Department of Chemistry, Temple University , Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.
Center for the Computational Design of Functional Layered Materials (CCDM), Temple University , Philadelphia, Pennsylvania 19122, United States.
J Am Chem Soc. 2017 Feb 8;139(5):1863-1870. doi: 10.1021/jacs.6b09184. Epub 2017 Jan 30.
We investigated the dependence of the electrocatalytic activity for the oxygen evolution reaction (OER) on the interlayer distance of five compositionally distinct layered manganese oxide nanostructures. Each individual electrocatalyst was assembled with a different alkali metal intercalated between two nanosheets (NS) of manganese oxide to form a bilayer structure. Manganese oxide NS were synthesized via the exfoliation of a layered material, birnessite. Atomic force microscopy was used to determine the heights of the bilayer catalysts. The interlayer spacing of the supported bilayers positively correlates with the size of the alkali cation: NS/Cs/NS > NS/Rb/NS > NS/K/NS > NS/Na/NS > NS/Li/NS. The thermodynamic origins of these bilayer heights were investigated using molecular dynamics simulations. The overpotential (η) for the OER correlates with the interlayer spacing; NS/Cs/NS has the lowest η (0.45 V), while NS/Li/NS exhibits the highest η (0.68 V) for OER at a current density of 1 mA/cm. Kinetic parameters (η and Tafel slope) associated with NS/Cs/NS for the OER were superior to that of the bulk birnessite phase, highlighting the structural uniqueness of these nanoscale assemblies.
我们研究了氧析出反应（OER）的电催化活性对五种不同组成的层状氧化锰纳米结构层间距离的依赖性。每个单独的电催化剂都由不同的碱金属插层在氧化锰纳米片（NS）的两层之间形成双层结构。氧化锰 NS 通过层状材料软锰矿的剥落合成。原子力显微镜用于确定双层催化剂的高度。支撑双层的层间间距与碱金属阳离子的大小呈正相关：NS/Cs/NS > NS/Rb/NS > NS/K/NS > NS/Na/NS > NS/Li/NS。使用分子动力学模拟研究了这些双层高度的热力学起源。OER 的过电势（η）与层间间距相关；对于 OER，NS/Cs/NS 的 η（0.45 V）最低，而 NS/Li/NS 的 η（0.68 V）最高，电流密度为 1 mA/cm。与 OER 相关的 NS/Cs/NS 的动力学参数（η和塔菲尔斜率）优于体相软锰矿相，突出了这些纳米级组装体的结构独特性。
