1 PACCON 2013 Zinc Oxide Nanorods-Based Catalysts for Visible Light Photocatalysis Supamas Danwittayakul Mayuree Jaisai, Panida Muangkasem, Thammarat Koottatep 1

2 Outline 1. Introduction 2. Experimental 3. Results and Discussion 4. Conclusions 2

3 Introduction 3

Photocatalysis of Metal Oxide 4 Metal OxidesBandgap (eV) TiO ZnO3.4 MO hh hh hh hh hh hh e-e- e-e- e-e- e-e- e-e- e-e- Organic molecule OH  OH - O2-O2- CO 2 + H 2 O O2O2 4

5 Very low quantity of UV light in the solar spectrum Wavelength (nm) Photon Energy (eV) Radiation Energy (kW/m 2.nm) 5

 Increase an effective surface area  Manipulate defective sites in the structure Hypothesis 6

7 ZnO Nanorods Wurtzite structure 7 Hypothesis I

Phototcatalysis of Doped-Metal Oxide OH - OH  O2-O2- Organic molecule CO 2 + H 2 O h+h+ e-e- O2O2 e-e- e-e- e-e- e-e- h+h+ h+h+ h+h+ h+h+ MO 8 Hypothesis II

9 Experimental 9

10 Hydrothermal Growth of ZnO Repeat several cycles 350 o C Furnace 2 mM Zn(CH 3 COO) 2 Temp. >350  C Annealed at 350  C For 5 hr 350 o C Furnace 95 o C Oven [Zn(NO 3 ) 2 +HMT]: 5 mM Temp. 95  C for 15 hr Annealed at 350  C For 1 hr Seeding of ZnO Nanoparticles Growth of ZnO Nanorods 10

o C Furnace 95 o C Oven [Zn(NO 3 ) 2 +HMT]: 20 mM + MnC 4 H 6 O 4.4H 2 O Temp. 95  C for 15 hr Annealed at 350  C For 1 hr Mn doped ZnO nanorods Mn 2+ : 0.05%, 0.1%, 0.5%, 1%, 3% 11

12 Photocatalytic activity test C 0 – C C0C0 x 100 DE = ln(C/C 0 ) = - kt Degradation Efficiency Kinetic Calculation - Methylene blue aqueous solution : 1 x Molar - Nanocatalyst coated specimen size : 4 x 0.5 x 1 cm - Quartz cuvette volume : 7.5 ml - Tungsten-halogen light source (275 W) with klux intensity 12

13 Results & Discussion 13

14 Morphology of Pure ZnO Nanorods ZnO 1 mM 130nm, 1.4μm ZnO 5mM 130nm, 1.6μm ZnO 10mM 130nm, 1.7μm ZnO 20mM 154nm, 2μm 14

Dimension of ZnO Nanorods 15

16 Photocatalytic Activity of Pure ZnO Nanorods C 0 – C C0C0 x 100 DE = ln(C/C 0 ) = - kt Degradation % Time (min) 16

17 t 1/2 = haft life of first order reaction = ln(2)/k 17 Catalyst S.S.A (m 2 /g) Degradation (%) R2R2 k (min -1 ) t 1/2 (min) ZnO 1mM ZnO 5mM ZnO 10mM ZnO 20mM  % photocatalytic activity can be enhanced by an increase of effective surface area Photocatalytic Activity of Pure ZnO Nanorods

18 Mn doped ZnO catalysts Mn 0.1% Mn 0.5%Mn 1%Mn 3% Mn 0.05%ZnO 20mM 18

19 Time (min) Degradation % C 0 – C C0C0 x 100 DE = ln(C/C 0 ) = - kt 19 Photocatalytic Activity of Mn doped ZnO Nanorods

20 Photocatalytic Activity of Mn Doped ZnO catalysts  4.76% photocatalytic activity can be enhanced upon using 0.05Mn/ZnO nanocomposites Catalyst Degradation (%) R2R2 k (min -1 ) t 1/2 (min) ZnO20mM Mn/ZnO Mn/ZnO Mn/ZnO Mn/ZnO Mn/ZnO

21 Conclusions ZnO nanorods on porous ceramic substrates were successfully synthesized through hydrothermal technique. ZnO catalyst with larger surface area (45m 2.g -1 ) is 16% more active than that lower surface area ZnO catalyst (35-39 m 2.g -1 ) An enhancement of 4.76% in the photocatalytic activity could be improved by doping pure ZnO nanorods with 0.05% Mn(II). Mn doped ZnO nanorods can be good candidates for visible photocatalysis. 21

Acknowledgements  National Research Council of Thailand (NRCT)  National Metal and Materials Technology Center (MTEC)  Asian Institute of Technology (AIT)  National Nanotechnology Center (NANOTEC) 22

23 Thank You For Your Attention 23

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26 Figure 2 Width and length of ZnO nanorods grown on porous ceramic substrate through hydrothermal process with different growth solution concentrations Width and length of ZnO nanorods grown on porous ceramic substrate through hydrothermal process with different growth solution concentrations 26