1. The document introduces a course on the principle and application of photocatalysis. 2. Photocatalysis uses solar energy to promote chemical reactions for energy conversion and environmental purification without changing the photocatalyst. 3. Semiconductor materials like TiO2 can be used as photocatalysts by generating electron-hole pairs when irradiated by light which then trigger redox reactions to degrade pollutants.

1. The Principle and Application
of Photocatalysis
Teacher: Dr. Xin Yan
E-mail: xinyan@chd.edu.cn

2. 西安
Xi’an
• Chang’an University, or CHD, is a national key
university. Located in Xi’an City, Shaanxi
Province, CHD has two campuses and three
training bases, with a total area of 250 hectares.

3. A Video Introduction to Xi’an

4. Gate Rainbow Girl
Library

5. Classroom building
Student canteen
Stadium

6. Course Information

7. Brief introduction of Course
Course name
The principle and application of photocatalysis
Course Type
Specialized and basic course for postgraduate students
Credits: 2
Teaching Hours: 32 hours (2 hours every week)
Exam method
Presentation and assignments （paper reports）

8. The basic knowledge and principles of photocatalytic
reaction are described in a comprehensive and systematic way.
The research progress and achievements of the design,
preparation and modification of photocatalyst are introduced.
The research methods of the physicochemical properties of
photocatalytic materials, the evaluation methods of
photocatalytic activity are summarized. The applications of
hydrogen, self-cleaning and organic matter conversion were
introduced in depth.

9. Through the study of this course, students can
master the basic theory and concept of photocatalytic
materials, learn how to analyze and solve the design of
materials, establish the basic scientific way of thinking,
and cultivate students' ability to use theoretical
knowledge and engage in scientific practice.

10. Students should master
the basic principles of photocatalytic materials and be familiar with the
photocatalytic reaction mechanism.
the research methods of physical and chemical properties of photocatalytic
materials and the evaluation methods of photocatalytic activity
understand the application of photocatalytic materials in environmental
purification, hydrogen production from water, self-cleaning and organic matter
conversion, etc.
 train students to analyze the problems existing in photocatalytic materials and
have the ability to design high-performance photocatalytic materials.

12. 1. Introduction to photocatalysis
2. TiO2 Nanomaterials a Future Prospect
3. TiO2-High Surface Area Materials Based Composite
Photocatalytic Nanomaterials for Degradation of pollutants:
A Review
4. Preparation, Characterization and Applications of Visible
Light Responsive Photocatalytic Materials
5. Silver Phosphate（Ag3PO4） Based Photocatalysis: A Brief
Review from Fundamentals to Applications

13. 1.Introduction to photocatalysis

14. 6%
2%
17%
75%
Energy problems
10%
24%
40%
26%
CxHy + O2 H2O + CO2 + SO2 + NOx
coal oil
Natural
gas
etc
In China
In the world
煤
其他
the situation of energy mix and consumption
Unsustainable, Pollute the environment
oil
coal
Natural gas
etc

15. Air Pollution map
pm2.5：http://aqicn.org/map/world/cn/
Environment problems

16. Environment problems
Smoke and dust in Power Plant (England) Photochemical smog in Los Angeles (USA)
Acid Rain Pollution Sandstorm

17. Water pollution problems
Dye wastewater heavy metal pollution
Antibiotic pollution

18. Photocatalytic technique
Photocatalysis: Using solar energy for energy conversion and environmental
purification technology
Energy photocatalysis Environmental photocatalytsis

19. What is photocatalysis
Photocatalyst is a substance that can promote chemical reaction
without changing itself under the irradiation of
light. Photocatalytic reactions can promote the synthesis or
degradation of compounds . Photocatalytic reactions can convert
light energy into chemical reactions to produce catalysis.

20. Conduction band
valence band
Conduction band
Conduction band
valence band valence band
Band gap
Band gap
Conductor Semi-Conductor Insulator
Which material can be used as a
photocatalyst?

21. In a semiconductor, electrons was excitated from the valence band under light
irradiation. So photo generated electrons are formed in the conduction band and
photo generated holes are formed in the valence band. Photo generated electrons
have strong reducibility and can react with oxygen to obtain superoxide radicals.
Photo generated holes react with hydroxide ions to obtain hydroxyl radicals.
These are strong oxidizing free radicals that can degrade organic pollutants.

22. Question 1:
What can we do with photocatalysis?
Question 2:
What kind of enegry does photocatalysis use?
Question 3:
Which materials can be used as photocatalyst?

23. Influence factors of photocatalytic
reaction process
1.The absorption efficiency of light
How to improve the absorption
efficiency of light?

24. Nanomaterials
Porous materials
improve the absorption efficiency of light
Bulk material
0 D
1 D
2 D
Transmission electron microscope
Scanning electron microscope

25. Eg=3.2 eV
Eg=2.7 eV
CB
VB
CB
VB
Eg=2.7 eV
CB
VB
UV light
Visible light
Visible light
Non-metal doped
Metal doped
Improved light absorption efficiency by ion doping

26. Improved light absorption efficiency by surface modification

27. Improve the separation efficiency of
hole electrons
Surface modification by noble metal

28. Surface modification by carbon nanotube

29. Semiconductor heterojunction

30. Different type of heterojunction
Key Point
Relative position of the conduction band and valence band
Recombination

31. Development of new visible light photocatalysts
Ag3PO4
Methyl
orange
Rhodamine B

32. graphite phase carbon nitride (g-C3N4)
 non-metallic material
 narrow band gap width (Eg = 2.70 eV)
 good chemical stability
 simple preparation method

33. Photocatalytic application
Photocatalytic
application
National defense and military
Medical care and public health

34. Water treatment

35. Photocatalytic hydrogen production
cycle

36. Air cleaning
Ammonia
Formaldehyde
benzene

37. Inactivate cancer cells
Nano titanium dioxide was injected into the cancerous sites of mice
Before the light irradiation After the light irradiation
TiO2

38. Under UV light, water is completely
infiltrated on the titanium oxide
film. Therefore, coating a layer of titanium
oxide on the surface of bathroom mirror, car
glass and rearview mirror can play a role in
preventing fogging.
Application of anti-fogging and self-
cleaning coatings

39. TiO2 thin
films
Organic dirt
Inorganic dirt
CO2 H2O
Surface self-cleaning
National Grand Theatre
(in Beijing)

40. Conclusion
Environmental problems and the energy crisis have created great challenges for scientist and
technologist at a global level. For the last 3-4 decades, major attention has been given for
photocatalysis to overcome these problems.
Photocatalysis is an effective catalytic process with potential applications in solving above
mentioned problems by degrading pollutants, reducing CO2 levels and water splitting,
respectively.
Till today, various photocatalytic materials, photocatalytic reactor, degradation of various
organic compound present in air and water have been studied and demonstrated. In spite of
significant research work carried out in the field of photocatalysis, there are several challenges
needing to be addressed such as enhancement in photocatalytic activity, development of
visible light activated photocatalysts, search of alternative photocatalytic materials, design and
development of photocatalytic reactors based on the irradiation source.