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
The Electrochemical Energy, Catalysis, and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin, Strasse des 17. Juni 124, 10623, Berlin, Germany.
Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana, 47907, USA.
Nat Commun. 2020 May 20;11(1):2522. 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.
镍铁（NiFe）和钴铁（CoFe，MFe）层状双氢氧化物（LDHs）是碱性析氧反应（OER）中活性最高的电催化剂之一。在此，我们结合电化学测量、原位X射线散射和吸收光谱以及密度泛函理论（DFT）计算，以阐明催化活性相、反应中心和OER机理。我们提供了首个直接的原子尺度证据，即在施加阳极电位时，MFe LDHs从制备好的α相氧化为活化的γ相。OER活性γ相的特征是晶格间距收缩约8%以及插层离子的转变。DFT计算表明，OER通过Mars van Krevelen机理进行。表面铁位点的灵活电子结构，以及它们通过形成O桥连的Fe-M反应中心与最近邻M位点的协同作用，稳定了在纯M-M中心和单个铁位点上不利的OER中间体，从根本上解释了MFe LDHs的高催化活性。
