Unraveling Oxygen Evolution on Iron-Doped β‑Nickel Oxyhydroxide: The Key Role of Highly Active Molecular-like Sites

• Published in: Journal of the American Chemical Society Vol. 141; no. 1; pp. 693 - 705
• Main Authors: Martirez, John Mark P, Carter, Emily A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.01.2019
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b12386

The active site for electrocatalytic water oxidation on the highly active iron­(Fe)-doped β-nickel oxyhydroxide (β-NiOOH) electrocatalyst is hotly debated. Here we characterize the oxygen evolution reaction (OER) activity of an unexplored facet of this material with first-principles quantum mechanics. We show that molecular-like 4-fold-lattice-oxygen-coordinated metal sites on the (1̅21̅1) surface may very well be the key active sites in the electrocatalysis. The predicted OER overpotential (ηOER) for a Fe-centered pathway is reduced by 0.34 V relative to a Ni-centered one, consistent with experiments. We further predict unprecedented, near-quantitative lower bounds for the ηOER, of 0.48 and 0.14 V for pure and Fe-doped β-NiOOH(1̅21̅1), respectively. Our hybrid density functional theory calculations favor a heretofore unpredicted pathway involving an iron­(IV)-oxo species, Fe4+=O. We posit that an iron­(IV)-oxo intermediate that stably forms under a low-coordination environment and the favorable discharge of Ni3+ to Ni2+ are key to β-NiOOH’s OER activity.