Rapid outgassing of hydrophilic TiO2 electrodes achieves long‑term stability of anion exchange membrane water electrolyzers

As global demand for green hydrogen surges, anion-exchange membrane water electrolyzers (AEMWEs) are gaining attention as a cost-effective alternative to proton-exchange membrane systems. However, electrode stability remains a critical bottleneck due to gas bubble accumulation that blocks active sites and accelerates catalyst degradation. Now, researchers from Kyungpook National University, led by Prof. Sang-Il Choi, have developed a super-hydrophilic electrode that achieves record operational stability by enabling rapid gas evacuation.

Why Super-Hydrophilic Electrodes Matter

• Gas Management: The NiFe/ATNT (annealed TiO₂ nanotube) electrode exhibits zero water contact angle and 155° underwater O₂ contact angle, facilitating formation of tiny 23 µm bubbles that detach rapidly compared to 124 µm bubbles on conventional Ti felt.
• Electrochemical Performance: Demonstrates oxygen evolution reaction overpotential of 235 mV at 10 mA cm^-2 with a Tafel slope of 60 mV dec^-1 in 1.0 M KOH, outperforming commercial IrO₂ catalysts.
• Device-Level Impact: When integrated into AEMWE with Pt/C cathode, delivers 1.67 A cm^-2 at 1.80 V and consumes only 4.05 kWh Nm^-3 H₂—surpassing most reported systems and approaching IRENA’s 2050 target.
• Longevity: Operates continuously for 1 500 hours at 0.50 A cm^-2 and 80 °C with degradation rate of merely 0.20 mV h^-1, while hydrophobic counterparts fail within 500 hours due to bubble-induced dead zones.

Innovative Design & Features

• Hierarchical Nanotube Architecture: Anodization and 500 °C annealing of Ti felt creates 3-D porous anatase TiO₂ nanotubes with 120 nm surface roughness, providing abundant nucleation sites for uniform NiFe nanoparticle deposition.
• Electronic Synergy: X-ray spectroscopy reveals electron transfer from TiO₂ to NiFe, creating electron-rich catalytic surfaces that enhance OER kinetics while maintaining structural integrity.
• Bubble Dynamics: Real-time imaging shows continuous bubble release without coalescence on ATNT surface, eliminating mass-transfer overpotentials that plague flat hydrophobic substrates.
• Versatility: Performance advantages maintained across different commercial membranes (PiperION, Fumasep) and electrolytes—from concentrated KOH to pure water.

Applications & Future Outlook

The study demonstrates that super-hydrophilic electrode design is crucial for simultaneous enhancement of activity, stability and efficiency in AEMWE systems. The NiFe/ATNT configuration achieves twice the current density of hydrophobic counterparts while eliminating bubble-related degradation pathways. Future research will focus on scaling the anodization process for large-area electrodes and extending the nanotube architecture to cathode materials for symmetric bubble management. This work provides a practical pathway toward durable, low-cost AEMWE stacks competitive with established alkaline and PEM technologies. Stay tuned for scale-up demonstrations from the multi-institutional Korea-China collaboration!