Fe-containing transition-metal (oxy)hydroxides are highly active oxygen-evolution reaction (OER) electrocatalysts in alkaline media and ubiquitously form across many materials systems. The study shows that Fe incorporation into Ni or Co (oxy)hydroxides depends on electrochemical history and host material structure. Substantially less Fe incorporates at anodic potentials past the Ni2+/3+ redox wave compared to potential cycling. Fe adsorbed under constant anodic potentials shows high per-Fe OER turnover frequency (~40 s−1 at 350 mV overpotential), attributed to under-coordinated "surface" Fe. TOF increases linearly with Fe concentration, suggesting a cooperative Fe site mechanism in FeOx clusters. DFT calculations support this, showing that neighboring Fe atoms in Fe-O-Fe clusters share and stabilize positive charge during oxidation of intermediates.

Yingqing Ou, Liam P. Twight, Bipasa Samanta, Lu Liu, Santu Biswas, Jessica L. Fehrs, Nicole A. Sagui, Javier Villalobos, Joaquín Morales-Santelices, Denis Antipin, Marcel Risch, Maytal Caspary Toroker, Shannon W. Boettcher