Performance‐Conscious Coadditive Approach for Enhancing Proton Exchange Membrane Durability: Roles of Tungsten Oxides and Cerium Ions

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 Ce 3+ , 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 H 2 O 2 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.