A Zero-Gap Electrolyzer Enables Supporting Electrolyte-Free Seawater Splitting for Energy-Saving Hydrogen Production

Area of Science:

• Electrochemistry
• Materials Science
• Renewable Energy

Background:

• Direct seawater splitting (DSS) offers a sustainable route for green hydrogen (H₂) production.
• Conventional DSS requires supporting electrolytes, leading to significant energy penalties (up to 12.5%) and operational challenges like precipitation and corrosion.
• Existing methods often necessitate pre-treatment of seawater, adding complexity and cost.

Purpose of the Study:

• To develop an energy-efficient DSS technology that operates without supporting electrolytes.
• To design a robust electrolyzer capable of stable operation in natural seawater, mitigating issues of precipitates and corrosion.
• To demonstrate a scalable and cost-effective method for green hydrogen production from saline water.

Main Methods:

• A zero-gap electrolyzer configuration was designed by integrating cation exchange membranes and bipolar membrane assemblies.
• The electrolyzer was operated in natural seawater without any added supporting electrolytes or chemical inputs.
• Performance was evaluated based on hydrogen and oxygen evolution, Faradaic efficiency, stability, and current density.

Main Results:

• The developed electrolyzer achieved stable direct seawater splitting without supporting electrolytes.
• It demonstrated nearly 100% Faradaic efficiency for H₂ production over 120 hours at a current density of 100 mA cm^-2.
• The integrated membrane system effectively managed precipitates and corrosion, creating an in-situ acidic-alkaline environment that facilitated reactions.

Conclusions:

• The zero-gap electrolyzer design successfully bypasses the energy penalty associated with supporting electrolytes in DSS.
• This technology offers a promising, energy-saving approach for green hydrogen production from low-grade saline water sources.
• The facile scalability and potential for volume-sensitive applications position this electrolyzer as a competitive alternative to pre-purification methods.