UNIAQ Department of Physics

Transcription

1 Nano4water, 2 nd dissemination Workshop Chalkidiki, April 2012 Dr. Luca Lozzi Department of Physics University of L Aquila Italy

2 UNIAQ Department of Physics N-doped TiO 2 nanostructured coatings for water purification Daniela Di Camillo, Fabrizio Ruggieri, Sandro Santucci, and Luca Lozzi Department of Physics, University of L Aquila, L Aquila, Italy Eda Cetinorgu-Goldenberg, Ines Chayoun, Reuven Avni, and Raymond L. Boxman Electrical Discharge and Plasma Laboratory, Tel Aviv University, Tel Aviv 69978, Israel Wilson Smith, Jerome Pulpytel, and Farzaneh Arefi-Khonsari Laboratoire de Génie des Procédés Plasma et Traitement de Surface, Université Pierre et Marie Curie, Paris 75231, France NATIOMEM (EU grant n , THANKS!) Nano-structured TiON Photo-Catalytic Membranes for Water Treatment Coating goup contribution

3 TiO 2 - Semiconductor : band gap ev - Different crystalline phases: Anatase, Rutile, Brookite - Highly reactive surface: surface defects and dangling bond - Wide literature survay on photocatalstic properties - Biologically and chemically inert - Stable with respect to photocorrosion and chemical corrosion - Inexpensive - Bactericide properties - Photoinduced hydrophilicity

4 Doped TiO 2 catalysts Asashi et al Science 2001

5 TiO 2 doping: absorption edge red shift The TiO 2 light absorption edge can shift to visible light by doping V doped (0 13%) TiO2 nanoparticles (Fu et al JPCB 2005). N-doped TiO2 nanoparticles (Dong et al JHM 2009)

6 Role of the coating groups - Deposition of N-doped TiO 2 by: - Filtered vacuum arc deposition (Tel Aviv University, IL) - RF sputtering (Pierre and Marie Curie Univ., Paris, F) - Sol-gel dip-coating (Univ. of L Aquila, I) - Electrospinning (Univ. of L Aquila, I) - Characterization (SEM, XPS, XRD, UV-VIS) - Photocatalytic tests (Methylene Blue degradation under visible light)

7 Filtered Vacuum Arc System (Tel Aviv Univ.) Vacuum Arc - a high current, low voltage discharge in vacuum between conducting electrodes. Produces 95% ionized beam with high ion charge (+2, +3) and high ion energies (~ 42 ev).

8 Transmission vs Wavelength plots for different N 2 % percentages. No substrate bias. Can shift absorption towards VIS. Transmission (%T) RF Plasma bias 50 W ( V bias) Wavelength (nm) 10% N2 70% N2 50% N2

9 Photocatalytic Test Procedure : Test molecule methylene blue (MB) dye 30 ml of 5 MB solution W 4 hours of irradiation under fluorescent light ( ) ~ 815 cm 2 Solar/ UV/ Fluorescent Lamp 50mm D= 90mm 3mm

10 % MB Removal 60 TiO 2 ZnO bi layer % N2

11 Summary of FVAD Results UNIAQ Department of Physics FVAD produced adherent, highly transparent TiO 2 thin films containing substitutional and interstitial nitrogen. Annealing: improved the photocatalytic activity (PCA) produced crystalline anatase phase increased N 2 and RF substrate bias shifted absorption edge wavelength up to 495 nm for films deposited on 500 o C substrates. But best monolayer PCA obtained with 0% N 2 Best PCA from TiO 2 ZnO bilayer

12 UPMC: Three Methods to Produce N-doped TiO 2 Dual Reactive Gas Sputtering UNIAQ Department of Physics TiO 2 /TiN Bi-layer TiN Oxidation Reactive gas: N 2, O 2 Reactive gas: N 2 Reactive gas: N 2 + O 2 Array TiO x N y Substrate 300 ~ 500 nm Substrate TiO 2 TiN Substrate TiO 2 TiO x N y TiN Substrate Homogeneous film Barrier TiN + TiO 2 Gradient TiN to TiO 2

13 Bi-Layer Deposition 1 sequence 2 Sequential introduction of the reactive gases sccm 0 2 O 2 t N N 2 O 2 O 2 Ti/Ar N/Ar O/Ar Total thickness of coatings was kept constant at 500 nm Number of layers Time (seconds) Optical emission spectra during deposition Thickness of layers

14 Photocurrent : Influence of TiN/TiO 2 ratio Best number of TiN/TiO 2 bi-layers : 18 but we can also change the TiN/TiO 2 ratio Example with 3 bi-layers TiO 2 TiN TiO 2 TiN TiO 2 TiN Substrate TiO 2 TiN TiO 2 TiN TiO 2 TiN Substrate Photocurrent (µa/cm 2 ) TiN/TiO 2 ratio 30% 20% 15% 10% 5% Time (seconds) Maximum Photocurrent (ma/cm 2 ) bi-layers TiN ratio % Highest photocurrent can be obtained for 18 bi-layers with 30% of TiN (TiN = 8 nm, TiO 2 = 16 nm for each bi-layer)

15 The Electrospinning technique and apparatus (UNIAQ) The electrospinning technique is a very simple and quite old (1 st patent on 1902!) method to deposit polymer and metal oxide micro- and nano-fibers. Syringe Polymer Solution Collector Needle High Voltage Power Supply Liquid Jet h = cm There are basically three components : 1. a needle with a relative small diameter (~ mm) connected to a syringe containing the solution; 2. collector (substrate); 3. high voltage power supply (10 50 KV). Taylor Cone

16 N-doped TiO 2 SEM N/Ti=1 500 /1 h air 16

17 MB degradation tests Fluorescent lamp C/C blank 600 C/1h air 500 C/1h air 400 C/1h air 300 C/1h air Electrospinning: N/Ti=1 MB concentration: 1mg/l buffer solution light source: fluorescent T=23 C C/C N-doped TiO 2 ES, N/Ti=1 MB concentration: 1mg/l light source: Fluorescent T= 23 C blank 400 C/1h air 400 C/1h air+550/3h N2 400 C/1h air+550 C NH Time (min) Time (min) N substitutional (NH3) does not increase the photocatalytic activity

18 Sol-gel dip - coating system (UNIAQ) Titanium(IV) butoxide ( Ti(OCH 2 CH 2 CH 2 CH 3 ) 4 ) Triethanolamine ( (HOCH 2 CH 2 ) 3 N )

19 Metallic membrane Metallic membrane + N-TiO2

20 UNIAQ Department of Physics Metallic membrane Metallic membrane + N-TiO2

21 XRD and XPS 150 C/12h+510 C/1h air 150 C/12h+510 C/1h+550 C/3h N C/12h+510 C/1h air 150 C/12h+510 C/1h air+550 C/3h N 2 N 1s Intensity (arb. units) anatase rutile TiO 2 N-doped /glass Sol-gel dip-coating XRD GI= 0.5 Intensity (arb. units) 150 C/12h+510 C/1h air+550 C/3h NH 3 TiO 2 N-doped /glass Sol-gel dip-coating Theta Binding Energy (ev)

22 MB Photocatalytic activity tests C/C Sol-gel dip coating MB concentration: 1mg/l buffer solution light source: fluorescent substrate: glass blank 600 C/1h air 500 C/1h air Time (min) C/C Sol-gel dip-coating MB concentration: 1mg/l light source: Fluorescent Substrate: glass blank 500 C/1h air 500 C/1h air+550/3h N2 500 C/1h air+550/3h NH Time (min)

23 C/C 0 UNIAQ Department of Physics MB Photocatalytic activity tests different substrates blank quartz 450 C/1h alumina 450 C/1h membrane 2um 450 C/1h Sol-gel dip-coating MB concentration: 1mg/l Volume 3ml buffer solution light source: fluorescent Time (min)

24 UNIAQ conclusions: - N-doped TiO2 surface using both ES and sol-gel - Anatase films with low N concentration (1-3%) - Nano-structured films - good MB degradation properties - Problems with the film adhesion (ES) - Effects of the substrate

25 Conclusions: - Different methods to deposit N-doped TiO2 films - Deposition of crystalline (anatase) films with low N concentration (2-5%) - Nano-structured films - All samples show good MB degradation properties - Effect of the substrate (mainly using chemical method) - Further tests on other compounds (CBZ) are in progress - In the next months the best method to prepare the samples for the pilot plant will be selected