Various organic compounds can be decomposed in aqueous solution in the presence of TiO2 powders under irradiation with near ultraviolet light into carbon dioxide and water. The photocatalytic reaction takes place on the surface of the TiO2 particles. When titanium dioxide (TiO2) absorbs ultraviolet radiation from sunlight or is illuminated by a light source, it will produce pairs of electrons and holes. Because oxygen is not strongly adsorbed on semiconductor surfaces in contact with aqueous electrolytes, it is nearly impossible for an electron not to recombine if it remains free on the particle. Consequently, to keep the photooxidation process going, it is necessary to avoid accumulation of the electrons on particles to ultimately avoid their recombination with the holes. Hydrotalcite has a particular structure that is hypothesized to eliminate the rapid recombination of excited electrons/holes during the photoreaction. Hydrotalcite is a lamellar mixed hydroxide, relatively easy and inexpensive to synthesize in the laboratory. Its structure is based on stacking of positively charged layers with anions and water that confers relatively high mobility to the anions. Hydrotalcites are represented by the general formula [Mg(II)1-xAl(III)x(OH)2]x+(Ax/m)m-lnH2O, where Am- is a compensating anion. The TiO2 component of the hydrotalcite–enhanced TiO2 composite has been synthesized using Titanium (IV) isopropoxide, via sol-gel process, whilst the hydrotalcite constituent was generated starting from the corresponding Mg(II) and Fe(III) nitrates, in situ, using urea. Composites have been tested for photocatalytic decomposition of vanillin, showing a high conversion rate into carbon dioxide and water. The photocatalytic test reaction was performed under visible light (575 nm), using vanillin as phenol-model compound. The nanosized composites have been found very effective, displaying high conversion rates of vanillin into carbon dioxide and water.

Nitrogen and Iron(III) doped TiO2-hydrotalcite composites, synthesis and photocatalytic properties

256th National Meeting (2018)

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