Catalytic Decomposition of H2O2 in the Aqueous Dispersions of the Potassium Polytitanates Produced in Different Conditions of Molten Salt Synthesis.

Abstract

It is shown that the potassium polytitanate powder (PPT) synthesized at 500 °C via the treatment of powdered TiO2 (rutile) in molten mixtures of KOH and KNO3 is a cheap and effective catalyst of H2O2 chemical decomposition in aqueous solutions. At the same time, the PPT catalytic activity strongly depends on the [TiO2]:[KOH]:[KNO3] weight ratio in the mixture used for the synthesis, increasing with [KNO3] in the order of PPT (30:30:40) < PPT (30:50:20) < PPT (30:70:0). The obtained results are explained by increased [Ti3+] in the PPT structure (XPS data), which is grown in this order from 0 to 4.0 and 21.9 at.%, respectively, due to the reduced oxidation activity of the melt used for PPT synthesis. The mechanism of the autocatalytic process taking place in the PPT-H2O2-H2O system is analyzed. Taking into account the data of FT-IR spectroscopy, it is assumed that the increased catalytic activity of the investigated materials is related to the increased surface concentration of the Ti4+-O(H)-Ti4+ groups, formed from the Ti3+-O(H3O+)-Ti4+ clusters and further transformed into Ti-O-O-H catalytic centers. Some possible applications of the PPT-H2O2-H2O catalytic system, including the oxidation processes of green chemistry and photo-catalysis, are discussed.