Study of the impact of reactants utilization on the performance of PEMFC commercial stacks by impedance spectroscopy

Reactants utilization is a key stake for a PEMFC system: a too low utilization leads to a waste of reactant but a too high utilization may result in a detrimental starvation. To study these impacts, two commercial stacks were characterised by impedance spectroscopy under different hydrogen and oxygen utilizations (from nominal conditions to quasi-starvation). One was fresh while the other was operated on-field during 10,000 h. This study shows that the two capacitive loops in the lowest frequency range (1 Hz and below) correspond respectively to oxygen and hydrogen mass transfer limitations: the limiting reactant can be clearly identified from the impacted frequencies. The size of these loops was increased by up to 30% when the cell operated at high reactant utilizations. These results could therefore pave the way to the development of algorithms able to estimate the degree of starvation of some cells. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Reactants utilization is crucial for a PEMFC system, with too low or too high utilization leading to negative consequences. Impedance spectroscopy analysis revealed that the size of capacitive loops can indicate reactant limitations, suggesting the potential development of algorithms to estimate cell starvation levels.