Key Takeaways & Executive Findings
- •• • CO electrooxidation onset potential of ~0.13 V vs. RHE, determined by two independent methods (background-corrected current >0 mA cm-2 in COOR tests and forward scan current exceeding N2 background in CO-stripping), enabling low-potential CO removal that reduces anode overpotential and improves PEMFC efficiency under reformate operation. • • Maximum power density under 100 ppm CO exceeds that of reported advanced catalysts (Table S5), demonstrating superior CO tolerance and potential for direct integration with reformate hydrogen without complex purification, lowering system cost and complexity. • • Hydrophilic Cr single-atom sites weaken CO adsorption on Pt through electronic regulation while promoting water activation, addressing the fundamental bottleneck of Pt poisoning by trace CO that plagues conventional PEMFC anodes. • • The dual-function mechanism—electronic modulation and water activation—provides a design principle for anti-poisoning catalysts, potentially extending to other noble-metal systems and reducing reliance on high Pt loadings, with industrial implications for automotive and stationary fuel cell applications.
Abstract
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
1. Introduction
Proton exchange membrane fuel cells (PEMFCs) represent a leading zero-emission power technology for transportation and stationary applications, yet their widespread deployment is constrained by the extreme sensitivity of Pt anodes to trace carbon monoxide. Even 10 ppm CO in reformate hydrogen can poison Pt sites, shifting the CO electrooxidation onset potential to values that overlap with the operating potential of the anode, thereby causing severe voltage losses and irreversible performance degradation. Conventional mitigation strategies—such as increasing Pt loading, alloying with Ru, or employing high-temperature operation—either escalate cost, compromise durability, or introduce operational complexity, failing to deliver a commercially viable solution for low-temperature PEMFCs.
This study introduces a hydrophilic single-atom interface on Pt, designated Pt@CrSA-N-C, which fundamentally alters the CO electrooxidation pathway. The Cr single-atom sites serve a dual role: they electronically modify adjacent Pt atoms to weaken CO binding, and they facilitate water activation to supply oxygenated species at low potentials. This synergistic effect lowers the CO oxidation onset potential to approximately 0.13 V vs. RHE, as confirmed by two independent measurement protocols. The resulting catalyst achieves a maximum power density under 100 ppm CO that outperforms reported advanced catalysts, establishing a new benchmark for anode anti-poisoning. By resolving the trade-off between CO tolerance and Pt utilization, this interface engineering strategy offers a practical route to simplify fuel processing and reduce system costs in PEMFC deployment.
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WANG Kangcheng, WEI Kai, GAO Siming, YANG Tongtong, TANG Meijian, HOU Lina, GE Junjie (2026). Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4419-1
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Frequently Asked Questions
What is the precise onset potential for CO electrooxidation on Pt@CrSA-N-C, and how was it measured to ensure comparability with literature?
The onset potential is approximately 0.13 V vs. RHE, determined by two independent methods: (1) the potential at which the background-corrected current first exceeds 0 mA cm-2 during CO oxidation reaction tests in a standard three-electrode system, and (2) the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. This dual-method approach enhances transparency and allows direct comparison with reported values.
How does the maximum power density under 100 ppm CO compare to state-of-the-art catalysts, and what are the implications for practical PEMFC operation?
The maximum power density of Pt@CrSA-N-C under 100 ppm CO exceeds that of reported advanced catalysts, as compiled in Table S5. This superior performance indicates that the catalyst can maintain high power output even with CO-contaminated hydrogen, potentially eliminating the need for complex and costly CO purification steps in fuel processing, thereby reducing system cost and improving overall efficiency.
What is the mechanistic basis for the lowered CO oxidation potential, and how does the hydrophilic single-atom interface contribute?
The Cr single-atom sites on the hydrophilic interface weaken CO adsorption on adjacent Pt atoms through electronic regulation, while simultaneously promoting water activation to generate oxygenated species (e.g., OH*) at low potentials. This dual functionality facilitates the oxidative removal of CO at reduced overpotentials, as evidenced by structural, spectroscopic, and electrochemical characterizations.
What are the potential failure mechanisms or degradation pathways for Pt@CrSA-N-C under prolonged PEMFC operation with CO-containing fuel?
While the manuscript does not provide long-term durability data, the hydrophilic single-atom interface may be susceptible to Cr dissolution or agglomeration under acidic and potential-cycling conditions. Future studies should assess Cr leaching rates and Pt sintering to ensure operational stability over thousands of hours.
What are the scalability and cost challenges for synthesizing Pt@CrSA-N-C, and how do they compare to conventional PtRu catalysts?
The synthesis involves single-atom Cr sites on N-doped carbon, which may require precise control of metal loading and coordination environment. While Cr is earth-abundant and cheaper than Ru, the scalability of the atomic interface deposition and the long-term stability of the single-atom sites need validation. Cost parity with PtRu will depend on reducing Pt loading and simplifying manufacturing.
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