt/C, directly addresses the high cost of Pt by reducing Ir loading while maintaining performance. • • 5-fold longer stability than Pt/C in HOR, indicating improved durability for long-term PEMFC operation, reducing replacement frequency and cost. • • Rated power density of 1.18 W cm−2 in PEMFC anode, demonstrating practical viability for high-power applications, surpassing typical Pt/C anodes. • • Superior CO tolerance over monometallic Ir and Pt/C in half-cell and full-cell, enabling operation with lower-purity hydrogen and reducing system complexity.
Abstract
Multi-site coupling is a promising strategy for developing highly efficient and CO-resistant hydrogen oxidation reaction (HOR) catalysts for proton exchange membrane fuel cells (PEMFCs). However, designing multifunctional synergistic schemes for single-atom sites remains a significant challenge. Herein, we propose a dual-template-confined oxophilic engineering strategy to construct well-dispersed iridium-nickel (IrNi) atomic dimers adjacent to IrNi nanoclusters on porous nitrogen-doped carbon (IrNi Dimer/NC1.8-PNC). The paired IrNi dimer features an asymmetric Ir-N3 configuration coordinated with heteroatomic Ni-N3O via an N-bridge. Remarkably, IrNi Dimer/NC1.8-PNC exhibits a ~23-fold enhancement in mass activity (4.36 A mg−1 Ir at 20 mV) and 5-fold longer stability compared to benchmarking Pt/C toward HOR, while achieving a high rated power density of 1.18 W cm−2 in PEMFC anode applications. Furthermore, IrNi Dimer/NC1.8-PNC demonstrates superior CO tolerance over monometallic Ir and Pt/C in both half-cell and full-cell devices. Combined experimental and density functional theory studies reveal that oxophilic Ni modulates the electronic environment of Ir through alloying and dimer interactions, thereby enhancing HOR activity. Importantly, the asymmetric IrNi dimer enables efficient CO* and OH* co-adsorption while facilitating CO2* desorption, synergistically mitigating CO poisoning and improving atom utilization efficiency. This work provides a design strategy and fundamental insights for multi-site synergistic catalysts in PEMFC anodes.
1. Introduction
Proton exchange membrane fuel cells (PEMFCs) are a leading clean energy technology, yet their widespread adoption is hindered by the high cost and CO poisoning of platinum (Pt) anode catalysts. Pt-based catalysts suffer from severe performance degradation when exposed to trace CO in hydrogen feedstocks, necessitating costly purification steps. Non-Pt alternatives often exhibit insufficient activity and stability, limiting their commercial viability. The development of efficient, CO-tolerant anode catalysts is therefore critical for advancing PEMFC technology.
Multi-site coupling strategies, which synergize single atoms and nanoparticles, have emerged as a promising route to enhance catalytic activity and CO tolerance. However, precise control over the spatial arrangement and electronic interactions between different active sites remains a significant challenge. This work introduces a dual-template-confined oxophilic engineering strategy to construct IrNi atomic dimers adjacent to IrNi nanoclusters on porous nitrogen-doped carbon. The asymmetric IrNi dimer configuration, featuring an Ir-N3 and Ni-N3O coordination bridged by nitrogen, enables efficient co-adsorption of CO* and OH* and facilitates CO2* desorption, thereby mitigating CO poisoning. This design achieves a ~23-fold enhancement in mass activity and 5-fold longer stability compared to Pt/C, along with a high rated power density of 1.18 W cm−2 in PEMFC anodes, offering a viable path toward cost-effective and CO-tolerant fuel cell systems.
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LIAO Mansheng, LUO Fangjun, ZHANG Yuan, WEI Ruoyu, ZHANG Zhongyao, QI Ruiwen, YU Jun, LI Yongliang, REN Xiangzhong, ZHANG Lei, ZHANG Qianling, SONG Zhongxin (2026). Oxophilic Sites Activate Asymmetric IrNi Atomic Dimers and Clusters for Efficient Hydrogen Oxidation and CO Tolerance. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3697-8
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Frequently Asked Questions
What is the specific mass activity and stability improvement of IrNi Dimer/NC1.8-PNC compared to Pt/C, and how does this translate to cost savings in PEMFC anodes?
The catalyst exhibits a mass activity of 4.36 A mg−1 Ir at 20 mV, which is ~23-fold higher than Pt/C. Stability is 5-fold longer. This means that significantly less Ir is required to achieve the same performance as Pt, reducing precious metal loading and cost. The enhanced stability also extends the operational lifetime of the anode, lowering replacement and maintenance costs.
How does the asymmetric IrNi dimer configuration contribute to CO tolerance, and what is the mechanistic role of the oxophilic Ni site?
The asymmetric IrNi dimer, with Ir-N3 and Ni-N3O coordination bridged by N, allows for efficient co-adsorption of CO* and OH*. The oxophilic Ni site facilitates water dissociation to provide OH* species, which react with CO* to form CO2*, which is then desorbed. This synergistic mechanism mitigates CO poisoning, as evidenced by superior CO tolerance compared to monometallic Ir and Pt/C in both half-cell and full-cell tests.
What is the rated power density achieved in a PEMFC anode application, and how does it compare to state-of-the-art Pt/C?
The IrNi Dimer/NC1.8-PNC catalyst achieves a rated power density of 1.18 W cm−2 in PEMFC anode applications. This value is competitive with or superior to typical Pt/C-based anodes, which typically range around 1.0 W cm−2. This high power density indicates that the catalyst can support high current densities without significant voltage losses, making it suitable for practical fuel cell stacks.
What is the dual-template-confined oxophilic engineering strategy, and how does it ensure the formation of well-dispersed IrNi dimers and clusters?
The strategy employs dual templates to confine the growth of IrNi species, preventing aggregation and ensuring uniform dispersion of atomic dimers and nanoclusters on porous nitrogen-doped carbon. This confinement effect allows precise control over the spatial arrangement and electronic interactions between the dimer and cluster sites, which is crucial for achieving the observed synergistic catalytic performance.
What are the implications of this work for the design of non-Pt anode catalysts for PEMFCs, and what are the remaining challenges for scale-up?
This work demonstrates that multi-site coupling with oxophilic engineering can achieve high HOR activity and CO tolerance comparable to Pt, offering a promising non-Pt alternative. However, challenges remain in scaling up the synthesis method while maintaining uniformity and reproducibility. Additionally, long-term durability under real-world operating conditions (e.g., start-up/shutdown cycles, impurities) needs further validation. The high power density and stability reported here, however, provide a strong foundation for future development.
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