In-situ structure and catalytic mechanism of NiFe and CoFe layered double hydroxides during oxygen evolution

• Published in: Nature communications Vol. 11; no. 1; pp. 2522 - 1-2522-10
• Main Authors: Dionigi, Fabio, Zeng, Zhenhua, Sinev, Ilya, Merzdorf, Thomas, Deshpande, Siddharth, Lopez, Miguel Bernal, Kunze, Sebastian, Zegkinoglou, Ioannis, Sarodnik, Hannes, Fan, Dingxin, Bergmann, Arno, Drnec, Jakub, Araujo, Jorge Ferreira de, Gliech, Manuel, Teschner, Detre, Zhu, Jing, Li, Wei-Xue, Greeley, Jeffrey, Cuenya, Beatriz Roldan, Strasser, Peter
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20.05.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 639/301/299/886; 639/638/563/979; 639/638/675; 639/638/77/886; Absorption spectroscopy; Catalytic activity; Chemical engineering; Chemistry; Contraction; Density functional theory; electrocatalysis; Electrocatalysts; Electrochemistry; Electronic structure; energy; Evolution; Gamma phase; Humanities and Social Sciences; Hydroxides; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Intermediates; Intermetallic compounds; Iron compounds; Laboratories; Mars surface; Materials science; Mathematical analysis; multidisciplinary; Nearest-neighbor; Nickel compounds; Oxygen; Oxygen evolution reactions; Phase transitions; Physics; Reaction centers; Science; Science (multidisciplinary); X-ray scattering; REDOX STATES; STABILITY; TRACKING; WATER OXIDATION; OXYHYDROXIDE ELECTROCATALYSTS; REACTION DYNAMICS; ACTIVITY TRENDS; TRANSITIONS; ALKALINE; RATIONAL DESIGN
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-16237-1

NiFe and CoFe (MFe) layered double hydroxides (LDHs) are among the most active electrocatalysts for the alkaline oxygen evolution reaction (OER). Herein, we combine electrochemical measurements, operando X-ray scattering and absorption spectroscopy, and density functional theory (DFT) calculations to elucidate the catalytically active phase, reaction center and the OER mechanism. We provide the first direct atomic-scale evidence that, under applied anodic potentials, MFe LDHs oxidize from as-prepared α-phases to activated γ-phases. The OER-active γ-phases are characterized by about 8% contraction of the lattice spacing and switching of the intercalated ions. DFT calculations reveal that the OER proceeds via a Mars van Krevelen mechanism. The flexible electronic structure of the surface Fe sites, and their synergy with nearest-neighbor M sites through formation of O-bridged Fe-M reaction centers, stabilize OER intermediates that are unfavorable on pure M-M centers and single Fe sites, fundamentally accounting for the high catalytic activity of MFe LDHs. NiFe and CoFe layered double hydroxides are among the most active electrocatalysts for the alkaline oxygen evolution reaction. Here, by combining operando experiments and rigorous DFT calculations, the authors unravel their active phase, the reaction center and the catalytic mechanism.