Several studies have been conducted to solve the challenges of commercializing PEMFCs. Thermal management , water management , and oxygen transport resistance account for the majority of investigations. The operating conditions of PEMFC , its flow field , and the optimization of properties of cells have all been investigated. Modified catalysts , the properties of the Gas Diffusion Layer (GDL) , the clamping pressure of cells , degradation , hydrogen economy were also studied. The investigations unveiled the behaviour of PEMFC at different conditions.