State-of-the-Art Materials Science in Belgium 2017

In this paper, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is
doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors
are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the
synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite
TiO2 nanoparticles of 6–8 nm are formed, with a specific surface area between 200 and 275 m2·g−1.
In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO2 nanoparticles
of 6–8 nm with a specific surface area between 185 and 240 m2·g−1 are obtained. X-ray photoelectron
spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in
TiO2 materials through Ti–O–N bonds allowing light absorption in the visible region. Photocatalytic
tests on the remediation of water polluted with p-nitrophenol show a marked improvement for all
doped catalysts under visible light. The optimum doping, taking into account cost, activity and ease
of synthesis, is up-scaled to a volume of 5 L and compared to commercial Degussa P25 material.
This up-scaled sample shows similar properties compared to the lab-scale sample, i.e., a photoactivity
4 times higher than commercial P25.