A scale-bridging model for proton exchange membrane fuel cells: Understanding interactions among multi-physics transports, electrochemical reactions and heterogeneous aging

The lifetime issues caused by catalyst degradation is one of the most critical challenges for the commercial application of proton exchange membrane fuel cells. However, the understanding concerning the interactions among transport, reaction, and catalyst degradation is inadequate for further durability enhancement. Herein, a scale-bridging model that couples a cell-scaled model to reveal the reactive transport process and a catalyst-scaled model to unveil Pt degradation is proposed to capture the degradation characteristics. It is found that the heterogeneous aging is observed in both the through-plane and channel-rib directions due to the enhanced mass loss near the membrane and the water accumulation under the rib, resulting in the mitigation of the core reaction region away from the membrane, thereby causing an increase in ohmic loss after cycles. More importantly, the local oxygen transport resistance increases with degradation, leading to a remarkable cell performance loss under high current density. Additionally, the influences of cell voltage load and inlet humidity on Pt degradation are also investigated. And the proposed gradient catalyst layer shows a significant mitigating effect on Pt degradation. This work reveals the degradation-performance interactions, which is conducive to design the high-performance fuel cell to prolong lifetime.