Open Access

This study presents post-mortem analyses of polymer electrolyte membrane fuel cell (PEMFC) stacks operated using previously published accelerated durability test (ADT) protocols. Each ADT, lasting 1,200 h, was derived from a 5,500 h automotive-relevant reference test and designed to isolate the effects of load cycling, operating temperature, and humidity cycling. All major membrane electrode assembly components, the membrane, catalyst layers, and gas diffusion layers (GDL), were characterized using SEM, EDX, IR thermography, contact angle measurements and XPS, and the results then correlated with prior in situ diagnostics. Elevated temperature and humidity cycling were identified as the most detrimental stressors under system-relevant operating conditions that included voltage clipping at 850 mV. These conditions led to accelerated carbon corrosion, increased platinum dissolution and cobalt leaching in the cathode catalyst layer, as well as a significant loss of hydrophobicity in the GDL. The membrane remained structurally stable, although localized stress indicators were observed. The results confirm that the applied ADT protocols successfully reproduce realistic degradation patterns and enable a differentiated assessment of stressor-specific aging phenomena. This provides a robust basis for refining accelerated stack testing methodologies and optimizing operating conditions for improved PEMFC stack durability.

This study presents a rule-based energy management system (EMS) for a light-duty transporter with a fuel cell-dominated powertrain. In such architectures, the smallcapacity battery cannot consistently provide the power and energy buffer required by optimal control strategies to maintain the fuel cell system (FCS) within its high-efficiency operating range, and it frequently exceeds its continuous power capability. Unlike conventional EMS designs, the proposed EMS incorporates battery charging and discharging power limits across multiple time scales, including long-term, short-term, and burst levels, into the control design to dynamically manage the power distribution between the FCS and the battery. A regenerative braking power control strategy is also introduced to balance the regenerative and FCS power during deceleration. Validation on a powertrain test bench with vehicle-identical components demonstrates that the proposed EMS effectively reduces FCS power fluctuations while keeping battery stress within predefined limits. An average FCS efficiency of 52.2% is achieved under the US06 drive cycle. The efficiency and robustness of the EMS are confirmed by real measurement results, highlighting its readiness for practical implementation.

Durability of proton exchange membrane fuel cells (PEMFCs) in single-cell setup is often assessed using potentiostatic test protocols under inert cathode atmosphere, such as the US DOE’s accelerated stress tests (ASTs). Although these voltage-controlled protocols impose consistent electrochemical stress, they do not accurately replicate real-world operating conditions, for instance due to the lack of product water formation in the cathode or due to the generation of heat. In contrast, stress testing under hydrogen and air, which is commonly employed for PEMFC durability testing on stack level, reflect the hybrid potential- and current-controlled degradation modes which are typical of mobile applications. This is usually done galvanostatic, but can also be realized in a voltage controlled manner. There are notable differences in the ageing behaviors between those two methods: Potentiostatic testing protocols, in which the voltage remains constant throughout the test duration, induce consistent electrochemical stress regarding potential driven degradation modes such as platinum dissolution, Ostwald ripening, carbon corrosion and chemical membrane degradation due to hydrogen peroxide formation. In contrast, galvanostatic testing protocols result in a gradual decline in potential with time, thereby reducing potentially driven electrochemical stress. However, in galvanostatic mode, water production remains constant (unlike in potentiostatic mode), which is known to contribute equally to fuel cell degradation. This dynamic of varying potential driven and humidity driven stress significantly affects catalyst and membrane durability, underscoring the need to understand the degradation behavior specific to each testing method. The present study compares the impact of load-cycle and voltage-cycle protocols on PEMFC degradation. Electrochemical characterizations, such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), are used to identify the ageing behavior of the individual components. All tests were performed using commercial Gore® PRIMEA® membrane electrode assemblies (MEA) in a Baltic quickConnect high amp test cell with an active area of 12 cm². Our findings highlight the importance of testing under hydrogen and air to better replicate operational conditions and enhance PEMFC durability in practical applications.

This study presents a proof of concept for the integration of open circuit reference electrodes (OC-REs) in proton-exchange membrane water electrolysis (PEMWE) cells to understand electrode performance and loss mechanisms, allowing for unequivocal assignment of these losses to anode and cathode. OC-REs, which are non-invasive to cell performance and share the same environment as the working electrodes (WEs), are assessed for stability and reproducibility while their performance is investigated across varying current densities and membrane thicknesses. Results demonstrate the significant impact of hydrogen crossover on the potential of the anode RE, impact that was modeled by calculating a current-density-dependent mixed potential. When comparing half-cell and full-cell polarization, the latter shows significantly higher reproducibility, with proper electrode alignment being crucial to minimize differences in half-cell polarization curves. Conversely, no significant impact from alignment on half-cell electrochemical impedance spectroscopy (EIS) was observed, making this technique the more consistent approach. The half-cell EIS revealed a significant contribution from the cathode to the overall loss, contrary to indications from most studies lacking this half-cell insight. These findings illustrate the potential of OC-REs as effective sensors for assessing electrode contributions, paving the way for future investigations into optimizing PEMWE.

Ein Ziel im Projekt "cleanEngine" war es, eine hoch innovative Entwicklungsplattform zur dynamisch-energetischen Optimierung von Brennstoffzellenantrieben für leichte Nutzfahrzeuge zu schaffen. Die Fokusse lagen in der Erhöhung der Reichweite, der Steigerung der Energieeffizienz und Untersuchungen zur Skalierbarkeit. Dabei standen die Anpassungsfähigkeit an verschiedene Betriebsbedingungen, einschließlich dynamischer Lastzyklen und Temperaturschwankungen, im Mittelpunkt.