Dynamic Ionic Electrocatalysis for Oxygen Evolution: Synergistic Enhancement from Single Transition Metal Ions to...

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.