NiOOH Exfoliation-Free Nickel Octahedra as Highly Active and Durable Electrocatalysts Toward the Oxygen Evolution Reaction in an Alkaline Electrolyte

• Published in: ACS applied materials & interfaces Vol. 10; no. 12; pp. 10115 - 10122
• Main Authors: Kim, Byeongyoon, Oh, Aram, Kabiraz, Mrinal Kanti, Hong, Youngmin, Joo, Jinwhan, Baik, Hionsuck, Choi, Sang-Il, Lee, Kwangyeol
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 28-03-2018
• Subjects: heteroepitaxy; oxygen evolution reaction; electrocatalyst; nickel oxyhydroxide; phase transformation
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.7b19457

A layered β-NiOOH crystal with undercoordinated facets is an active and economically viable nonnoble catalyst for the oxygen evolution reaction (OER) in alkaline electrolytes. However, it is extremely difficult to enclose the β-NiOOH crystal with undercoordinated facets because of its inevitable crystal transformation to γ-NiOOH, resulting in the exfoliation of the catalytic surfaces. Herein, we demonstrate {111}-faceted Ni octahedra as the parent substrates whose surfaces are easily transformed to catalytically active β-NiOOH during the alkaline OER. Electron microscopic measurements demonstrate that the horizontally stacked β-NiOOH on the surfaces of Ni octahedra has resistance to further oxidation to γ-NiOOH. By contrast, significant crystal transformation and thus the exfoliation of the γ-NiOOH sheets can be observed on the surfaces of Ni cubes and rhombic dodecahedra (RDs). Electrocatalytic measurements show that the β-NiOOH formed on Ni octahedra exhibits highly enhanced OER durability compared to the Ni cubes, Ni RDs, and the state-of-the-art Ir/C catalysts.