(Invited) Modeling of Catalyst Degradation in Toyota's Mirai and Its Application to Target-Setting for Future PEFC's Durability

Abstract

To popularize Polymer electrolyte fuel cells (PEFCs) as a power source for various types of mobility, improving their durability is necessary. One of the factors that determines the durability of PEFCs is the electrochemical surface area (ECSA) loss of the cathode catalyst which causes a drop in PEFC’s output power and generation efficiency. The loss of ECSA has been modeled by a mechanism based on Ostwald ripping, and the model has been validated by accelerated stress testing (AST) [1]. Using AST, it is possible to evaluate the durability of PEFCs with short time, but in actual applications, such as mobility, the inputs for PEFCs are complex rather than simple repetitive inputs, and the relationship with AST is not clear.In this study, we proposed a method for setting AST conditions that correspond to the stresses of actual applications. In order to correlate the AST with the real driving test, a simple model based on Ostwald ripping was developed, and the model was validated by experimental results for both actual vehicle tests and ASTs. Validation for the actual vehicle was performed between simulated values from Mirai's real driving data and post-driving measurements. Since the model represents well both the experimental results of both the AST and the actual vehicle, it is considered that the model can convert the stress intensity between the actual vehicle test and the AST.Using this model and PEFC vehicle model [2], we set a target durability required for future heavy-duty trucks, and the AST conditions to evaluate it. In the presentation, we will discuss the details of the proposed target-setting procedure and models.[1] R. Darling et al., J. Electrochem. Soc., 2003, 150, A1523[2] T. Watanabe, et.al, 242nd ECS Meeting, MA2022-02, 1468 (2022)