resumo
Nitrogen-doped TiO2 nanoparticles with high specific surface area and photocatalytic activity under visible light were successfully produced using a modified sol-gel method with urea introduced as the nitrogen source. Different synthesis approaches and parameters such as doping temperature and urea to TiO2 molar ratio were tested to examine the best outcome regarding photocatalytic activity for both UV-A and visible light irradiation. UV-vis diffuse reflectance characterization revealed a decrease in band gap from 3.24 to a minimum of 2.79 eV with the N-doping process. The photocatalytic Methylene Blue dye degradation assays suggests that the introduction of nitrogen in the TiO2 lattice cell can provide a higher efficiency under both UV-A and visible irradiation. The maximum photocatalytic activity was achieved for the nitrogen-doped powders prepared with the lowest urea:TiO2 molar ratio (1.5) as it was the formulation that promoted an enhancement in N-doping and particle specific surface area to 182 m(2) g(-1), despite the fact that the highest specific surface area was registered for undoped TiO2 nanoparticles (228 m(2) g(-1)). A synthesis step variation was performed to enhance the specific surface area of nanoparticles and consequently the photocatalytic activity. This modification promoted an increase in specific surface area by a factor of similar to 5. XPS spectra confirmed a successful introduction of nitrogen in the TiO2 lattice up to 1.5 at.% for optimized powders, which is strongly dependant of the type of synthesis and the amount of dopant species added during the doping process.
palavras-chave
TITANIUM-DIOXIDE; SOL-GEL; PHOTOACTIVITY; HYDROLYSIS; REDUCTION; ORIGIN
categoria
Chemistry; Engineering
autores
Marques, J; Gomes, TD; Forte, MA; Silva, RF; Tavares, CJ
nossos autores
Rui Ramos Ferreira e Silva
Professor associadoagradecimentos
The authors acknowledge the financial support of the project NanoPlus Window, with the reference POCI-01-0247-FEDER-018018, co-funded by the European Regional Development Fund (ERDF), through the Operational Programme for Competitiveness and Internationalisation (COMPETE 2020), under the PORTUGAL 2020 Partnership Agreement. J. Marques acknowledges the pH.D grant from FCT (reference SFRH/BD/112868/2015). This work was also developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement.