Proton exchange membrane (PEM) is critical for the efficient, reliable and safe operation of proton exchange membrane fuel cells (PEMFC). The lifetime of PEM is the main factor restricting the commercialization of PEMFC. The complexity of operating conditions, such as open-circuit/idling, dynamic load and startup-shutdown under automotive conditions, on PEMFC will cause the mechanical and chemical degradation of PEM and affect the service life of PEMFC. In order to understand the degradation behavior and durability of PEM, this paper presents an overview of the degradation failure mechanism and mitigation strategies of PEM. The mechanical and chemical degradation behavior of PEM and its causes, as well as the mitigation strategies are discussed in order to give a direction for PEM design and fuel cell system control strategy. It is proposed as a primary principle in order to further develop and promote the durability of PEM, to focus on the material improvement and system engineering.

The degradation of the catalyst layer is the main reason for the performance reduction of the proton exchange membrane fuel cells. The effects of high potential holding time, cell temperature, and relative humidity (RH) on carbon corrosion of cathode catalyst layer are studied in the present paper. The fuel cell was maintained at 1.4 V under three conditions (80°C and 100% RH, 60°C and 100% RH, 80°C and 40% RH) and at different durations. The carbon corrosion rate was faster under high temperature and high RH. After high-potential holding test, the membrane electrode assembly (MEA) showed a decrease in performance, electrochemical active surface area (ECSA), and proton conduction resistance within the catalyst layer, as well as an increase in charge transfer resistance. After maintaining 1.4 V for 180 min, the ECSA retention rate of MEAs are only about 30%. The changes in the ECSA and the proton conduction impedance precede the performance degradation, which could more quickly reflect the degradation of carbon materials. Furthermore, this work investigated the evolution process of carbon corrosion under high potential based on duration and proposed a three-stage degradation mechanism of the cathode catalyst layer.

Electrochemical reactions in proton exchange membrane fuel cells (PEMFCs) predominantly occur within the membrane electrode assembly (MEA), dictating power output and lifetime. As a key functional component of the catalyst layer (CL), ionomer plays a decisive role in establishing effective three-phase boundaries, maintaining proton-conducting networks. While the impact of ionomer-to-carbon (I/C) ratio on MEA performance has been recognized, its coupled effect on durability remains underexplored. Herein, MEAs with I/C ratios ranging from 0.4 to 1.2 were fabricated, and the influence of ionomer content on performance and durability was systematically investigated through microstructural characterization, electrochemical measurement, and accelerated stress testing. Results reveal distinct trade-offs: insufficient ionomer impairs proton transport and durability, while excess ionomer hinders mass transport and electrochemical performance but helps maintain CL stability. Specifically, an I/C ratio of 1.2 exhibits the highest durability but the lowest performance. An I/C ratio of 0.8 achieves the optimal peak power density (1156 mW cm^–2) while maintaining good durability, superior to lower I/C ratios. Balancing performance and durability, an I/C ratio of 0.8 emerges as the optimal choice. This work provides both experimental evidence and mechanistic insights into the influence of ionomer content in CL, offering guidance for the design of high-performance and durable PEMFCs.