Recombination Catalyst Embedded Separators Enable a Wide Operating Window for High Pressure Alkaline Water...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Alkaline water electrolyzers (AWEs) are advancing with thinner separators for pressurized operation.
• Hydrogen (H2) crossover through separators remains a key limitation in AWEs, restricting operational pressure and window.
• Current AWE technology faces challenges in balancing efficiency with safety due to H2 crossover.

Purpose of the Study:

• To develop an advanced separator architecture for pressurized alkaline water electrolyzers.
• To mitigate hydrogen crossover by incorporating a recombination catalyst within the separator.
• To improve the safety and operational flexibility of AWE systems.

Main Methods:

• A novel separator was fabricated by spray-coating a platinum-based (Pt) recombination catalyst onto a reinforcing mesh, embedded in a polysulfone/zirconia matrix.
• The separator's thickness was optimized to 200 µm.
• Performance was evaluated by measuring hydrogen crossover and cell voltage at a current density of 1.0 A cm⁻².

Main Results:

• The developed separator demonstrated a 60% reduction in hydrogen crossover compared to commercial Zirfon 220.
• The AWE cell with the new separator achieved a lower cell voltage (1.78 V) than the cell with Zirfon 220 (1.84 V) at 1.0 A cm⁻².
• Stable operation was achieved, validating the internal recombination strategy, despite minor catalyst layer loss under dynamic load cycling.

Conclusions:

• Integrating a Pt-based recombination catalyst within a mechanically reinforced separator is a viable strategy to reduce hydrogen crossover in AWEs.
• This approach offers a practical and scalable solution for enhancing the safety and operational range of pressurized alkaline water electrolyzers.
• The developed separator architecture paves the way for more efficient and flexible AWE systems.