Mechanistic Insights Into Cathode Degradation During Startup‐Shutdown of PEM Water Electrolysis and Mitigation via Semi‐Embedded Pt/CeOx

Why It Matters

Improved cathode durability lowers operating costs and helps meet DOE 2026 PGM loading targets, accelerating green hydrogen deployment.

Key Takeaways

• Startup‑shutdown spikes cathode potential to ~1.0 V.
• Pt/C suffers carbon corrosion and Pt particle agglomeration.
• Semi‑embedded Pt/CeOx provides strong metal‑support interaction.
• Catalyst achieves 8.3 µV h⁻¹ degradation at 0.05 mg Pt cm⁻².
• Durability exceeds DOE 2026 PGM loading goals.

Pulse Analysis

Proton exchange membrane water electrolysis (PEMWE) is emerging as a cornerstone for large‑scale green hydrogen production because it can operate at high current densities and respond quickly to renewable electricity fluctuations. Yet, the often‑overlooked startup‑shutdown phase imposes a sudden rise in cathode potential to around 1.0 V versus RHE, exposing the catalyst to oxidative stress. This transient condition accelerates degradation pathways that are negligible during steady‑state operation, creating a hidden cost factor for electrolyzer owners and system integrators.

The research team reproduced realistic cycling in a three‑electrode cell and monitored the cathode voltage trajectory. When hydrogen supply ceased, the lack of reduction current forced the electrode into an anodic regime, triggering carbon corrosion of the support and coalescence of platinum nanoparticles. Post‑mortem microscopy confirmed extensive Pt agglomeration and loss of surface area, while electrochemical impedance spectroscopy revealed increased charge‑transfer resistance. These observations pinpoint the primary degradation mechanisms that compromise hydrogen evolution efficiency during repeated start‑up and shut‑down events.

To break this cycle, the authors introduced a semi‑embedded Pt/CeOx catalyst in which platinum particles are partially anchored within a cerium‑oxide matrix. The strong metal‑support interaction stabilizes the Pt surface, curtails oxidation of the carbon scaffold, and limits particle growth. Tested at an ultralow loading of 0.05 mg Pt cm⁻², the new electrode delivered a hydrogen evolution overpotential of just 27 mV at 100 mA cm⁻² and a degradation rate of 8.3 µV h⁻¹ over 600 h—more than ten times lower than conventional Pt/C. This performance not only meets but surpasses the DOE 2026 target for precious‑metal loading, offering a viable path toward cost‑effective, long‑life PEM electrolyzers.