Spectroscopic characterization of tungstated zirconia prepared by equilibrium adsorption from hydrogen peroxide solutions of tungsten(VI) precursors

Two series of WOx/ZrO2 samples are prepared by equilibrium adsorption from H2O2 solutions at pH 1.8 containing two different precursor anions, [W2O3(O2)4 (H2O)2]2– and [H2W12O40]6–. The starting material is amorphous zirconium oxyhydroxide. The maximum W densities obtained are larger than that reported in the literature for systems synthesized by the same method using aqueous non-peroxide solutions. In the case of the metatungstate precursor, this increase is attributed to the generation of additional anchoring sites by interaction between the amorphous support and H2O2. The high uptake achieved when the peroxo complex is used as a precursor is a result of both the ZrOx(OH)4-2x–H2O2 interaction and low nuclearity of the adsorbing anion. The materials are characterized by XRD, DR–UV–vis, Micro-Raman and FT-IR spectroscopy. The surface acidities of samples with identical W loading prepared by equilibrium adsorption from the [H2W12O40]6––H2O2 system and by impregnation with aqueous solution of ammonium metatungstate are investigated by FT-IR spectroscopy of CO adsorbed at 80 K.