Effects of an easy-to-implement water management strategy on performance and degradation of polymer electrolyte fuel cells.

Intermittent switching between wet and dry reactant gases during operation in a polymer electrolyte fuel cell (PEFC) can improve performance stability, alleviating the effects of flooding by controlling the water content within the system. However, lifetime durability may be affected due to membrane electrode assembly (MEA) boundary delamination and membrane damage. Two relative humidity (RH) control strategies were investigated, using electrochemical performance and MEA degradation as critical indicators. It was found that intermittent switching between wet and dry gases does not accelerate fuel cell degradation if the duration of the dry gas period is set reasonably (dry gases stops before the voltage reaches the apex of the hump). Additionally, current and temperature distribution mapping was utilised to capture the dynamic response between these transitional stages. The switching of dry gases first makes the current density distribution homogeneous, and the maximum current density is reduced subsequently. Then, the current density near the inlet keeps decreasing. Intermittent switching between wet and dry reactant gases is easy to implement and overcomes limitations in mass transfer at medium and high current densities. • Long-term performance for intermittent RH control is compared to constant RH control. • TEM, XPS and SEM characterise Post-mortem MEAs to quantify the degradation. • Local dynamic response during gas switching is captured by current density mapping. [ABSTRACT FROM AUTHOR]