20130418 BO Sapporo.ppt [互換モード]

Microsoft PowerPoint - 20130418_BO_Sapporo.ppt []2013/04/18
Advanced Course in Photocatalytic Reaction Chemistry
understanding chemistry by understanding photocatalysis understanding photocatalysis by understanding chemistry
Division of Environmental Material Science, Graduate School of Environmental Science The first semester of Fiscal 2013 08:4510:15, Thursday at Lecture Room D103
Bunsho Ohtani, Ewa Kowalska and Mai Takase
Catalysis Research Center, Hokkaido University, Sapporo 001-0021, Japan 011-706-9132 (dial-in)/011-706-9133 (facsimile)
[email protected] http://www.hucc.hokudai.ac.jp/~k15391/
objectives/goal/keywords
<< objectives >> Understanding the mechanism of decomposition of pollutants, methods of photocatalysts preparation, design of practical photocatalytic reaction systems, and strategy for enhancement of photocatalytic activity.
<< goal >> To understand principle of photocatalytic reaction from the standpoint of chemistry and strategy for practical applications. To obtain scientific method for research on functional solid materials.
<< keywords >> Photocatalyst, Photoinduced oxidative decomposition, Superhydro- philicity, Excited electron-positive hole, Structure-activity correlation, Higher photocatalytic activity, Visible-light response
2013/04/18—Advanced Course in Photocatalytic Reaction Chemistry 4
schedule
(1) April 11 introduction of photocatalysis (2) April 18 interaction between substances and light (3) April 25 electronic structure and photoabsorption (4) May 2 thermodynamics: electron and positive hole (5) May 9 adsorption (6) May 16 (Professor Ewa Kowalska) (7) May 23 kinetic analysis of photocatalysis (8) May 30 kinetics and photocatalytic activity (1)
June 6 (no class = class for Monday) (9) June 13 kinetics and photocatalytic activity (2) (10) June 20 kinetics and action spectrum analysis (1) (11) June 27 (Professor Mai Takase) (12) July 4 action spectrum analysis (2) and crystal
structure of photocatalysts (13) July 11 design and development of photocatalysts (1) (14) July 18 design and development of photocatalysts (2) (15) July 25 design and development of photocatalysts (3)
August 1
comments on this lecture
Please send email in Japanese or English within 48 hours
to: [email protected] subject: pc2013MMDD-XXXXXXXX body: (full name) (nickname) (comments and/or questions on today's lecture)
photocatalysis industries in Japan 2010(2009): ca. 350 million USD [440 million USD for 2009]
45(47)%
practical applications
Q What is the general chemical reaction(s) included in the practical applications of photocatalysis?
(1) Photocatalysts such as titanium(IV) oxide coated or fixed on the solid materials adsorb organic compounds from water or air.
(2) The adsorbed organic compounds are completely decomposed into carbon dioxide (mineralization).
(3) The surface of photocatalytic coatings becomes superhydrophilic.
point 1: Molecular oxygen (O2) in air leads to mineralization point 2: Reduction as a counterpart of oxidation is for O2. point 3: Intermediate species from O2 are known to act as oxidants. point 4: In the absence of O2, other reduction reactions may proceed.
mechanism
photocatalysis: two major phenomena
photocatalytic oxidation: organic and inorganic compounds are oxidized under air to be inorganic materials, i.e, mineralization.
left: photocatalytic/right: ordinaryleft: photocatalytic/right: ordinary
mechanism
principle of photocatalytic reaction
e-
e-
h+
h+
2) relaxation 3a) reduction & oxidation 3b) recombination
1) photoexcitation = electron and hole
2) relaxation 3a) reduction & oxidation 3b) recombination
catalysis and photocatalysis
• Catalysis and photocatalysis should be thought different. • There are many common methods for characterization
catalysis
photoexcitation
photocatalysis • vibrational (infrared): water warmed by sunlight • rotational (microwave): microwave oven
the easiest way for making excited states:
photoabsorption
what is electromagnetic wave
Light is electromagnetic wave. Which are electromagnetic waves? alpha beam, beta beam, gamma beam, X ray, ultraviolet light, visible light, infrared light, microwave, radio wave, electron beam

what is electromagnetic wave
Light is electromagnetic wave. Which are electromagnetic waves? alpha beam, beta beam, gamma beam, X ray, ultraviolet light, visible light, infrared light, microwave, radio wave, electron beam

Q: speed of light
• The shorter the wavelength, the higher the energy.
• The speed of light is constant in vacuum, not depending on its wavelength:
• number of vibration per unit time = frequency (Hz)
• wavelength x frequency = (speed of light)
• (speed of light)/wavelength = frequency
Q: speed of light
• The shorter the wavelength, the higher the energy.
• The speed of light is constant in vacuum, not depending on its wavelength:
ca. 3 x 108 m s-1
• number of vibration per unit time = frequency (Hz)
• wavelength x frequency = (speed of light)
• (speed of light)/wavelength = frequency
light: wave and particle
• no weight • electron: particle and wave at the same time with weight
energy of light
• Even if the total energy is the same, the effect of light may different depending on the energy of each photon.
Q: boundary of ultraviolet and visible light
various electromagnetic wave
Q: Answer the boundary wavelength of ultraviolet and visible light.
8
7
5
2
-1
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
6
4
3
1
0
-2
dm
mm
μm
nm

pm
km
m
cm
Q: boundary of ultraviolet and visible light
various electromagnetic wave
Q: Answer the boundary wavelength of ultraviolet and visible light.
8
7
5
2
-1
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
6
4
3
1
0
-2
dm
mm
μm
nm

pm
km
m
cm
boundary of ultraviolet and visible light
• "Visible" means one can see the light. • The wavelength of light sensible is different individually. • Ordinary speaking, it is approximately 400 nm, certain
people can be sensible for the light of wavelength shorter than 380 nm
Q: Why leaves look green?
interaction of light and substances the three primary colors: red, green and
blue Think complimentary color(s).
Q: Why leaves look green?
interaction of light and substances the three primary colors: red, green and
blue Think complimentary color(s).
(1) Solar radiation contain all light of colors (white).
(2) Chlorophyll in leaves absorbs the light of red and blue (blue-violet).
(3) Remaining green light is reflected to make leaves look green.
light and shadow
Q: Draw photoabsorption spectrum of chlorophyll. • electronic absorption spectrum = UV-Vis: extent of photoabsorption is
plotted against wavelength • hint: wavelengths of red and blue lights are 650 nm and 450 nm.
Q: Draw photoabsorption spectrum of chlorophyll. • electronic absorption spectrum = UV-Vis: extent of photoabsorption is
plotted against wavelength • hint: wavelengths of red and blue lights are 650 nm and 450 nm.
interaction between light and substance
• electronic/vibrational/rotational energies are "quantized", i.e. discrete level of energy
• energy gap: energy difference between the levels • Only light of energy which is the same as energy gap is absorbed. • photoabsorption = excited state • Excited state must release the energy to go back to ground state.
electronic energy
atom as a fundamental particle of substance positively charged nuclei negatively charged electrons electrostatic interaction between them electron: wave and particle at the same time quantum theory to interpret both discrete energy level = quantization
vibrational energy
molecule: assembly of atoms chemical bond: electron(s) existing between nucleus "Spring" is assumed for chemical bonds.
quantized
rotational and translational energies
molecular rotation Molecules can be rotated if they have dipole moment than changes by rotational motion. Relating to heating in a microwave oven quantized
translational energy motion of molecules themselves not quantized = continuous
photoabsorption = excitation
excited state: first, second, third ...
difference in energy = energy gap
excitation = supplying energy to excite
Heat (energy) is too small to excite.
Photons have enough energy for various modes of excitation.
comments on this lecture
Please send email in Japanese or English within 48 hours
to: [email protected] subject: pc20130418-XXXXXXXX body:
full name nickname comments (questions) on this lecture order of book(s) if any JPY1,200 (77%) JPY3,500 (79%)
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20130418 BO Sapporo.ppt [互換モード]

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