TiO2 doping by hydroxyurea at the nucleation stage: towards a new photocatalyst in the visible spectral range
(2010) Physical Chemistry Chemical Physics — Vol. 12, n° 37, p. 11325-11334 (2010)
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- Abstract
- We report an original method of preparation of OCN-doped TiO2 for photocatalysis in the visible spectral range. The preparation is achieved by a sol-gel route using titanium tetraisopropoxide precursor. Special attention was paid to fluid micromixing, which enables homogeneous reaction conditions in the reactor bulk and monodispersity of the produced clusters/nanoparticles. The dopant hydroxyurea (HyU, CH4N2O2) is injected into the reactive fluid at the nucleation stage, which lasts tens of milliseconds. The doping results in a strong yellow coloration of the nanocolloids due to the absorption band in the spectral range 380-550 nm and accelerates the aggregation kinetics of both nuclei at the induction stage and sub-nuclei units (clusters) at the nucleation stage. FTIR, Raman and UV-visible absorption analyses show the formation of a stable HyU-TiO2 complex. EXAFS spectra indicate no appreciable changes of the first-shell Ti atom environment. The doping agent takes available surface sites of TiO2 clusters/nanoparticles attaining similar to 10% molar loading. The reaction kinetics then accelerates due to a longer collisional lifetime between nanoparticles induced by the formation of a weak =O ... Ti bond. The OCN-group bonding to titanium atoms produces a weakening of the C=O double bond and a strengthening of the C-N and N-O bonds.
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Azouani, R., Tieng, S., Chhor, K., Bocquet, J.-F., Eloy, P., Gaigneaux, E., Klementiev, K., & Kanaev, A. V. (2010). TiO2 doping by hydroxyurea at the nucleation stage: towards a new photocatalyst in the visible spectral range. Physical Chemistry Chemical Physics, 12(37), 11325-11334. https://doi.org/10.1039/b923548e (Original work published 2010)