Proton-exchange membrane (PEM) dry–wet variation during PEM fuel cell (PEMFC) operation markedly affects PEMFC lifespan. Therefore, deeper insights into the mechanical degradation mechanism of PEM require analysis of the membrane dry–wet change process. The stress changes caused by PEM dry–wet variations may induce mechanical failure. In practice, although high-frequency resistance (HFR) is often used to indirectly characterize PEM dry–wet degrees, numerical simulation can effectively analyze the mass transfer inside a PEMFC for parameters that are difficult to measure directly experimentally (such as membrane water content). Additionally, three-dimensional (3D) model validation requires more comprehensive experimental methods. In this study, we validate the simulated resistance distribution results through local electrochemical impedance spectroscopy. We also discuss the mass- and heat-transfer distribution characteristics under different current densities and analyze the influence of these characteristics on local HFR distribution variations. The calculated HFR distribution results show a certain degree of agreement with the experimental results. Due to the membrane self-humidification effect, the position of the minimum HFR value shifts upstream of the cathode at a high current density. The observed change in membrane stress results from variations in membrane water and temperature distributions with changes in current density. Steady-state HFR distribution analysis to uncover the membrane dry–wet variations caused by load changes—which would affect the HFR distribution changes—reveal that the HFR at the air outlet and the membrane dry–wet variations are more pronounced than at other locations due to the influence of reaction rate and gas velocity. Overall, this study demonstrates that 3D simulations can reliably predict the local HFR distribution of PEMFCs, enabling membrane stress variation analysis and providing guidance for fuel cell design and operation.

The major challenges for the commercialization of proton exchange membrane fuel cells (PEMFCs) are durability and cost. Prognostics and health management technology enable appropriate decisions and maintenance measures by estimating the current state of health and predicting the degradation trend, which can help extend the life and reduce the maintenance costs of PEMFCs. This paper proposes an online model-based prognostics method to estimate the degradation trend and the remaining useful life of PEMFCs. A non-linear empirical degradation model is proposed based on an aging test, then three degradation state variables, including degradation degree, degradation speed and degradation acceleration, can be estimated online by the particle filter algorithm to predict the degradation trend and remaining useful life. Moreover, a new health indicator is proposed to replace the actual variable loading conditions with the simulated constant loading conditions. Test results using actual aging data show that the proposed method is suitable for online remaining useful life estimation under variable loading conditions. In addition, the proposed prognostics method, which considers the activation loss and the ohmic loss to be the main factors leading to the voltage degradation of PEMFCs, can predict the degradation trend and remaining useful life at variable degradation accelerations.