Growth and characterization of electrodeposited Na_(0.45)VOPO_4,1.58H_2O materials

摘要

The paper reports on a new and original way to prepare sodium vanadophosphate by using the electrochemical oxidation of vanadyl ions in H_3PO_4 solution to produce a deposit onto the electrode. Such a way insured an intimate mixing of the component elements in the solution allowing finer particles and high purity materials to be produced by rapid homogenous nucleation. The experimental conditions to obtain a pure phase are described in the paper. The main determining parameter is the solution pH which had to be adjusted at 1.9 or 2.0 with NaOH. A mixture of sodium vanadophosphate and V_2O_5, 0.5H_2O was obtained for higher pH = 2.2. A series of experiments including an X-ray diffraction study, thermogravimetric analysis, transmission electron microscopy and infrared spectroscopy investigation helped in determining the exact chemical formula of the obtained phase, i.e. Na_(0.45)VOPO_4,1.58H_20. The phase exhibits an orthorhombic structure with a = 8.85 A, b = 9.01 A and c = 13.02 A.