Benchmarking the pH-Stability Relationship of Metal Oxide Anodes in Anion Exchange Membrane Water Electrolysis

Anion exchange membrane water electrolysis (AEMWE) is one of the most promising technologies for producing green hydrogen; however, they still suffer from durability issues. One task is to find suitable electrolyte conditions for anode catalysts that endow them with both high activity and stability. Herein, we benchmark the pH-stability relationship of four typical metal oxides as anode catalysts in the AEMWE. Their electrochemical performance and structural stability were in-depth analyzed through impedance, dissolved composition in the electrolyte, and correlated Pourbaix diagram. NiFe₂O₄ with the best activity and stability in the strong alkaline (pH = 14) shows terrible stability in pure water, which is then verified due to the severe Fe leaching, and it cannot be alleviated by alkaline pre-activation. Notably, Co₃O₄ shows comparable activity and stability to IrO₂ in pure water and weak alkaline conditions. At pH = 12, it entails only ∼2.18 V to reach 1.0 A cm^-2 and stabilizes for 40 h, being superior to others. This work screens out suitable transition metal oxides as a substitute for noble metals and their optimal application scenarios for AEMWE.