Simultaneous incorporation of tungsten oxide (WO _x ) and cerium (Ce) ions into proton exchange membranes (PEMs) enhances their chemical durability while imposing minimal penalties on fuel cell performance. WO _x decomposes hydrogen peroxide, while Ce ions scavenge hydroxyl radicals. Their complementary functions, combined with the immobility of WOx, enable effective and performance-conscious suppression of membrane degradation.

To improve the chemical durability of proton exchange membrane fuel cells (PEMFCs) while imposing minimal performance penalties, the effects of simultaneously incorporating tungsten oxide (WO _x ) and cerium (Ce) ions into the membrane are evaluated. Open-circuit voltage (OCV) hold tests are conducted using Nafion membranes containing Ce ions alone, WO _x alone, or both. The combination of Ce³⁺, a hydroxyl radical scavenger, and WO _x , a hydrogen peroxide decomposition catalyst with high stability and immobility under acidic conditions, achieves a degradation suppression effect that is consistent with the product of their individual contributions. The distinct mitigation mechanisms of Ce ions and WO _x are supported by ex situ H₂O₂ decomposition experiments and membrane molecular weight analysis. No marked initial performance loss is observed with WO _x addition. These results indicate that the use of WO _x allows for reduced Ce ion loading and that it mitigates negative effects associated with Ce ion mobility. The combined use of suppressants that target different degradation pathways presents a promising strategy for achieving high membrane durability with minimal performance tradeoffs.