The ionomer binder is crucial for the preparation of homogeneous catalyst layers for anion exchange membrane fuel cells (AEMFCs). However, the dense stacking of the ionomer on the catalyst surface results in large resistance to gas (especially O₂) penetration in the three-phase boundary (TPB). Here, an in situ UV-driven gas “expressway” for the catalyst layer of AEMFCs was prepared by a rigid anthracene-based cross-linkable ionomer. The gas permeability of the catalyst layer was increased by 130% after crosslinking due to the high free volume between the ionomer chain segments. Meanwhile, the electrochemical and identical location transmission electron microscopy (IL-TEM) characterizations showed that the crosslinked ionomer binders played an anchoring role for the catalyst particles. The performance of an H₂/O₂ AEMFC (based on commercialized FAA-3-50 membranes) containing the crosslinked ionomer is much better than that of the uncrosslinked PPOAN ionomer. The in situ UV-driven crosslinking strategy of catalyst layers provides new insights into the preparation of homogeneous mesoscopic structures for the catalyst particles. More importantly, the rigid anthracene-based crosslinked structure constructs microscopic gas channels in the ionomer–catalyst interface, which has been overlooked in previous work.