Multi-indicator evaluation for determining the target water content state of low-temperature shutdown purge in proton exchange membrane fuel cells system

Purging to an appropriate water content state during shutdown at low temperature is essential for cold starts and fuel cell health. However, traditional single-indicator evaluations often overlook interactions between water content, cold start performance, and fuel cell lifetime, leading to suboptimal target water content determinations. Therefore, a multi-indicator evaluation for determining water content of low-temperature shutdown purge in proton exchange membrane fuel cell was conducted. Typical shutdown water content states were defined, and cold start experiments were performed to analyze the variations in cumulative water production and initial 1 kHz impedance under different conditions. Additionally, 85 freeze-thaw (F-T) cycles were carried out to quantify the effects of various shutdown water content on fuel cell lifetime through polarization resistance growth. Comprehensive evaluation identified State 3 as the optimal target water content state, achieving a balance among cold start capability, F-T cycles life, purging time, and initial 1 kHz impedance.