Heat generation of fuel starved cells in PEMFC stacks, comparing carbon and metal bipolar plates

Poster presentation A1809 at conference European Fuel Cell Forum, Lucerne, Switzerland at 1 - 4th July 2025

Abstract

Fuel gross starvation is an irregular operation state, which occurs when fuel cells are operated in multi-cell stacks with insufficient supply of hydrogen. The cell voltage polarity is reversed to negative values in this case, so the fuel cell acts like an electrical resistance. 
Two characteristic experiments of fuel starvation are compared. Each experiment intentionally provoked the error state of fuel starvation of a single cell in a 20-cell stack. One scenario used a metal containing bipolar plate (BP), and the experiment ended quickly in a rapid decrease of cell voltage to -10 V, causing catastrophic cell failure. The other experiment used carbon composite BPs, whereas no such destructive behavior could be observed.
The observed high relevance of BP material is explained for such error states of fuel starvation in multi-cell stacks. The exact local behavior of the fuel starved cell is compared for both BP materials in form of spatially distributed current density, temperature and cell voltage measurements. 
This data shows that the rapid voltage decrease of the fuel starved cell was caused by intense overheating. This extreme overheating was effectively mitigated when carbon BPs were used. The local cell voltage then varied between inlet and outlet due to electric cell-to-cell interaction phenomena in the multi-cell stack. As a consequence, the local cell voltage maintained positive at the H₂ rich inlet region, counteracting the heat production.