Polymer electrolyte membrane fuel cells (PEMFCs) have faced challenges in achieving their lifespan goals due to the degradation

of the membrane electrode assembly (MEA) during long-term operation. To enhance the durability of PEMFCs,

it is necessary to research materials that can improve the durability of the membrane and electrodes, as well as to study

operating conditions that can reduce degradation. This paper investigated methods to mitigate the membrane degradation

of electrochemically degraded MEAs by controlling humidity and temperature among the operating conditions. MEA was

degraded electrochemically by conducting open circuit voltage (OCV) holding, and then the degradation rate according

to temperature and humidity changes was observed through fl uoride emission rate (FER) change. In a degraded MEA, it

is shown that increasing cell humidity accelerates membrane degradation. According to linear sweep voltammetry (LSV)

results, this was confi rmed to be due to the increase in hydrogen permeability caused by the higher humidity. The decrease

in temperature lowered the rate of membrane degradation, which is attributed to a decrease in the rate of radical attack and

generation resulting from the temperature decrease. Therefore, it was confi rmed that to mitigate membrane degradation in

electrochemically degraded MEAs, it is eff ective to reduce temperature and humidity, thereby decreasing the rate of radical

formation.