Common-Ion Effect Triggered Highly Sustained Seawater Electrolysis with Additional NaCl Production

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Developing efficient seawater electrolysis systems is crucial for mass hydrogen production due to abundant seawater resources.
• Continuous seawater electrolysis leads to increased sodium chloride concentration, causing electrode corrosion and chlorine evolution.
• Existing methods struggle with stability and efficiency in high-salinity conditions.

Purpose of the Study:

• To develop a stable and efficient seawater electrolysis system for mass hydrogen production.
• To mitigate electrode corrosion and chlorine evolution issues in high-salinity electrolytes.
• To leverage the common-ion effect for enhanced performance and durability.

Main Methods:

• Utilizing the common-ion effect by adding 6 M sodium hydroxide (NaOH) to decrease sodium chloride (NaCl) solubility.
• Employing a ternary nickel-cobalt-iron phosphide (NiCoFe) as a bifunctional anode and cathode.
• Conducting electrolysis in simulative and Ca/Mg-free seawater under high current densities (500 mA/cm²).

Main Results:

• The addition of 6 M NaOH halved NaCl solubility, enabling sustained electrolysis in NaCl-saturated electrolytes.
• The NiCoFe phosphide electrode demonstrated stable operation for over 100 hours at 500 mA/cm².
• Achieved triple production of hydrogen (H₂), oxygen (O₂), and crystalline NaCl, with eliminated anode corrosion and chlorine evolution.

Conclusions:

• The common-ion effect effectively suppresses NaCl solubility, preventing corrosion and chlorine evolution during continuous seawater electrolysis.
• Ternary NiCoFe phosphide exhibits excellent bifunctional catalytic activity and stability in high-salinity electrolytes.
• This approach offers a promising pathway for efficient and durable hydrogen production from seawater.