One-step, hydrothermal synthesis of nitrogen, carbon co-doped titanium dioxide (N,CTiO2) photocatalysts. Effect of alcohol degree and chain length as carbon dopant precursors on photocatalytic activity and catalyst deactivation

A one-step, hydrothermal method for the synthesis of nitrogen, carbon co-doped titanium dioxide (N,CTiO2) photocatalysts is demonstrated. The incorporation of nitrogen from ammonia and carbon from alcohols with different chain length (methanol, ethanol, isopropanol, 1-butanol, 2-butanol, tert-butanol) used as carbon precursors was confirmed by FTIR/DRS and XPS analyses. The UV–vis/DR absorption spectra of the modified photocatalysts extended into the visible. XRD, BET and Zeta SizerNano techniques were used for the characterization of the modified photocatalysts. The crystallite size of N,CTiO2 was not affected by the nature of the alcohol or the pressure acquired during the modification process but surface area, particle size (crystal agglomerate) and anatase content increased with synthesis pressure. In contrast with other studies in literature, the photoactivity of the different synthesized materials was evaluated at a constant volumetric rate of photon absorption (VRPA) in an annular photoreactor. This innovative method allows the evaluation of the intrinsic photoactivity of each material. As a result, the effect of N,C-co-modification on the TiO2 photoactivity was evaluated without interference from the amount of radiation absorbed by each suspended powder since the total radiant energy absorbed by each slurry suspension was kept constant. Phenol decomposition confirmed that activity increased with the chain length of the alcohol precursor. The highest intrinsic photoactivity was for N,CTiO2 prepared from 2-butanol, and 1-butanol as carbon precursor which also exhibited much stronger resistance to deactivation during multiple catalyst reuse compared to pristine TiO2 and commercial Degussa P25 photocatalysts.

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► Optical and structural properties of N,CTiO2 depend on the alcohol precursor used.
► N,CTiO2 deactivates much less than TiO2 P25 and has much higher activity after reuse.
► A new approach for the evaluation of the intrinsic photocatalytic activity is proposed.
► Photocatalytic activity of slurries is measured at equal rate of photon absorption.