Volume 62

Unraveling the Spatial Heterogeneity in Activation Process of PEMFC under Air Starvation: Correlating In-situ Temperature Uniformity with Ex-situ Electrochemical Performance Qiwen Pan, Zhixun Xiong, Jida Men, Yuan Gao

Abstract

The air starvation protocol is a common method for rapid activation of proton exchange membrane fuel cells (PEMFCs) due to its efficiency. However, its impact on the spatial uniformity of the membrane electrode assembly (MEA) performance remains poorly understood, as conventional methods only assess overall performance. This study proposes a novel methodology that correlates in-situ temperature distribution during activation with ex-situ electrochemical performance mapping to unravel this critical issue. During the air starvation activation of a 300 cm² MEA, the temperature was monitored in real-time at 11 strategic locations on the bipolar plates. Carefully divide the MEA into 3 samples of 5 cm² each, which are distributed along the direction of oxygen flow. Each segment underwent comprehensive electrochemical characterization including cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS).
The results revealed significant spatial heterogeneity. In-situ temperature monitoring identified pronounced thermal gradients: a maximum difference of 1.6°C within a single bipolar plate and 4.7°C across the 5-cell stack, consistently showing higher temperatures near the oxygen outlet Ex-situ analysis confirmed substantial performance inconsistency across the MEA. The electrochemical active specific surface area (ECSA) derived from CV varied by up to 61.9% between regions—peaking at the oxygen outlet (15.73 m²/g) and bottoming at the center (5.99 m²/g)—consistent with the local temperature fluctuations during activation.
Critically, an association was observed between the local temperature profiles during activation and the final electrochemical parameters. Areas with higher activation temperatures tended to exhibit different ECSA and mass transport properties, suggesting localized variations in the activation efficacy. This work provides valuable insights into the heterogeneous nature of the air starvation process and demonstrates how such inhomogeneity can lead to spatial performance inconsistencies in the MEA. Our findings suggest that future activation protocols could be improved by considering spatial uniformity to enhance overall MEA quality.

Keywords PEMFC activation, air starvation, spatial heterogeneity, in-situ temperature, electrochemical impedance spectroscopy