Durable, pure water-fed, anion-exchange membrane electrolyzers through interphase engineering

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Energy

Background:

• Anion-exchange membrane water electrolyzers (AEMWEs) offer a promising route to scalable and cost-effective hydrogen production.
• A key limitation hindering AEMWEs is the electrochemical instability of anode ionomers, impacting operational durability.
• Current AEMWEs often require supporting electrolytes, adding complexity and cost.

Purpose of the Study:

• To enhance the durability of anion-exchange membrane water electrolyzers (AEMWEs) by addressing anode ionomer instability.
• To develop a method for stabilizing AEMWEs for operation in pure water, eliminating the need for supporting electrolytes.
• To investigate the mechanism of stabilization through interphase engineering using inorganic additives.

Main Methods:

• Interphase engineering using inorganic-containing molecular additives that coassemble with anode ionomers.
• Fabrication and testing of pure water-fed AEMWEs incorporating the engineered interphase.
• Electrochemical characterization, including durability testing at 2.0 amperes per square centimeter and 70°C.
• Analysis of additive-ionomer interactions and the formation of a protective interphase using various analytical techniques.

Main Results:

• Achieved a degradation rate of less than 0.5 millivolt per hour at 2.0 amperes per square centimeter and 70°C, representing a >20-fold durability improvement.
• Demonstrated stable operation of AEMWEs in pure water without supporting electrolytes.
• Identified that the stabilization mechanism involves cross-linking between metal oxo/hydroxo oligomers and ionomers, forming a protective interphase.
• Observed enrichment of the inorganic additive at the catalyst interface, passivating the anode ionomer against degradation while preserving mechanical integrity and conductivity.

Conclusions:

• Additive-based interphase engineering significantly enhances the durability of AEMWEs.
• This strategy enables AEMWEs to operate efficiently and stably in pure water, reducing operational costs and complexity.
• The developed approach is adaptable across diverse catalysts and ionomers, offering a versatile pathway for advancing electrochemical technologies.