Rapid synchronous state-of-health diagnosis of membrane electrode assemblies in fuel cell stacks.

• Originally establish excitation-discharge-combined electrochemical model for MEA. • Propose excitation-discharge-combined SOH analytical method with single excitation. • Accurately identify and compare MEA parameters between cathode and anode tests. • Validate precision and stability of MEA inconsistency diagnosis at stake level. • Verify irreversibility of partial reactions in high-potential region of excitation. Consistency evaluation and degradation diagnosis of membrane electrode assemblies (MEAs) in fuel cell stacks are critical issues for fuel cell lifetime extension and commercialization. This study aims to develop a high-efficiency, high-precision, and synchronous state-of-health (SOH) diagnosis methodology for MEAs at the stack level. The micro-current excitation (MCE) method based on multiple excitations is used to evaluate the MEA inconsistency of a 22-cell commercial stack, involving hydrogen crossover, short-circuit resistance, electrochemical surface area, and double-layer capacitance. High precision is demonstrated by the consistency in the membrane-related parameters and the difference in the electrode-related parameters between the cathode and anode tests. Herein, an efficient single excitation and natural discharging (SEND) analytical method based on the excitation-discharging-combined equivalent circuit model is originally proposed. The accuracy of SEND can be demonstrated by comparing its results with the standard results of the MCE, which fit the baseline y = x with high linearity and identical evaluation of inconsistency. Moreover, the stability of the SEND is proved by its independence from the excitation current, which is reflected by the presence of tiny standard deviations. In addition, the bifurcation feature in the integrated net charge curves of the excitation and natural discharging processes proves the irreversibility of partial oxidation reactions in the high-potential region of excitation. The SEND significantly increases the testing efficiency using only a single excitation. It has promising prospects for the rapid consistency-based MEA screening, degradation evaluation, and recombination of MEAs. [ABSTRACT FROM AUTHOR]