Dynamic Ionic Electrocatalysis for Oxygen Evolution: Synergistic Enhancement from Single Transition Metal Ions to Bimetallic Activation in Alkaline Electrolytes

This study pioneers dynamic ionic catalysis for efficient oxygen evolution by engineering dissolved Fe(III), Co(II), and Ni(II) ions as self-regenerating active sites in alkaline electrolytes. In situ Raman/EIS diagnostics Fe(III) operates via a catalytic cycle Fe(III)(aq) → [Fe-OH]ads → [Fe-O]ads → [Fe-OOH]ads → Fe(III)(aq) + O₂, exhibiting superior activity on N-doped carbon nanotubes. Bimetallic systems reveal critical activity-stability trade-offs: Fe(III) + Co(II) delivers record performance but suffers 42% decay in 50 h due to CoOOH precipitation, while Fe(III) + Ni(II) maintains a 300 h stability through in situ activation and electrolyte replenishment. Multiscale characterization (TEM/X-ray photoelectron spectroscopy (XPS)/EIS) verifies (1) no solid catalyst formation; (2) Ni-induced Fe³⁺/Fe²⁺ ratio elevation to 1.30, enhancing the level of the O-O coupling; and (3) self-limiting precipitation in Fe/Ni systems. The Fe(III) + Ni(II) system demonstrates industrial viability with 100% Faradaic efficiency, establishing electrolyte engineering as a paradigm-shifting alternative to energy-intensive catalyst synthesis. This framework resolves fundamental activity-stability conflicts in electrocatalysis, enabling scalable green hydrogen production.