Cooperative Fe sites on transition metal (oxy)hydroxides drive high oxygen evolution activity in base.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38001061.
- Also identified by DOI 10.1038/s41467-023-43305-z and PMC identifier 10673886.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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 complexity and dynamics of the Fe sites within the (oxy)hydroxide have slowed understanding of how and where the Fe-based active sites form-information critical for designing catalysts and electrolytes with higher activity and stability. We show that where/how Fe species in the electrolyte incorporate into host Ni or Co (oxy)hydroxides depends on the electrochemical history and structural properties of the host material. Substantially less Fe is incorporated from Fe-spiked electrolyte into Ni (oxy)hydroxide at anodic potentials, past the nominally Ni<sup>2+/3+</sup> redox wave, compared to during potential cycling. The Fe adsorbed under constant anodic potentials leads to impressively high per-Fe OER turn-over frequency (TOF<sub>Fe</sub>) of ~40 s<sup>-1</sup> at 350 mV overpotential which we attribute to under-coordinated "surface" Fe. By systematically controlling the concentration of surface Fe, we find TOF<sub>Fe</sub> increases linearly with the Fe concentration. This suggests a changing OER mechanism with increased Fe concentration, consistent with a mechanism involving cooperative Fe sites in FeO<sub>x</sub> clusters.