期刊
MOLECULES
卷 28, 期 13, 页码 -出版社
MDPI
DOI: 10.3390/molecules28134945
关键词
layered titanates; structural features; H2O2 decomposition; catalysis; kinetics and mechanism
It has been found that potassium polytitanate powder (PPT) synthesized at 500°C by treating powdered TiO2 with a mixture of KOH and KNO3 is a low-cost and efficient catalyst for the decomposition of H2O2 in aqueous solutions. The catalytic activity of PPT depends on the weight ratio of [TiO2]:[KOH]:[KNO3], and increases with the amount of KNO3. This increase in catalytic activity is attributed to the increased concentration of Ti4+-O(H)-Ti4+ groups on the surface of PPT.
It is shown that the potassium polytitanate powder (PPT) synthesized at 500 & DEG;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.
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