Computer modeling plays an important role in fuel cell design and performance optimization.A number of modeling studies have been conducted to better understand the impact of the water and thermal management on the performance of proton exchange membrane fuel cells (PEMFCs).This PEMFC modeling study assembles all components of a PEMFC into a unified domain for computation.In particular, this PEMFC model features: (1) allowing the thin catalysts to physically appear in the computational model instead of simply using them as interfaces; and (2) accounting for variable water content in the membrane instead of replying on the fully hydrated membrane assumption.