RESUMO
LiFeOHS is a material with Li2(OH)2 layers intercalated between Fe2S2 planes. Its hydrothermal synthesis in various concentrations of LiOH yields materials with a high non-stoichiometry of the Li/Fe ratio which can be explained by partial substitution of Li+ for Fe2+ in the Li2(OH)2 layers. Thermogravimetry, X-ray diffraction and Mössbauer studies indicate that the charge balance is obtained by substitution of hydroxyl ions OH- by oxide ions O2-. This material has been tested as an electrode for lithium-ion batteries against lithium metal. Specific capacities above 200 mA h g-1 at C/10 are achieved, involving 1 lithium per chemical formula when cycled between 1 V and 3 V vs. lithium. The first irreversible discharge leads to the insertion of one lithium atom and the evolution of hydrogen gas while iron remains in its +2-oxidation state. An original Li2OFeS oxysulfide is formed. The following reversible oxidation/reduction cycles involve the Fe3+/Fe2+ redox couple between the two limiting compositions: Li2OFeIIS and LiOFeIIIS.
RESUMO
The formation of a new hybrid material based on titanium dioxide as inorganic support and containing an iron organochelator (ICL670) is described. An organophosphorous coupling agent was used to graft the organic molecule on the oxide surface. The attachment of the organic substrate was well-confirmed by FTIR (DRIFT), solid-state (31)P and (13)C CPMAS NMR, thermal analysis and the integrity of the structural and morphological parameters were verified using XRD and TEM analyses. The interaction between the material and dissolved iron(III) was also investigated through potentiometric measurements and demonstrated the interest of this new non-siliceous based hybrid material. The obtained linear evolution of the open circuit potential from 10(-2) to 10(-6) mol L(-1) can be used for the analytical detection of iron(III).