Direct hybridization of PEMFC and supercapacitors: Effect of excess hydrogen on a single cell fuel cell durability and its feasibility on fuel cell stack

The present paper focuses on the effect of reduced hydrogen stoichiometry on the dynamic behavior of a PEMFC directly hybridized with SC or non-hybridized, using the European standard cycling protocol (FC-DLC) for transport applications. Two gas stoichiometry factors have been considered, at 1.2 and 1.1. Whereas direct hybridization of a single cell enables to reduce the hydrogen overconsumption from 28% to 20% at hydrogen stoichiometry of 1.2, the overconsumption was further reduced to 10% by reducing the stoichiometry to 1.1. The durability of a single fuel cell has been investigated by comparing the long-term cycling operation depending on the hydrogen stoichiometric conditions, for both hybridized and non-hybridized fuel cell. The non-hybridized fuel cell, at hydrogen stoichiometry of 1.2, was operated for 687 h (end of life), whereas the non-hybridized fuel cell at 1.1, could not be operated due to the sudden, excessive voltage drop in the high current density period of the cycle. On the contrary, the hybridized fuel cell was successfully submitted to cycling for more than 1000 h at both conditions of hydrogen stoichiometry. The GDL appears to be responsible for the failure of non-hybridized fuel cell performance, whereas no particular degradation was evidenced with hybridized configurations. Finally, the technique has been successfully applied to a three-cell stack, with very comparable voltage profiles of the individual cells over the cycling protocol. [Display omitted] •Hybrid vehicles consisting direct hybridization of fuel cell and supercapacitors are convincing.•Direct hybridization allows to operate even at lower hydrogen supply.•Low hydrogen supply is only sustainable in direct hybridization mode.•Lower hydrogen supply in direct hybridization mode does not impact the durability.•Direct hybridization is also feasible for fuel cell stack.