Quantifying degradation in hydrogen fuel cells: A holistic approach combining in situ and ex situ characterizations

The effective utilization of green hydrogen to buffer the intermittency of renewable energy sources is currently limited by the durability, efficiency, and reliability of hydrogen fuel cells. Overcoming these barriers is essential for the economic viability of renewable energy systems, requiring both material enhancements and optimized operation via energy management strategies (EMSs). An in-depth understanding of degradation in operando and in situ plays a key role in developing robust EMSs capable of extending the lifespan of hydrogen power systems. Existing studies relying on voltage are limited in providing insights into individual physicochemical processes. This work investigates the degradation quantification of fuel cells using in situ electrochemical impedance spectroscopy. Using a distribution of relaxation times–based methods, the frequency-domain impedance data can be transferred into the time domain to decompose the physicochemical processes of fuel cells. The degradation causes are identified by quantifying the contribution percentage of those processes to the overall voltage decay. This approach is validated using a dynamic driving load profile-based durability dataset. The results show that the charge transfer process is the dominant factor for overall degradation, accounting for 55 % of the overall voltage losses at 1.0 A cm−2. This study provides useful insights into degradation diagnostics, facilitating the development of more durable hydrogen converters for the global transition to renewable energy.