Surface Fluorination to Boost the Stability of the Fe/N/C Cathode in Proton Exchange Membrane Fuel Cells

The ternary Fe/N/C material is a promising non‐precious‐metal oxygen reduction electrocatalyst for proton exchange membrane cells (PEMFCs). However, its practical application is severely hampered by poor stability under PEMFC working conditions, especially at a cell voltage higher than 0.5 V. Herein, we report a new strategy to significantly improve the stability of the Fe/N/C catalyst in PEMFCs by covalent grafting of a trifluoromethylphenyl (Ar‐CF 3 ) group. The hydrophobic character of Ar‐CF 3 can effectively prevent water flooding of the Fe/N/C catalyst layer, and thus form robust mass‐transport channels for gas−liquid two‐phase flow. Simultaneously, both electron‐withdrawing and hydrophobic properties considerably suppress the oxidative corrosion of the carbon matrix that hosts the catalytically active sites. Therefore, fluorinated Fe/N/C could perform stably over 100 h at 0.5 V with a current density of 0.56 A cm −2 in a H 2 −O 2 PEMFC. Even when the cell voltage increased to 0.6 V, only 15 % performance was lost after 100 h operation.