Comprehensive experimental analysis of performance parameters and inductive process to determinate dynamic voltage characteristics for proton exchange membrane fuel cell

Abstract

Determining the dynamic characteristics is crucial for enhancing the efficiency and reliability of proton exchange membrane fuel cells (PEMFCs) system in hydrogen vehicle application. However, existing research lacks a comprehensive analysis of internal polarization processes and performance parameters, with an overemphasis on external voltage output signals. To address this gap, firstly, a practical polarization curve model integrated with dynamics of platinum oxidation and gas diffusion is established to obtain performance parameters. This model, in contrast to the traditional Butler-Volmer equation, can reproduce the doubling of Tafel slope. Then, this study introduces, for the first time, the ultra-low frequency inductive impedance of electrochemical impedance spectroscopy (EIS) to reveal the internal mechanism of dynamic response. After analyzing the relationship between dynamic voltage and impedance characteristics, an extended distribution of relaxation times (DRT) method is introduced, alongside an improved distributed transmission line model (TLM), enabling the quantitative analysis of inductive processes. Finally, the study evaluates the impact of operating conditions and degradation on dynamic characteristics from the perspectives of voltage signals, polarization decomposition, performance parameters, inductive process resistance, and current distribution heterogeneity, revealing the underlying mechanisms. The results indicate that dynamic responses primarily depend on the transient resistances associated with platinum oxidation and oxygen diffusion, which affect the transition in activation and concentration overpotentials. Additionally, diffusion resistance is related to oxide coverage. The internal humidity is a key factor as higher water activity facilitates intermediate reactions involving platinum. This study provides valuable insight into PEMFCs dynamic performance and guidance for system control optimization.