Durability improvement mechanism of proton exchange membrane fuel cell by microporous layer

Microporous layer (MPL) has been proven to significantly improve water management in proton exchange membrane fuel cells (PEMFC). However, its effects on fuel cell durability have not been fully revealed. In this contribution, the effects of MPL on the degradation of PEM fuel cells are investigated. Two single fuel cells, with and without MPL at the cathode, are assembled. The aging test is conducted and the cell performance is periodically characterized under various operating conditions. The experimental results show that the presence of MPL can effectively mitigate the degradation of PEMFC. The electrochemical impedance analysis at low current (150 mA cm(-2)) shows the fuel cell with MPL has a smaller increase in charge transfer resistance during aging test, indicating MPL can mitigate kinetic degradation. The scanning electron microscope (SEM) images show less thickness reduction in aged catalyst layer of the fuel cell with MPL, indicating MPL can protect the catalyst layer from carbon corrosion and micro-structure damage. Besides, the effect of MPL on mass transport loss is analysed, and the results show that MPL can alleviate the increase in mass transport loss during aging test. Under either wet (air relative humidity of 75% and 100%) or very low air flow rate conditions, the presence of MPL unambiguously improves the water transport for the fresh cell. Most importantly, the superior water management capability of MPL is sustained after the harsh aging test, reducing mass transfer resistance.