Understanding the Electronic Structure Evolution of Epitaxial LaNi<sub>1-<i>x</i></sub>Fe<sub><i>x</i></sub>O<sub>3</sub> Thin Films for Water Oxidation.
basic_science · Level V
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- Record sourced from PubMed, PMID 34546060.
- Also identified by DOI 10.1021/acs.nanolett.1c02901.
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Abstract
Rare earth nickelates including LaNiO<sub>3</sub> are promising catalysts for water electrolysis to produce oxygen gas. Recent studies report that Fe substitution for Ni can significantly enhance the oxygen evolution reaction (OER) activity of LaNiO<sub>3</sub>. However, the role of Fe in increasing the activity remains ambiguous, with potential origins that are both structural and electronic in nature. On the basis of a series of epitaxial LaNi<sub>1-<i>x</i></sub>Fe<sub><i>x</i></sub>O<sub>3</sub> thin films synthesized by molecular beam epitaxy, we report that Fe substitution tunes the Ni oxidation state in LaNi<sub>1-<i>x</i></sub>Fe<sub><i>x</i></sub>O<sub>3</sub> and a volcano-like OER trend is observed, with <i>x</i> = 0.375 being the most active. Spectroscopy and ab initio modeling reveal that high-valent Fe<sup>3+δ</sup> cationic species strongly increase the transition-metal (TM) 3d bandwidth via Ni-O-Fe bridges and enhance TM 3d-O 2p hybridization, boosting the OER activity. These studies deepen our understanding of structural and electronic contributions that give rise to enhanced OER activity in perovskite oxides.