Synthesis of semiconductor nanoparticles applied in photocatalysis for the degradation of pollutants in aqueous and gas phase [Elektronische Ressource] / Víctor Manuel Menéndez Flores

Victor Manuel Menendez Flores

Informations

• Publié par: gottfried_wilhelm_leibniz_universitat_hannover
• Publié le: 01 janvier 2010
• Nombre de lectures: 17
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

Synthesis of Semiconductor Nanoparticles Applied in Photocatalysis for the
Degradation of Pollutants in Aqueous and Gas Phase



Von der Naturwissenschaftlichen Fakultät
der Gottfried Wilhelm Leibniz Universität Hannover
zur Erlangung des Grades


Doktor der Naturwissenschaften
-Dr. rer. nat.-


genehmigte Dissertation


von
Víctor Manuel Menéndez Flores
Maestro en Ingeniería, Ingeniero Químico
geboren am 23.07.1976, in Mexiko-Stadt


Hannover, 2010





















Referee: Prof. Dr. Thomas Scheper
Co-referee: Prof. Dr. Michael Wark
Day of PhD exam: 10.03.10


Index


Index

Index................................................................................................................................ i
Index of figures ............................................................................................................... v
Index of tables xi
Acknowledgements .......................................................................................................xii
Symbols and abbreviations ..........................................................................................xiii
Kurzfassung..................................................................................................................xvi
Abstract........................................................................................................................xvii
I. Introduction and Problem Statement ...................................................................... 1
II. Theory........................................................................................................................ 4
II.1. Fundamentals.......................................................................................................... 4
II.1.1. Semiconductor-interface behavior in absence of redox systems......................... 6
II.1.2. Semiconductor-interface behavior in presence of redox systems........................ 9
II.1.3. Behavior of illuminated semiconductor-interface................................................ 13
II.1.4. Photocatalytic reactions by charge transfer at semiconductor nanoparticles .... 19
II.1.5. Quantum size effect............................................................................................ 22
II.2. Heterogeneous photocatalysis .............................................................................. 23
II.2.1. Mechanisms ....................................................................................................... 24
II.2.2. Stability problems ............................................................................................... 26
II.3. New materials for photocatalysis........................................................................... 28
II.3.1. Photodeposited photocatalysts 28
II.3.2. Doped material ................................................................................................... 31
II.3.3. Heat treatment for structure modifications.......................................................... 32
II.4. Diverse photocatalytic test systems ...................................................................... 33
II.4.1. Self cleaning effect ............................................................................................. 34
II.4.2. Photocatalytic decomposition of DCA on bare TiO in aqueous phase ............. 36 2
II.4.3. Photocatalytic gas phase decomposition ........................................................... 38
iIndex

III. Materials and Methods.......................................................................................... 41
III.1. For deposition synthesis of Ag on TiO ................................................................ 41 2
+3III.2. For the S-doped TiO -Fe photocatalyst ............................................................. 41 2
III.3. For the synthesis of indium selenide .................................................................... 42
III.4. For the synthesis of beta gallium oxide 42
III.5. Set-up for photoactivity tests in aqueous phase, DCA degradation..................... 43
III.6. Measurements of pH, chloride ions and total organic carbon (TOC) ................... 45
III.7. Set-up for photoactivity tests in gas phase........................................................... 45
III.8. Set-up for carrying out photocurrent measurements............................................ 47
III.9. Set-up for cyclic voltammetry and Mott-Schottky measurements ........................ 47
IV. Results and Discussion........................................................................................ 49
IV.1. Photonic efficiency calculation ............................................................................. 49
IV.1.1. Photonic efficiency calculation for UV-A light.................................................... 49
IV.1.2. Photonic efficiency calculation modified for visible light intensity ..................... 49
IV.1.3. Photonic efficiency calculation for the gas phase system................................. 51
IV.2. Degussa P25 as a standard photocatalyst .......................................................... 53
IV.2.1. Degradation of DCA with bare Degussa P25 and its effect after washing........ 53
IV.2.2. Degradation of NO with Degussa P25............................................................. 55 x
IV.2.3. Degradation of acetaldehyde with Degussa P25 .............................................. 57
IV.3. Durability of Ag-TiO Photocatalysts Assessed for the Degradation of 2
Dichloroacetic Acid ....................................................................................................... 60
IV.3.1. Preparation of Ag-TiO and colloidal TiO photocatalyst .................................. 60 2 2
IV.3.2. Analysis and characterization of the Ag-TiO photocatalysts............................ 61 2
IV.3.3. Degradation of DCA with photodeposited silver on Degussa P25.................... 65
IV.3.4. Degrith self prepared colloidal TiO particles ........................ 67 2
IV.3.5. Total organic carbon Ag-TiO results ................................................................ 67 2
IV.3.6. Photonic efficiency Ag-TiO results................................................................... 71 2
IV.3.7. Conclusions....................................................................................................... 75
iiIndex

3+IV.4. Photocatalytic activities under visible light by S-doped TiO Fe photocatalyst .. 76 2
+3IV.4.1. Preparation of S-doped TiO -Fe photocatalyst............................................... 76 2
3+IV.4.2. Analysis and characterization of the S-doped TiO -Fe photocatalyst ............ 76 2
3+IV.4.3. Photocatalytic decomposition of DCA on S-doped TiO -Fe material ............. 82 2
3+IV.4.4. Degradation of DCA with S-doped TiO -Fe at pH 3 under visible light .......... 84 2
3+IV.4.5. Different pH values for degradation of DCA with S-doped TiO -Fe ............... 85 2
IV.4.6. Stability test by a consecutively DCA degradation reactions with S-doped TiO -2
3+Fe at diverse pH conditions ....................................................................................... 86
IV.4.7. Comparison of commercial photocatalysts under UV-A and visible light.......... 89
3+IV.4.8. Photocatalytic decomposition of NO or acetaldehyde on S-TiO -Fe x 2
nanoparticles under visible light in a gas phase reactor............................................... 91
3+IV.4.9. Photonic efficiency S-TiO -Fe results............................................................. 94 2
IV.4.10. Conclusions..................................................................................................... 96
IV.5. Solid state synthesis and characterization of In Se nanoparticles deposited by 2 3
heat treatment as a film electrode ................................................................................ 98
IV.5.1. Synthesis development of In Se and In Se nanocrystals............................. 100 2 3 6 7
IV.5.2. Analysis and characterization of the synthesized indium selenide material ... 101
IV.5.3. Mott-Schottky study of the In Se electrode.................................................... 111 2 3
IV.5.4. Current and photocurrent measurements of In Se electrode ........................ 114 2 3
IV.5.5. Conclusions..................................................................................................... 122
IV.6. Solid state synthesis of β -Ga O by heat treatment and characterized as a film 2 3
electrode or powder showing photocatalytic improvement decomposing acetaldehyde
.................................................................................................................................... 123
IV.6.1. Synthesis of gallium acetate ........................................................................... 124
IV.6.2. Synthesis and characterization of β-Ga O .................................................... 124 2 3
IV.6.3. Photocatalytic decomposition of acetaldehyde on β-Ga O nanoparticles under 2 3
UV-A light............................................................