ZnO/CTAB powder was prepared by microwave processing of a precipitate with the aid of cetyltrimethylammonium bromide (CTAB). The effects of CTAB on the crystal structure, morphology, optical and photo(electro)catalytic properties of ZnO particles were studied. The results showed that CTAB did not influenced crystal structure or phase purity of ZnO. However, even low concentration of CTAB vary particles morphology; cone-like particles were prepared by processing without CTAB, while a mixture of spheroidal and plate-like ZnO particles were produced when 0.001 M CTAB was used. It was found that synthesized ZnO powders have 0.10 eV lower band gap energy then bulk ZnO (3.37 eV). A high photocatalytic activity for decolorization of methylene blue water solution was established after 2 h of sunlight irradiation; efficiency was 100 and 67% for ZnO/CTAB and ZnO, respectively. Electrochemical test showed faster oxygen evolution kinetics when ZnO/CTAB was used as anode material. Enhanced photo(electro)catalytic activities of ZnO/CTAB particles are attributed to better absorption of visible light due to both, larger dimensions and surface sensitization by CTAB

Ahmetović, Sanita

Marković, Smilja

Rac, Vladislav

Stojadinović, Stevan

Stojković Simatović, Ivana

Uskoković, Dragan

Veselinović, Ljiljana

Škapin, Srečo Davor

English

ZnO/CTAB powder was prepared by microwave processing of a precipitate 
with the aid of cetyltrimethylammonium bromide (CTAB). The effects of 
CTAB on the crystal structure, morphology, optical and 
photo(electro)catalytic properties of ZnO particles were studied. The results 
showed that CTAB did not influenced crystal structure or phase purity of 
ZnO. However, even low concentration of CTAB vary particles morphology; 
cone-like particles were prepared by processing without CTAB, while a 
mixture of spheroidal and plate-like ZnO particles were produced when 0.001 
M CTAB was used. It was found that synthesized ZnO powders have 0.10 
eV lower band gap energy then bulk ZnO (3.37 eV). A high photocatalytic 
activity for decolorization of methylene blue water solution was established 
after 2 h of sunlight irradiation; efficiency was 100 and 67% for ZnO/CTAB 
and ZnO, respectively. Electrochemical test showed faster oxygen evolution 
kinetics when ZnO/CTAB was used as anode material. Enhanced 
photo(electro)catalytic activities of ZnO/CTAB particles are attributed to 
better absorption of visible light due to both, larger dimensions and surface 
sensitization by CTAB

RIMSI

       PHYSICAL CHEMISTRY 2018  14th International Conference on Fundamental and Applied Aspects of Physical Chemistry    Proceedings Volume I              September 24-28, 2018  Belgrade, Serbia   II  ISBN 978-86-82475-36-1 Title: Physical Chemistry 2018 (Proceedings)Editors: Željko Čupić and Slobodan Anić Published by: Society of Physical Chemists of Serbia, Studentski Trg 12-16, 11158, Belgrade, Serbia Publisher: Society of Physical Chemists of Serbia For Publisher: S. Anić, President of Society of Physical Chemists of Serbia Printed by: ʺJovanʺ, <Printing and Publishing Company, 200 Copies Number og pages: 550+6, Format B5, printing finished in September 2018 Text and Layout: ʺJovanʺ  Neither this book nor any part may be reproduced or transmitted in any form or by any means, including photocopying, or by any information storage and retrieval system, without permission in writing from the publisher.          200 - Copy printing                         III         CONTENT    Volume I  Organizer IV Comittes V Sponsors VI Plenary Lecture 1 Chemical Thermodynamics 57 Spectroscopy, Molecular Structure, Physical Chemistry of Plasma 71 Kinetics, Catalysis  157 Nonlinear Dynamics, Oscillatory Reactions, Chaos 253 Electrochemistry  361 Biophysical Chemistry, EPR investigations of biosystems, Photochemistry, Radiation Chemistry 419       IV       PHYSICAL CHEMISTRY 2018  14th International Conference on  Fundamental and Applied Aspects of Physical Chemistry     Organized by  The Society of Physical Chemists of Serbia  in co-operation with  Institute of Catalysis Bulgarian Academy of Sciences  and  Boreskov Institute of Catalysis Siberian Branch of   Russian Academy of Sciences  and  University of Belgrade, Serbia:  Faculty of Physical Chemistry Institute of Chemistry, Technology and Metallurgy Vinča Institute of Nuclear Sciences Faculty of Pharmacy Institute of General and Physical Chemistry, Belgrade, Serbia     V Organizing Committee  Chairman:   S. Anić (Serbia)  Vice-chairmans:  M. Gabrovska (Bulgaria) A. A. Vedyagin (Russia) S. N. Blagojević (Serbia)  Members: N. Cvjetičanin (Serbia), S. M. Blagojević (Serbia), M. Daković (Serbia), J. Dimitrić-Marković (Serbia), T. Grozdić (Serbia), Lj. Ignjatović (Serbia), D. Jovanović (Serbia),J. Jovanović (Serbia), M. Kuzmanović (Serbia), D. Marković (Serbia), B. Milosavljević (USA), M. Mojović (Serbia), N. Ostrovski (Serbia), N. Pejić (Serbia), M. Petković (Serbia), A. Popović-Bjelić (Serbia), B. Simonović (Serbia), D. Stanisavljev (Serbia), M. Stanković (Serbia), Z. Šaponjić (Serbia), B. Šljukić (Serbia), G. Tasić (Serbia), S. Veličković (Serbia), N. Vukelić (Serbia)  Scientific Committee  Chairman:   Ž. Čupić (Serbia) Vice-chairmans:  V. Bukhtiyarov (Russia)  S. Todorova (Bulgaria)  B. Adnađević (Serbia)  Members: S. Anić (Serbia), A. Antić-Jovanović (Serbia), D. J. Biswas (India), R. Cervellati (Italy), G. Ćirić-Marjanović (Serbia), V. Dondur (Serbia), S. D. Furrow (USA), A. Goldbeter (Belgium), R. Jerala (Slovenia), M. Jeremić (Serbia), A. Jovović (Serbia), Y. Kalvachev (Bulgaria), E. Kiš (Serbia), Lj. Kolar-Anić (Serbia), U. Kortz (Germany), T. Kowalska (Poljska), V. Kuntić (Serbia), G. Lente (Hungary), Z. Marković (Serbia), S. Mentus (Serbia), K. Novaković (UK), B. Novakovski (Poljska), S. Otto  (Netherlands), V. Parmon (Russia), R. Pascal (USA), M. Perić (Serbia), M. Plavšić (Serbia), J. Savović (Serbia), G. Schmitz (Belgium), I. Schreiber (Czech), L. Schreiberova (Czech), H. W. Siesler (Germany), E. M. Barbosa Souto (Portugal), N. Stepanov (Russia), E. Szabó (Slovakia), R. Tomovska (Spain), Á. Tóth (Hungary), M. Trtica (Serbia), V. Vasić (Serbia), D. Veselinović (Serbia), D. Vučković (Canada),  V. Vukojević (Sweden), P. Walde (Switzerland)  Local Executive Committee  Chairman:   S.N. Blagojević Vice-chairmans:  A. Ivanović-Šašić A. Stanojević  Members: M. Ajduković, I. N. Bubanja, A. Dobrota, J. Dostanić, D. Dimić, A. Ignjatović, S. Jovanović, Z. Jovanović, A. Jović, N. Jović-Jovičić, D. Lončarević, M. Kragović, J. Krstić, S. Maćešić, J. Maksimović, S. Marinović, V. Marković, D. Milenković, M. Milovanović, T. Mudrinić, B. Nedić, M. Pagnacco, A. Pavićević, N. Potkonjak, D. Ranković, M. Ristić,  B. Stanković, K. Stevanović,  M. Stević,  A. Stoiljković          PHYSICAL CHEMISTRY 2018    C-17-P   237 ENHANCED PHOTO(ELECTRO)CATALYTIC PROPERTIES OF ZnO PARTICLES SYNTHESIZED  BY CTAB-ASSISTED MICROWAVE PROCESSING   S. B.  1 - 2 21 3, V. Rac 4 5 1   1Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade, Serbia. (smilja.markovic itn.sanu rs  2University of Belgrade, Faculty of Physical Chemistry, Belgrade, Serbia. 3University of Belgrade, Faculty of Physics, Belgrade, Serbia. 4University of Belgrade, Faculty of Agriculture, Belgrade, Serbia.  5    ABSTRACT ZnO/CTAB powder was prepared by microwave processing of a precipitate with the aid of cetyltrimethylammonium bromide (CTAB). The effects of CTAB on the crystal structure, morphology, optical and photo(electro)catalytic properties of ZnO particles were studied. The results showed that CTAB did not influenced crystal structure or phase purity of ZnO. However, even low concentration of CTAB vary particles morphology; cone-like particles were prepared by processing without CTAB, while a mixture of spheroidal and plate-like ZnO particles were produced when 0.001 M CTAB was used. It was found that synthesized ZnO powders have 0.10 eV lower band gap energy then bulk ZnO (3.37 eV). A high photocatalytic activity for decolorization of methylene blue water solution was established after 2 h of sunlight irradiation; efficiency was 100 and 67% for ZnO/CTAB and ZnO, respectively. Electrochemical test showed faster oxygen evolution kinetics when ZnO/CTAB was used as anode material. Enhanced photo(electro)catalytic activities of ZnO/CTAB particles are attributed to better absorption of visible light due to both, larger dimensions and surface sensitization by CTAB.   INTRODUCTION Heterogeneous photocatalysis is recognized as an effective process for mineralization of a wide variety of organic and biological pollutants from drinking and wastewater [1]. Due to their high photoactivity and chemical inertness, semiconductors such as ZnO, TiO2, SnO2, etc. can be used to initiate photoreaction. Their application for the degradation of pollutants under direct sunlight irradiation is restricted by a wide band gap (> 3 eV),        PHYSICAL CHEMISTRY 2018    C-17-P   238 allowing the absorption of UV light only. Such disadvantage can be overcome 1]. In this research, CTAB was used as photo(electro)catalytic properties of ZnO powder was examined.   EXPERIMENTAL ZnO powders were prepared by microwave (MW) processing of a precipitate. The starting materials were ZnCl2, NaOH, and CTAB as a surfactant. After the dissolution of zinc chloride and CTAB, an adequate amount of the aqueous solution of NaOH was added dropwise, resulting in a white precipitate. The as-prepared suspension was MW processed for 5 min in a domestic oven (2.45 GHz, 800 W). The powders synthesized without and with surfactant are designated as ZnO and ZnO/CTAB, respectively. The phase purity and crystal structure were identified by XRD analysis (Philips PW 1050). The data were collected over a 2  range 10 70° with a step of 0.05° and a counting time of 5s. The particles morphology was observed by FE SEM (ULTRA plus, Carl Zeiss). Optical properties were studied by UV Vis diffuse reflectance (DR) (Thermo Scientific) and photoluminescence (PL) spectroscopy (Horiba Jobin Yvon).  The photocatalytic activity of ZnO particles was studied by the decolorization of methylene blue (MB) dye under direct sunlight irradiation. In each of the experiments 100 mg a powder was mixed with 100 ml of MB (10 ppm). Prior to sunlight irradiation, the suspension was magnetically stirred for 1 h in a dark to establish an adsorption-desorption equilibrium. Stirring was maintained during irradiation, too. At specific time intervals 3 ml of aliquots was withdrawn and centrifuged at 8000 rpm during 5 min. The concentration of MB after photocatalytic decomposition was determined by UV Vis spectrophotometry (GBC Cintra) in the wavelength range of 450750 nm. Electrochemical characterization was performed by the linear sweep voltammetry in the three-electrode quartz cell using Gamry PCI4/750. FTO glass coated by ZnO particles was used as the working electrode; Pt foil and saturated calomel electrode (SCE) were used as the counter and the reference electrode, respectively. An aqueous solution of 1 M KCl was used as the electrolyte. The scan rate was 20 mV·s-1.  RESULTS AND DISCUSSION The XRD patterns of ZnO and ZnO/CTAB particles are shown in Figure 1(a). The patterns indicate wurtzite hexagonal symmetry without other crystal phases or impurities. However, minor differences in the XRD patterns on their reflection ratios, especially on I(100)/I(002)/I(101), implicating the differently oriented crystallites growth. This assumption is confirmed by the        PHYSICAL CHEMISTRY 2018    C-17-P   239 FE SEM analyses, Figure 1(b-c). ZnO crystallites are organized in cone-shaped particles with the average length of 93 nm, while ZnO/CTAB powder is consisted of spheroidal particles with average diameter of 36 nm; the particles are scatterely organized in thin plate-like agglomerates with average width of 260 nm and thickness of 20 nm.    Figure 1. (a) XRD patterns, (b-c) FE SEM images of ZnO and ZnO/CTAB particles, respectively.  The optical properties of processed powders were examined by UV Vis DR and PL spectroscopy, Figure 2. In the visible light region ZnO/CTAB particles revealed 5% higher absorbance capacity than ZnO particles, Figure 2(a). The direct band gap energies, determined from Tauc plot, are about 3.25 eV with neglected difference. Two emission bands appeared in PL spectra of examined powders, Figure 2(b), at 410 and 620 nm, and can be attributed to surface and deep-level defects, respectively. PL spectra implicate that ZnO/CTAB particles contained larger number of surface defects than ZnO particles, while number of structural defects is reduced. Figure 2(c) shows the efficiency of the photocatalytic degradation of MB dye in the presence of examined powders. ZnO/CTAB shows 100% of efficiency after 2h of direct sunlight irradiation, while the efficiency of ZnO was 67%. The linear sweep voltammograms under dark was shown in Figure 2(d). The oxygen evolution potential values were 1.315 and 1.324 V vs. SCE for ZnO/CTAB and ZnO, respectively. Thus, applying ZnO/CTAB as anode reduces the potential value for oxygen evolution. Besides, the anodic current at 1.35 V vs. SCE was increased when ZnO/CTAB was used as anode, indicating faster oxygen evolution kinetics comparing with ZnO.         PHYSICAL CHEMISTRY 2018    C-17-P   240   Figure 2. (a) UV Vis DR spectra with inserted Tauc plots, (b) PL spectra of examined powders, (c) photocatalytic efficiency for the degradation of MB in the presence of examined powders, and (d) linear sweep voltammograms.  CONCLUSION ZnO/CTAB powder prepared by a microwave processing consists mixture of spheroidal and plate-like particles with distinguished amount of surface defects. The band gap energy of ZnO/CTAB powder is 3.25 eV; in the Vis range it absorbs up to 70% of the incident light intensity. The plate-like ined with surface defects enhanced visible-light absorption and promoted photocatalytic activity under direct sunlight irradiation. Applying of ZnO/CTAB as anode material reduces the potential for oxygen evolution and the oxygen evolution kinetics become faster.   Acknowledgement  This study was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, Grant no III45004.  REFERENCES [1] - Solar Energy, 2016, 127, 124-135. 

Enhanced photo(electro)catalytic properties of ZnO particles synthesized by CTAB-assisted microwave processing

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Enhanced photo(electro)catalytic properties of ZnO particles synthesized by CTAB-assisted microwave processing

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