Graduate School of EEWS and ‡KAIST Analysis Center, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, Korea.
Nano Lett. 2017 May 10;17(5):3126-3132. doi: 10.1021/acs.nanolett.7b00561. Epub 2017 Apr 11.
Atomic-scale direct probing of active sites and subsequent elucidation of the structure-activity relationship are important issues involving oxide-based electrocatalysts to achieve better electrochemical conversion efficiency. By generating Ruddlesden-Popper (RP) two-dimensional homologous faults via simple control of the cation nonstoichiometry in LaNiO thin films, we demonstrate that strong tetragonal distortion of [NiO] octahedra is induced by more than 20% elongation of Ni-O bonds in the faults. In addition to direct visualization of the elongation by scanning transmission electron microscopy, we identify that the distorted [NiO] octahedra in the faults show considerably higher electrocatalytic activities than other surface sites during the electrochemical oxygen evolution reaction. This unequivocal evidence of the octahedral distortion and its impact on electrocatalysis in LaNiO suggests that the formation of RP-type faults can provide an efficient way to control the octahedral geometry and thereby remarkably enhance the oxygen catalytic performance of perovskite oxides.
原子尺度直接探测活性位，并阐明结构-活性关系，这对于基于氧化物的电催化剂实现更好的电化学转化效率是非常重要的。通过简单地控制 LaNiO 薄膜中的阳离子非化学计量比，生成 Ruddlesden-Popper（RP）二维同系断层，我们证明了在断层中 Ni-O 键的伸长超过 20%，会导致[NiO]八面体的强四方畸变。除了通过扫描透射电子显微镜直接观察到伸长外，我们还确定在电化学析氧反应中，断层中畸变的[NiO]八面体比其他表面位具有更高的电催化活性。这一明确的证据表明，八面体畸变及其对 LaNiO 电催化的影响表明，RP 型断层的形成可以提供一种有效控制八面体几何形状的方法，从而显著提高钙钛矿氧化物的氧催化性能。
