On the synthesis of monovalent, divalent and trivalent element vanadates

Abstract

A chimie douce method has been used to prepare vanadates ( V5+) of various elements, trivalent (Al, Cr, Fe, In, Y, Bi), divalent (Co, Ni), monovalent (Li, Tl ), and a combination of nickel and lithium. By varying several parameters, especially the pH during the synthesis, several types of vanadates have been obtained ranging from orthovanadates ( VO 4 3−) to decavanadates ( V 10 O 28 6−). The pH conditions required to prepare the various vanadates fall nicely within the expectations of the previously reported cation charge-pH diagram.

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VOx/CrOx/Al2O3 Catalysts

“…35,36 In the breadth of this band for 10V12CrAl and 12Cr10VAl and in the absence of CrVO 4 , diffraction lines for these samples suggest that the CrVO 4 domains are disordered and highly dispersed. 27,[37][38][39] The 820 cm -1 band may reflect the presence of polychromates, polyvanadates, or mixed V-O-Cr oligomers, but its specific origin remains unclear. Figure 2 shows X-ray absorption near-edge spectroscopy (XANES) spectra for 10VAl, 12CrAl, 10V12CrAl, and 12Cr10VAl after treatment at 773 K for 2 h in flowing dry air and for three crystalline compounds V 2 O 5 , CrO 3 , Cr 2 O 3 .…”

“…Crystalline bulk CrVO 4 was prepared using the method proposed by Touboul and co-workers. 28, 29 Nitric acid (3N, EM Science, GR) was added to an aqueous solution of Cr(NO 3 ) 3 and NH 4 VO 3 to give a pH of 1 and then was refluxed at 333 K for 6 h. The precipitate was filtered and washed with 300 mL of deionized water, dried at 393 K overnight in ambient air, and then treated in flowing dry air (Airgas, zero grade, 1.67 cm 3 s -1 ) at 1073 K for 6 h. The X-ray diffraction (XRD) pattern of the as-synthesized sample was measured with a Siemens D5000 unit at ambient temperature using CuKR radiation, an X-ray tube operating at 45 kV and 35 mA, and a scan rate of 1.2°min -1 . Crystalline CrVO 4 -I was identified by comparison with literature XRD patterns.…”

Synthesis and Crystal Structure of Ni(VO3)2·4H2O and α-Ni(VO3)2·2H2O

“…These results stimulated our interest in the search for new electrode materials among the divalent-element vanadates. The synthesis process was adapted (8) and led to a substantial number of compounds giving electroactive vanadates, either new or previously prepared by other methods (9,10). Some of the new materials were obtained as single crystals.…”

Synthesis and electrochemical properties of InVO4nanotube arrays

“…This dissolution-reprecipitation process can be applied to synthesizing a large variety of monovalent, divalent and trivalent vanadates. 10 Although all the above methods facilitate the synthesis of pure and different phases of InVO 4 , the products are in powder form. substrates were boiled in water for a few hours to ensure a hydrophilic surface.…”