Detection of high-valent iron species in alloyed oxidic cobaltates for catalysing the oxygen evolution reaction.
basic_science · Level V
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- Record sourced from PubMed, PMID 34244515.
- Also identified by DOI 10.1038/s41467-021-24453-6 and PMC identifier 8270959.
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Abstract
Iron alloying of oxidic cobaltate catalysts results in catalytic activity for oxygen evolution on par with Ni-Fe oxides in base but at much higher alloying compositions. Zero-field <sup>57</sup>Fe Mössbauer spectroscopy and X-ray absorption spectroscopy (XAS) are able to clearly identify Fe<sup>4+</sup> in mixed-metal Co-Fe oxides. The highest Fe<sup>4+</sup> population is obtained in the 40-60% Fe alloying range, and XAS identifies the ion residing in an octahedral oxide ligand field. The oxygen evolution reaction (OER) activity, as reflected in Tafel analysis of CoFeO<sub>x</sub> films in 1 M KOH, tracks the absolute concentration of Fe<sup>4+</sup>. The results reported herein suggest an important role for the formation of the Fe<sup>4+</sup> redox state in activating cobaltate OER catalysts at high iron loadings.