TY - JOUR

T1 - Mesoporous TiO2 nanocrystals as efficient photocatalysts

T2 - Impact of calcination temperature and phase transformation on photocatalytic performance

AU - Faycal Atitar, M.

AU - Ismail, A.A.

AU - Al-Sayari, S.A.

AU - Bahnemann, D.

AU - Afanasev, D.

AU - Emeline, A.V.

N1 - Funding information: M. Faycal Atitar gratefully acknowledges a scholarship from the The German Academic Exchange Service (DAAD) in the Frame of a Sandwich-Program. A.A. Ismail acknowledges the Alexander von Humboldt (AvH) Foundation for granting him a renewed research fellowship. Financial support from the Russian Foundation for Basic Research ( 13-03-90917 mol_in_nr) and the grant of the government of Russian Federation N 14.Z50.310016 are also gratefully acknowledged. Special thanks are due to Ms. Natalja Wendt of the Institut für Anorganische Chemie-, Uni-Hannover for her kind help in N 2 sorption measurements. TEM measurements performed by Prof. Dr. Armin Feldhoff of the Institut für Physikalische Chemie-Uni-Hannover is also gratefully acknowledged. The authors also thank Johannes Melcher and Imme Kretschmer from the Institut für Technische Chemie-Uni-Hannover for Raman and XRD measurements, respectively.

PY - 2015/3/5

Y1 - 2015/3/5

N2 - Mesoporous TiO 2 nanocrystals have been synthesized through sol gel method in presence of triblock copolymer as the structure directing agent. The as-prepared TiO 2 nanocrystals have been calcined at different temperatures, i.e., at 400°C, 500°C, 600°C, 700°C, and 800°C to demonstrate how their structural properties (morphology, mesoporosity, crystallite phases and sizes) affect the photocatalytic performance. The TEM images indicate that TiO 2 nanocrystals calcined at 500°C have a mesoporous structure with particle sizes of approximately 10-15nm. However, the TiO 2 calcined at 800°C shows a lower mesoporosity and particle sizes of ~75nm. The photocatalytic performance of the newly synthesized photocatalysts has been evaluated through the photodegradation of two different pollutants, i.e., the herbicide imazapyr and phenol, and has been compared to that of the commercially available nonporous Aeroxide TiO 2 P-25. For the imazapyr photodegradation, the newly synthesized mesoporous TiO 2 nanocrystals show an initial degradation rate around 2 times higher than the rate observed with the non-porous Aeroxide TiO 2 P25. The highest photocatalytic activity is observed for the samples calcined at 500°C followed by those calcined at 800°C. In contrast to that, a different behavior is found for the photodegradation of phenol. The results indicate that the TiO 2 samples calcined at 500°C show the highest photocatalytic activity for phenol photodegradation. It is proposed that the behavior of the photocatalysts in term of their photocatalytic efficiency and rate constants varies based on the pollutant type. TiO 2 calcined at 500°C can be considered as economically more efficient by saving energy through the lower temperature required in the calcination process.

AB - Mesoporous TiO 2 nanocrystals have been synthesized through sol gel method in presence of triblock copolymer as the structure directing agent. The as-prepared TiO 2 nanocrystals have been calcined at different temperatures, i.e., at 400°C, 500°C, 600°C, 700°C, and 800°C to demonstrate how their structural properties (morphology, mesoporosity, crystallite phases and sizes) affect the photocatalytic performance. The TEM images indicate that TiO 2 nanocrystals calcined at 500°C have a mesoporous structure with particle sizes of approximately 10-15nm. However, the TiO 2 calcined at 800°C shows a lower mesoporosity and particle sizes of ~75nm. The photocatalytic performance of the newly synthesized photocatalysts has been evaluated through the photodegradation of two different pollutants, i.e., the herbicide imazapyr and phenol, and has been compared to that of the commercially available nonporous Aeroxide TiO 2 P-25. For the imazapyr photodegradation, the newly synthesized mesoporous TiO 2 nanocrystals show an initial degradation rate around 2 times higher than the rate observed with the non-porous Aeroxide TiO 2 P25. The highest photocatalytic activity is observed for the samples calcined at 500°C followed by those calcined at 800°C. In contrast to that, a different behavior is found for the photodegradation of phenol. The results indicate that the TiO 2 samples calcined at 500°C show the highest photocatalytic activity for phenol photodegradation. It is proposed that the behavior of the photocatalysts in term of their photocatalytic efficiency and rate constants varies based on the pollutant type. TiO 2 calcined at 500°C can be considered as economically more efficient by saving energy through the lower temperature required in the calcination process.

KW - Calcination temperatures

KW - Herbicide imazapyr

KW - Mesoporous TiO

KW - Phenol

KW - Photodegradation

UR - http://www.scopus.com/inward/record.url?scp=84916608770&partnerID=8YFLogxK

U2 - 10.1016/j.cej.2014.11.075

DO - 10.1016/j.cej.2014.11.075

M3 - Article

VL - 264

SP - 417

EP - 424

JO - Chemical engineering journal

JF - Chemical engineering journal

SN - 1385-8947

ER -