• Anion modification offers a promising route to enhance OER catalyst stability and activity against chloride-ion corrosion in direct seawater electrolysis.
• A novel anion selection framework based on adsorption energy, ionic potential, and acid-base character guides the design of robust seawater electrolysis catalysts.
• The review identifies key stability mechanisms (external anion introduction, Cl−/OH− regulation) and activity mechanisms (electronic structure modulation, active species engineering, mass transfer optimization).
• Direct seawater electrolysis emerges as a cost-effective, sustainable alternative to desalination-based hydrogen production, with challenges in long-term durability remaining.