A novel high entropy spinel-type aluminate MAl2_{2}O4_{4}(M = Zn, Mg, Cu, Co) and its lithiated oxyfluoride and oxychloride derivatives prepared by one-step mechanosynthesis

For the first time, a spinel-type high entropy oxide (Zn$_{0.25}$Cu$_{0.25}$Mg$_{0.25}$Co$_{0.25}$)Al$_{2}$O$_{4}$ as well as its derivative lithiated high entropy oxyfluoride Li$_{0.5}$(Zn$_{0.25}$Cu$_{0.25}$Mg$_{0.25}$Co$_{0.25}$)$_{0.5}$Al$_{2}$O$_{3.5}$F$_{0.5}$ and oxychloride Li$_{0.5}$(Zn$_{0.25}$Cu$_{0.25}$Mg$_{0.25}$Co$_{0.25}$)$_{0.5}$Al$_{2}$O$_{3.5}$Cl$_{0.5}$ are prepared in the nanostructured state via high-energy co-milling of the simple oxide precursors and the halides (LiF or LiCl) as sources of lithium, fluorine and chlorine. Their nanostructure is investigated by XRD, HR-TEM, EDX and XPS spectroscopy. It is revealed that incorporation of lithium into the structure of spinel oxide together with the anionic substitution has significant effect on its short-range order, size and morphology of crystallites as well as on its oxidation/reduction processes. The charge capacity of the as-prepared nanomaterials tested by cyclic voltammetry is found to be rather poor despite lithiation of the samples in comparison to previously reported spinel-type high entropy oxides. Nevertheless, the present work offers the alternative one-step mechanochemical route to novel classes of high entropy oxides as well as to lithiated oxyfluorides and oxychlorides with the possibility to vary their cationic and anionic elemental composition

Supramolecular-templated thick mesoporous titania films for dye-sensitized solar cells: Effect of morphology on performance

10.1021/am900529eACS Applied Materials and Interfaces1122789-279

Molecular scale characterization of the titania-dye-solvent interface in dye-sensitized solar cells

Charge separation at the dye/titania interface in dye sensitized solar cells is strongly influenced by the thickness and homogeneity of the sensitizing dye layer, as this controls the potential drop across the interface, and the probability of an excited electron being transferred from the dye to the titania. In this study we use atomic force microscopy and the depth profiling method neutral impact collision ion scattering spectroscopy (NICISS) to investigate the thickness and homogeneity of N719 dye adsorbed to titania before and after rinsing with pure acetonitrile. Both experimental methods show that the dye layers are closed but inhomogeneous. Inhomogeneity is more pronounced for unrinsed samples