Electrolyzers are critical components in hydrogen production through water electrolysis, but they are susceptible to various failure modes that can degrade performance and reduce operational lifespan. Understanding these failure mechanisms and implementing mitigation strategies is essential for improving durability and efficiency. Accelerated aging tests help evaluate these failure modes under controlled conditions to predict long-term behavior.

One primary failure mode in electrolyzers is membrane degradation, particularly in proton exchange membrane (PEM) systems. The membrane, typically made of perfluorosulfonic acid (PFSA) materials like Nafion, undergoes chemical and mechanical degradation over time. Chemical degradation occurs due to reactive oxygen species (ROS) such as hydroxyl radicals formed during operation. These radicals attack the polymer structure, leading to loss of sulfonic acid groups and thinning of the membrane. Mechanical degradation results from cyclic stresses during startup-shutdown cycles or varying load conditions, causing pinhole formation or cracks. Mitigation strategies include using reinforced membranes with porous PTFE supports, incorporating radical scavengers like cerium oxide, and optimizing operating conditions to minimize radical formation.

Electrode corrosion is another significant failure mode, affecting both anode and cathode materials. In alkaline electrolyzers, nickel-based anodes can suffer from oxidation, leading to passivation or dissolution. In PEM electrolyzers, the oxygen evolution reaction (OER) at the anode accelerates corrosion of iridium or ruthenium oxide catalysts, reducing catalytic activity. Cathode materials, such as platinum, may also degrade due to particle agglomeration or dissolution under high overpotentials. Protective coatings, such as titanium or gold layers on porous transport layers (PTLs), improve corrosion resistance. Additionally, alloying catalyst materials (e.g., iridium with ruthenium) enhances stability while maintaining activity.

Catalyst layer delamination is a mechanical failure mode where the catalyst layer separates from the membrane or gas diffusion layer (GDL). This occurs due to interfacial stresses from thermal cycling or humidity variations. Delamination increases electrical resistance and reduces active sites for electrochemical reactions. Mitigation involves optimizing the electrode fabrication process, using adhesion promoters, and ensuring uniform compression in the cell stack.

Gas crossover is a critical safety and performance issue where hydrogen and oxygen permeate through the membrane, leading to mixed gas formation. This risk is higher in thin membranes or those with defects. Mixed gases can form explosive mixtures and degrade efficiency. Strategies to minimize crossover include using thicker membranes, incorporating barrier layers, and maintaining optimal pressure differentials between anode and cathode compartments.

Contaminants in feed water or process gases can poison catalysts or foul membranes. Cations like sodium or calcium ions displace protons in PEM membranes, reducing conductivity. Chlorides and sulfates can adsorb on catalyst surfaces, blocking active sites. Mitigation involves rigorous water purification, ion-exchange resins, and periodic membrane flushing. In alkaline systems, carbonate formation from CO2 absorption reduces electrolyte conductivity, requiring periodic electrolyte replacement or CO2 scrubbing.

Accelerated aging test methodologies are essential for evaluating these failure modes. Tests simulate years of operation within weeks by applying extreme conditions while monitoring performance degradation. Common protocols include:

1. Voltage Cycling: Repeated cycling between high and low potentials accelerates catalyst degradation and carbon corrosion.
2. Thermal Cycling: Alternating between high and low temperatures induces mechanical stresses in membranes and interfaces.
3. Humidity Cycling: Varying relative humidity levels test membrane swelling and shrinkage resistance.
4. Chemical Stress Tests: Exposing membranes to hydrogen peroxide solutions simulates ROS attack.
5. Load Cycling: Rapid changes in current density mimic real-world dynamic operation.

Performance metrics monitored during these tests include cell voltage, Faradaic efficiency, membrane conductivity, and gas crossover rates. Post-test analysis involves scanning electron microscopy (SEM) for morphological changes, X-ray diffraction (XRD) for catalyst crystallinity, and Fourier-transform infrared spectroscopy (FTIR) for chemical degradation.

Operational protocols also play a key role in mitigating degradation. Maintaining stable temperature and pressure reduces thermal and mechanical stresses. Avoiding low-load operation minimizes catalyst dissolution. Regular maintenance, such as membrane hydration management and impurity monitoring, extends component life.

In summary, electrolyzer failure modes stem from chemical, mechanical, and operational factors. Mitigation relies on material improvements, protective measures, and optimized protocols. Accelerated aging tests provide valuable data to predict lifespan and refine designs for greater reliability. By addressing these challenges, electrolyzers can achieve higher efficiency and longer service life, supporting sustainable hydrogen production.