Insight into catalyst layer ingredient distribution influence on reactive oxygen and heat transport in a PEMFC with LBM simulation

Effective reactive oxygen and heat transport within the catalyst layer (CL) modulated by ingredient distribution are essential for sustaining electrochemical performance in proton exchange membrane fuel cells (PEMFCs), yet the underlying microscopic mechanisms remain unclear. This work introduces a lattice Boltzmann model to simulate oxygen and heat transport in CLs with different ionomer and platinum distributions and to decouple the dominant factor governing reaction rate into reaction and transport terms. The results indicate that increasing the ionomer-to-electrode mass ratio expands the active reaction area, thereby enhancing the reaction rate while intensifying oxygen transport non-uniformity. Notably, an excessively high ionomer-to-electrode mass ratio markedly hinders oxygen transport, shifting the dominant factor governing the reaction rate from reaction limitation to transport limitation. Increasing the CL temperature enhances the reaction rate by up to 30% but also intensifies oxygen transport limitations, causing a relatively lower ionomer-to-electrode mass ratio to yield a higher reaction rate. A multilayer platinum distribution with a higher inlet platinum volume fraction that gradually decreases along the thickness direction redistributes the active reaction area across layers. This redistribution markedly reduces oxygen transport limited zones and improves platinum utilization, thereby further increasing the reaction rate by 5%. However, an excessively large interlayer difference aggravates platinum agglomeration and temperature non-uniformity, shifting the dominant factor governing the reaction rate from transport limitation to reaction limitation. These findings provide a mechanistic understanding of how CL ingredient distributions influence oxygen and heat transport and a decoupling analysis of their respective impacts on reaction performance in PEMFCs.