New layered vanadium oxides MyH1-yV3O8 center dot nH(2)O (M = Li, Na, K) obtained by oxidation of the precursor H2V3O8

New layered vanadium oxides were prepared at room temperature via either electrochemical or chemical topotactic oxidation in aqueous media of the layered, solid precursor H2V3O8. Their formula MyH1 - yV3O8. nH(2)O (M = Li, Na, K) shows the oxidation of vanadium to occur with the removal of one hydrogen atom and with a partial exchange of the remaining proton. A structural study by powder X-ray diffraction, including a Rietveld analysis, clearly indicated that the structure of the anionic covalent layers, V3O8, are preserved in going from H2V3O8 to MyH1 - yV3O8. nH(2)O. In the latter compounds, all the water molecules occupy the interlayer space along with the M+ ions.