Production of Hydrogen Using Tit i B d Ph t tl t Titania Based Photocatalysts Wonyong Choi School of Environmental Science and Engineering D f Ch i lE i i Dept. of Chemical Engineering Pohang University of Science and Technology (POSTECH) Pohang, KOREA
28
Embed
Production of Hydrogen Using Tit i B d Ph t t l tTitania Based Photocatalysts … · 2014-11-11 · Production of Hydrogen Using Tit i B d Ph t t l tTitania Based Photocatalysts Wonyong
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Production of Hydrogen Using Tit i B d Ph t t l tTitania Based Photocatalysts
Wonyong Choi
School of Environmental Science and Engineering
D f Ch i l E i iDept. of Chemical Engineering
Pohang University of Science and Technology (POSTECH)
Pohang, KOREA
Solar Energy Based Hydrogen EconomySolar Energy Based Hydrogen Economy
H2 production
CO2-free CO2-neutralCO2-producing
Electrolysis(alkaline, PEM
PhotoelectrolysisPhotocatalysis
(PEC semiconductor
Thermo-chemical Natural Oil Coal
Thermo-chemical
Biological process
H2 from fossil fuelsWater splitting H2 from biomass
Wind
( ,electrolyzer)
(PEC, semiconductorpowder/colloid)
cycles(S-I cycle, etc)
PV+ Storage of l i i
High-T electrolysis
Solarth l
Nuclearth l
Natural gas
Oil Coal
Gasification
Steam
process(gasification,
pyrolysis, reforming)
process(anaerobic digestion,
fermentation)
+
Wind+EL
Proven technology but costly
PV+EL
electricity as H2
electrolysis(solar,
nuclear)
thermal thermal reforming/ water gas
shiftCO2 H2
but costly process
H2 CO2+Current
Ideal solar-to-hydrogen conversion process but far from
i l
Current industrial process
C & Scommercial realization
Capture & Storage(CCS)
Solar EnergySolar Energy
51.2 x 105 TW(10,000 x Current world demands)
• Abundant
• Environment-friendly energy source
• Safe and Clean Earth
~ 0.1% of the Earth’s surface
f
(5 times as big as South Korea)+
10% i ffi iGlobal need
13 TW ~ 10% conversion efficiency13 TW
Photocatalysis as a mean of solar energy conversion
A/A-
H O/H
e-
e-
H2O/H2
ΔG0(H O H + 1/2O )hν
ΔG0(H2O → H2 + 1/2O2)=56.7 kcal/mol
H2O/O2
D/D+
e-e-
Photocatalyst(usually semiconductors)
Water Splitting on a Photocatalyst Particle
1. Photon absorptionGeneration of e- and h+
with sufficient potentials for3. Reductionfor H2 evolution
Fullerol/TiO2 Charge Transfer Mediated Visible Light Photocatalysis
Fullerol (C60(OH)x) C60(OH)x / TiO2
g t otocata ys s
-O
O-
( 60( )x) 60( )x / 2
O-
O
O
-O
-OOH
HH TiO
OO
-O
O
O
O
O-
H
H
H
H
TiO2
C60
O-
O--O
Surface-Complex Formation
Water Soluble !- Polyhydroxylate water-soluble form of the fullerene
C60
p
Ligand(C60) to Metal (Ti) charge transfer(LMCT)
60
-C60(OH)x(ONa)y (x+y=24) y generally around 10-15Visible light activity
Theoretical Calculation of Fullerol/TiO2 Complex<Fullerol/TiO ><Fullerol + TiO > <Fullerol/TiO2><Fullerol + TiO2>
Charge TransferTransition
LUMO
Transition
hν
HOMO
•These absorption spectra are calculated using intermediate neglect of differential overlap (INDO) model parameterized for spectroscopy at the configuration interaction (CI) level of theory (ZINDO/S-CIS)
Photocatalytic Activity of Fullerol/TiOFullerol/TiO2
Dye-sensitized TiO2 nanoparticles can be modified in various ways for Dye sensitized TiO2 nanoparticles can be modified in various ways for H2 production.
The hydrogen production on dye-sensitized TiO2 is critically y g p y O2 yinfluenced by the kind of surface anchoring groups of the dye.
Nafion-coated TiO2 can anchor non-derivatized ruthenium bipyridyl 2 py ycomplexes via ion exchange for efficient hydrogen production.
The presence of alumina overcoat on TiO2 enhanced the efficiency of p 2 ydye-sensitization for hydrogen production.