INVESTIGATION OF PHOTOCATALYTIC EFFECT OF TANTALUM DOPED
ANODIC TIN THIN FILMS
KIPROP SUMBA
A Research Proposal submitted to the Institute of postgraduate studies of Kabarak
University in
partial fulfillment of the Requirements for the Award of the Master of Science Degree
KABARAK UNIVERSITY
SEPTEMBER 2021
ii
DECLARATION
I hereby declare that this research is my original work and has not been submitted to any
university or college for examination or academic award. Any source of information from all the
sources are quoted and acknowledged accordingly. Any part of this work should not be used
without my permission or the hat of Kabarak University.
Student
Sumba Kiprop
Signature …………………………………………
REG. NO: GMP/M/0206/01/20
Date
iii
RECOMMENDATIONS
The proposal “Investigation of Photocatalytic Effect of Tantalum Doped Anodic Tin Thin
Films” has been written by Sumba Kiprop and submitted to the School of Postgraduate studies
for the degree of Master of Science in Electrical and Electronics Engineering Kabarak University
under my authorization as supervisor,
Dr. Christopher Mkirema Maghanga
Department of Biological and Physical Sciences
Kabarak University
Signature………………………………………………
Date
Prof. Maurice Mghendi Mwamburi
Department of Physics
University of Eldoret
Signature……………………………………………….
Date
iv
ACKNOWLEDGEMENTS
I want to thank God for the protection, care, and good health He favored me with since I began
this work. It has been by his grace. I appreciate my supervisors Prof. Mghendi Mwamburi and
Dr. Christopher Maghanga for their encouragement, tireless work, and time involved in doing
this work. My gratitude goes to my family for their prayers and moral support, and their financial
support.
v
DEDICATION
This work is dedicated to son, Arnold Kimutai and beloved wife Faith Kulei.
vi
Abstract
Photocatalysis is defined as the splitting of water into oxygen and hydrogen atoms in
presence of UV light where electrons in the valence band are excited to the conduction
band. Energy absorbed by the contaminants and the photocatalyst is more than or equal to
the Bandgap of the material
contaminants +photocatalysts →carbon iv oxide +water intermediates
Novel photocatalysis is an upcoming technique of treating organic pollutants in water that
tend to cause harm to the environment and also living organisms due to their high
chemical stability availability. This idea was brought about in the 20th century in
Fujishima, A., Honda, K.-I., and Kikuchi, S.-I. (1969) Photosensitized Electrolytic
Oxidation on Semiconducting n-Type TiO2 Electrode. The Journal of the Society of
Chemical Industry, Japan, 72, 108-113. http://dx.doi.org/10.1246/nikkashi1898.72.108, It
has since then improved with advancement in technology. Effluents from industries and
commercial residential estates are channeled into the wastewater system for treatment
before being released into rivers or bare land. Since the treatment involving other
techniques may not be effective due to the high chemical stability of the waste there was
a need to come up with using doped tin oxide film which has proved to be more effective
The past techniques that include water treatment using different techniques have not
resolved the matter. This necessitates the need for more affordable approaches to
managing wastewater as well as purification of water for consumption. Photocatalytic
vii
degradation of pollutants is an upcoming technology in the purification of water. This
proposal aims to use tin oxide doped with tantalum to be used in photocatalytic water
purification. The research will be experimental. Equipment to be used are hot plate,
magnetic stirrer, pestle and mortar, hydrated tin chloride, de-ionized water, ammonium
hydroxide implying that SnO will first be prepared in the laboratory using tin chloride as
initial reagent and Tantalum will be incorporated as a dopant. Thereafter fabrication will
be done on a substrate by anodization. Heat correlates to absorption capability of SnO
and subsequently doping using tantalum will increase the treatment will be done at 2500C
after fabricating the film. The optical characterization will be done using a UV-VIS NIR
spectrophotometer to obtain reflectance data which will aid in determining the optical
properties of the films. Data analysis of reflectance absorption of the film This implies
maximum absorption of the films which is a fundamental property in photocatalytic water
purification. Hence tantalum doped SnO films have good photocatalytic properties and
can be used for photocatalytic water purification.
Keywords photocatalysis, anodization, doping, semi-conductor, substrate
viii
Contents
DECLARATION ............................................................................................................................................... ii
RECOMMENDATIONS ............................................................................................................................. iii
ACKNOWLEDGEMENTS ................................................................................................................................ iv
DEDICATION............................................................................................................................................. v
Abstract ........................................................................................................................................................ vi
LIST OF ABBREVIATIONS AND ACRONYMS ................................................................................................... x
CHAPTER ONE ........................................................................................................................................... 1
INTRODUCTION ............................................................................................................................................. 1
Introduction ............................................................................................................................................... 1
Background of the study ........................................................................................................................... 1
Statement of the problem .......................................................................................................................... 3
Objectives of the study.............................................................................................................................. 4
Specific objectives: ............................................................................................................................... 4
Research Questions ................................................................................................................................... 4
Significance of the study ........................................................................................................................... 5
Justification of the study ........................................................................................................................... 5
CHAPTER TWO .......................................................................................................................................... 6
LITERATURE REVIEW ............................................................................................................................. 6
INTRODUCTION .................................................................................................................................... 6
ix
PHOTOCATALYSIS PROCESS ............................................................................................................. 6
FABRICATION TECHNIQUE ................................................................................................................ 7
CHAPTER THREE .................................................................................................................................... 10
METHODOLOGY ..................................................................................................................................... 10
Introduction ............................................................................................................................................. 10
Synthesis of SnO2 ................................................................................................................................... 10
REFERENCES ........................................................................................................................................... 11
Appendix A: Work Plan.............................................................................................................................. 13
Appendix B: Research Budget .................................................................................................................... 14
x
LIST OF ABBREVIATIONS AND ACRONYMS
Sn
Tin
TAO
Tin Anoded Oxides
SnO2
Tin Oxide
Ta
Tantalum
SEM
Scanning Electron Microscope
TEM
Transmission Electron Microscopy
XRD
Xray Diffraction
UV
Ultra Violet
NIR
Near Infrared Regions
Vis
Visible
1
CHAPTER ONE
INTRODUCTION
Introduction
This section discusses the background of sources of water pollution across the globe, adverse
effects on living organisms, and ways of mitigating the problem. It further gives the
statement of the problem, objectives of the research, research questions, hypothesis as well as
stating the assumptions to be made in the research.
Background of the study
The rise in water pollution by organic pollutants has necessitated a dynamic technique of
mitigating the problem to reduce the impact on the environment and especially living
organisms. The other methods including, pH correction, sludge drying, disinfection,
filtration, sedimentation, coagulation has not adequately worked well as some of the
techniques applied have adverse effects on the living animals in water as well as soil.
Compounds released to water bodies are often stable and difficult to degrade in wastewater
facilities thus posing a serious long-term risk.
The development of novel and efficient technologies for the environmentally sustainable
removal of these dangerous compounds from different sources is of crucial pertinence.
According to Abdulla et al.,(2017). Tin dioxide is used as a Photocatalysis for Water
Treatment, the photocatalytic oxidation of organic pollutants in the presence of a
semiconductor such as tin oxide in green technology and seems to be a highly promising
technique for water treatment and removal of intransigent compounds. The efficiency of
2
photocatalysis can be enhanced by modification of the tin oxide resulting in a lower
recombination rate of electron-hole pair and an increase in efficiency of semiconductor
during excitation state allowing degradation to proceed under visible light irradiation.
Photocatalysis is widely applied in wastewater treatment to degrade organic pollutants which
can be difficult to degrade due to their chemical stability. Its essence is to produce hydroxyl
radicals which destroy pollutants in the wastewater.
The most recent technique of treating wastewater includes applying photocatalysis like zinc
oxide which is less superior than tin oxide. Its versatility as a metal oxide is due to the
variable valence state and the existence of oxygen vacancy defects. Its stability in water
solution and sufficient negative band edge position for the proton reduction.
This study was necessitated by the impact of wastewater on the environment and which has
caused mild effects on living organisms; both human beings and animals, it was, therefore,
necessary to focus on a more effective technique that would see pollution by wastewater
brought down. More has it has been realized in urban settlements across the globe where
there is a lot of wastewater being channeled to water bodies and some to the bare land.
3
Statement of the problem
The significant increase of organic waste in the environment has necessitated an advanced
technique of treating organic waste to reduce the impact on the immediate users. Photocatalysis
is an upcoming advanced technique that has shown its superiorities over other techniques in that
it can degrade more stable organic dyes and is an affordable technique. Therefore, this research
seeks to find a more effective technique of wastewater treatment using tin oxide. Photocatalysis
occurs when the metal oxide is exposed to adequate photonic energy which causes excitation of
electrons from the valence to the conduction band and subsequently oxygen and hydrogen
molecules produced decompose the organic waste.
4
Objectives of the study
The objective of this study is to investigate the effect of tantalum doped anodic oxidized tin
thin film on pollutants.
Specific objectives:
i.
To investigate the optical and structural properties of the tin oxide film
ii.
To fabricate thin films of tin oxide film by anodization
iii.
To investigate how pigmenting the fabricated films with Tantalum at different
concentrations affect the tin oxide film.
iv.
To investigate the photocatalytic activity of tin oxide film.
Research Questions
i.
what are the optical and structural properties of the fabricated tin oxide film?
ii.
what is the photocatalytic activity of the films?
iii.
what is the best technique for the preparation of tin oxide films?
iv.
what is the effect of pigment on a fabricated film?
v.
what is the effect of a dopant(tantalum) in the film preparation using the anodization
technique?
5
Significance of the study
This technique of using a semiconductor in the presence of light has proven to be more effective
and durable and therefore there is a need to find the best semi-conductor. Tin is abundant on earth
and has an oxide that is more stable in water and has sufficient negative band edge position for the
proton reduction. Novel photocatalysis is an advanced technology. Pollution being a major
problem in developed and developing countries seeks attention to mitigate the problem. In Kenya,
wastewater is released into water bodies without being effectively treated which causes a lot of
negative effects to the environment; both plants and animals.
Justification of the study
The tin oxide will be prepared, surface treatment, film deposition technique will be analyzed;
pyrolytic spraying technique will be applied that will give a uniform coat on a substrate, thereafter
measurement of the valence band of the film, refractive index, and also impurities. Film
preparation is an essential stage that determines the properties of the film.
6
CHAPTER TWO
LITERATURE REVIEW
INTRODUCTION
This chapter discusses the photocatalysis processes, some photocatalytic materials, fabrication
techniques, Tin Oxide fabrication technique, analysis of its optical properties, advantages of the
Tin Oxide semiconductor used, the past experimental results of the material, recent trends in
photocatalysis process and materials, and the importance of the Tantalum dopant used.
Figure 1. Crystal structure of SnO
PHOTOCATALYSIS PROCESS
Photocatalysis is an upcoming technique in the disinfection of wastewater effluents and
concurrent contaminants in water for consumption. Organic components which do not degrade
7
due to their high chemical stability can be disintegrated using photocatalysis, which makes use of
solar energy and breaks down the effluents in water. Photocatalysis is defined as the acceleration
of a photoreaction in the presence of a catalyst whereas, in catalyzed photolysis, light is absorbed
in the presence of an adsorbed substrate. Primary steps in the mechanism of photocatalysis are;
Formation of charge carriers by photoabsorption Charge carriers recombine trapping of
conduction valence band electron trapping of a valence band hole.
A tin oxide semiconductor is environmentally friendly therefore making it suitable for use. SnO2
rutile crystalline structure n-type semi-conductor. Its high photoabsorption ability, non-toxicity,
and affordability give merits over other semi-conductors
FABRICATION TECHNIQUE
Fabrication techniques are either chemical or physical approaches whereby chemical is further
subdivided into; gas and liquid phases. Physical processes include evaporation, sputtering
technique while chemicals include sol-gel technique, chemical bath deposition, spray pyrolysis,
plating technique, chemical vapor techniques.
Anodization technique will be preferred over the other techniques due to its ease in maintaining
the film fabricated, it can be cleaned with water and mild detergents to restore its original luster,
8
its high UV stability, and a durable film also protects the base metal to offer a deeper richer
metallic appearance, therefore, giving high-quality architectural finish.
Figure 1: Schematic diagram for anodization method. Nemes et al., (2011)
Electrochemical Deposition technique (ECD)
This technique is considered to be the cheapest method of fabrication of thin film. ECD
represents a major technology for mass production of the large area metallic protective coatings
in the industry. The technique employs a combination of reduction and oxidation reactions of
chemical precursors electrolytes of aqueous solutions or organic solution. The other advantage is
that it includes low fabrication temperatures, high purity, ease of controlling the thickness film,
uniformity, and rate of deposition.
ECD technique can be divided into two groups namely;
9
i.
Electrolysis plating-it uses external film, a uniform source of power to drive the
electrochemical reaction that leads to deposition of a thin film onto an electrically
conductive substrate.
ii.
Electrolysis plate which does not require an external power supply but requires catalysts
to activate the surface of a specimen
10
CHAPTER THREE
METHODOLOGY
Introduction
This chapter will introduce the mode of synthesizing SnO2 which involves an experimental
approach, fabrication technique, characterization of the achieved film, and testing of the
photocatalytic activity of tin oxide. An experimental approach will be applied where the
experiment will be conducted in a laboratory.
Synthesis of SnO2
For the preparation of SnO2 appropriate amounts of 0.5 M, hydrated tin chloride will be
dissolved in de-ionized water, stirring will be done for about 2 hours by keeping it on the hot
plate with a magnetic stirrer. Ammonium hydroxide (NH4OH) drop by drop while stirring until
the formation of a white precipitate. after about 30 minutes of stirring, the mixtures are then
rinsed several times with de-ionized water to remove excess chlorides or other ionic impurities
that may have been formed during the synthesis process. Then the air drying will be done at 60 0
for about 20 hours, thereafter natural cooling will apply at room temperatures to produce the
powdered precursors which will be collected carefully. Thereafter powdered precursors will be
ground in an agate mortar -pestle for about 3o minutes to obtain the fine powders which will then
be placed in Al2O3 crucibles for sintering in a furnace and will be maintained at 120 0 for about 2
hours to obtain the annealed powder sample of tin oxide.
11
Materials
Tin chloride, SnCl2
De-ionized water
Ammonium hydroxide, NH4OH
Aluminum hydroxide, Al2O3
Hot plate
Magnetic stirrer
Pestle and mortar
X-ray diffractometer
REFERENCES
1.
2.
3.
Tin and Inorganic Tin Compounds: Concise International Chemical Assessment
Document 65, (2005), World Health Organization
S.Zumdahl (2009). Chemical Principles 6th Ed. Houghton Mifflin Company.
p. A23. ISBN 978-0-618-94690-7.
Jump up to:a b c NIOSH Pocket Guide to Chemical Hazards. "#0615". National Institute
for Occupational Safety and
12
Health (NIOSH’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’
’’’’’’’’’’’’’’’’’’’’’’’’’’’’’). USETHV
a.
Jump up to a b c d e f Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic
Chemistry, Elsevier ISBN 0-12-352651-5
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4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Satya Prakash (2000), Advanced Inorganic Chemistry: V. 1, S.
Chand, ISBN 81-219-0263-0
Arthur Sutcliffe (1930) Practical Chemistry for Advanced Students (1949 Ed.), John
Murray - London.
Braun, Rolf Michael; Hoppe, Rudolf (1978). "The First Oxostannate(II):
K2Sn2O3". Angewandte Chemie International Edition in English. 17 (6): 449–
450. doi:10.1002/anie.197804491.
R. M Braun ,R. Hoppe,(1982). "Über Oxostannate(II). III. K2Sn2O3, Rb2Sn2O3 und
Cs2Sn2O3 - ein Vergleich". Zeitschrift für Anorganische und Allgemeine Chemie. 485:
15–22. doi:10.1002/zaac.19824850103.
R M Braun R Hoppe Z. Naturforsch. (1982), 37B, 688-694
T. Bring, T.; Jonson, B.; Kloo, L.; Rosdahl, J; Wallenberg, R. (2007), "Colour
development in copper ruby alkali silicate glasses. Part I: The impact of tin oxide, time
and temperature", Glass Technology, Eur. J. Glass Science & Technology, Part A, 48 (2):
101–108, ISSN 1753-3546
S.O. Kuchevev, T.P. Baumann ,P.A Sterne .Y.M , Wang, T.V .Buuren and A.V
.Hamza:Surface electronic states in 3D SnO2 nanostructures.Physics.Rev.B.72
035404(2005)
M.M.Bagheri.Mohagheghi and M.S.Saremi. The influence of Al doping on the
electrical.Optical and structural properties of SnO2 transparent conducting films
deposited by the spray pyrolysis technique.” S.phys.D:Appl .37,1248 (2004)
A,Dodd,A.Makinley, M.Sounders of nanocrystalline SnO2 -ZnO, Photocatysts.”
Nanotechnology 17,692 (2006)
Y.C.O, Y.Li, DiJia solid-state synthesis of SnO2-graphene nanocomposite fir
photocatalysis and formaldehyde gas sensing RSC Adv .4,461179 (2004)
G.S Korotchenkov, S.V Dmitriev, V.L Brynari, Process Development for low-cost
power-consuming SnO2 thin film gas sensors (TFGS). Sensors and actuators B54 202
(1999)
13
Appendix A: Work Plan
Month
Activity
Concept and
proposal writing
and submission
Proposal
Presentation and
amendments
Conducting
laboratory
experimental
work
Analysis of the
results and
discussion of the
findings
MayAug
2021
SeptDec
2021
Jan-Mar
Apr-June
Jul-Aug
Sept-Dec
2022
2022
2022
2022
14
Thesis writing
and presentation
Thesis
amendments and
graduation
Appendix B: Research Budget
Quantity
Activity/Item
Unit price (Kshs) Totals
1pc
Computer
45,000
Internet access services
45,000
20,000
Subtotal
65,000
Printing expenses
1
i. Research materials
10,000
8 copies
ii. Proposal
1,000
8,000
10 copies
iii. Thesis
2,000
20,000
15
38,000
Subtotal
Support services
Transport expenses
80,000
Conference presentations
4 conferences
I. Registration
5,000
20,000
ii.Travelling
10,000
40,000
iii.Accomodation
15,000
45,000
Subtotals
85,000
Stationaries
1pc
i.16 GB Flash drive
2,000
2,000
5pcs
Writing materials
200
1,000
5pcs
Files and Folders
200
1,000
Subtotals
45,000
Grand Totals
313,000
16