Analysis of local current density, temperature, and mechanical pressure distributions in an operating PEMFC under variable compression

This article investigates the impact of mechanical compression on local phenomena within an operating PEMFC with a large active area (225 cm 2 ). It explores the distributions of current density, temperature, and mechanical pressure, building on previous global characterisations (cell voltage, polarisation curves, and EIS). The study finds that mechanical compression (0.35–1.55 MPa) enhances the uniformity of current density and temperature distribution, reducing the risk of hotspots that can impair PEMFC performance and durability. The spatial analysis reveals that this homogenisation effect is mainly due to improved pressure distribution with increased compression. The regions with higher mechanical pressure correlate with higher local current density and temperature, which improves performance by reducing ohmic resistance. However, excessive compression at high current density and relative humidity can lead to water management issues. Overall, the results support the positive effect of pressure homogenisation on PEMFC performance, as observed in previous studies. • The effects of clamping on local phenomena in a 225 cm 2 PEMFC are studied. • Maps of load current, temperature, and mechanical stress are analysed. • The compression from 0.35 to 1.55 MPa homogenises the local currents/temperatures. • This homogenisation is linked to better stress distribution and ohmic loss decrease. • The enhancement of local distributions is correlated with higher cell voltages.