Under the condition of dynamic load

Under the condition of dynamic load, thermal/humidity cycling, gas starvation, and potential cycling create the most adverse working environment for the MEA, as described in section 4.1. Consequently, mechanical degradation of components, carbon corrosion, and catalyst aging are radically accelerated. Fault conditions, including water flooding and membrane dehydration, may occur during a load changing process [16,34], and cause a rapid decay in performance. These performance decays can be recovered with proper management, so they are reversible and avoidable. It must be noted that this section focuses on the irreversible degradation.4.2.1. Multi-aspects of mechanical degradation Mechanical degradation of components results from fluctuations in water state under the condition of dynamic load. The electrode reaction and electro-osmotic drag are both enhanced at greater loads, which leads to water absorption and elevated water content in the membrane and ionomer. Conversely, the membrane and ionomer will dehydrate, and the water content decreases. The proton conductivity of the membrane is closely related to its water content [210], as shown in the formula [211,212]: