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Semiconductor Nanoparticle/Molecular Catalyst Hybrids
for Solar Fuel Conversion
Noah Henke, Alex Wood, Carissa Zibolsky, Allison Opheim, Ashley Garb
Advisor: Jodie Garb
Mentor: Jier Huang, Ph.D., Physical and Materials Chemistry, Marquette University
Research: Semiconductor Nanoparticles/Molecular Catalyst Hybrid
Abstract
The development of clean and renewable energy is critical to partially address the energy
crisis and climate issues. Inspired by nature, artificial photosynthesis through water
splitting by solar energy conversion is one of the most attractive approaches for the
development. The overall water splitting includes two half-catalytic reactions, i.e. hydrogen
(HER) and oxygen (OER) evolution reactions. An efficient catalyst coupling with a
photosensitizer is required to perform each of these catalytic reactions. The objective of
this research program is to develop hybrid materials that integrate emerging earthabundant molecular catalysts with semiconductor nanoparticle photosensitizers. Dr.
Huang’s lab is interested in the molecular catalysts that mimic the function of [FeFe]
hydrogenase, including [FeFe] hydrogenase, cobaloxime, and Dubois’ nickel catalysts
(Figure 1), because they are among the most effective synthetic transition metal complexes
known for HER. The Laconia SMART (Students Modeling A Research Topic) Team used 3D
printing technology to model the active site of [FeFe] hydrogenase and understand its
catalytic function for HER. [FeFe] hydrogenase is an enzyme that catalyzes proton
reduction to bind hydrogen together. Arg265, Lys288, and Lys409 are positively charged
residues that line the channel entrance. Lys 188 is at the end of the channel and may help
to orient the 2Fe subcluster during hydrogen insertion. The fundamental understanding of
the catalytic function of the [FeFe] hydrogenase active site in HER will provide insight into
the rational design of efficient catalysts for solar fuel generation.
Cl
NH
N
Fe4S4
cys
OC
S S
SH
NC
H
Fe
Fe
OC
S
NC
1
CO
Fe
Fe
CN OC
CO
CO
S
H O
N
O
NH
CN
P
N
N
O
H
R
R
2
P
N(CH3)2
COOH, PO3H
3
e-
Catalyst
hυ
P680
hυ
R
The synthesis of [FeFe] hydrogenase model complex functionalized with –
COOH group
O
Alpha Carbon Backbone is colored white.
Alpha helices are colored orchid.
Beta sheets are colored aqua.
Iron is colored yellow.
Hydrogen bonds are colored honey dew.
O
O
P700
O
H 2O 2
Br
Br
O
O
• The hybrid materials that integrate CdSe quantum dots as
photosensitizers and [FeFe] hydrogenase as molecular catalysts have
been developed
• The Laconia High school team have successfully used 3D printing
technology and modeled [FeFe] hydrogenase active site
• The future work will test H2 generation efficiency by illuminating the
prepared hybrid materials with visible light that mimic sunlight.
Br
Br
O
O
O
O
Fe3(CO)12
Na2S2
toluene, reflux, 4h
Br
S
S S
S
(OC)3Fe
2H+ or CO2
Summary and Future Work
O
CrO3
NBS
Br
e
P700*
4H++O2
Figure 5. The absorption spectra of CdSe quantum dots
with different sizes
Active site amino acids displayed in deep pink.
Arg 275
Lys 288
Lys 409
Lys 188
4
Fossil fuels create CO2 which may be detrimental to the environment. Decreasing fossil fuel
usage would also improve the environmental aspect of our lives, and provide renewable
energy for generations to come. Because fossil fuels are limited and create hazardous
byproducts such as high levels of CO2, a need for renewable resources such as sunlight to
provide energy is necessary. According to the Journal of the Royal Society, the sun provides
enough energy in one hour to power our entire world for a year. The ability to mimic
natural photosynthesis is currently being researched as an alternative. In artificial
photosynthesis the photocathode works in a similar way as Photosystem I creating H2 with
the help of a catalyst, such as [FeFe] Hydrogenase.
H2 O
10min
700
Ph
R=PO3H, SH, COOH etc.
Comparing Natural and Artificial Photosynthesis
e-
5min
500 550 600 650
Wavelength (nm)
450
Ph
Figure 1. Active site of [FeFe] hydrogenase (1), [FeFe] hydrogenase model complex (2), cobaloxime (3), and Dubois Ni catalyst
(4).
e
P680*
Absorbance (a.u.)
N
P
3min
Figure 4. CdSe quantum dots with different sizes result in
different colors
P
Ni
2min
400
R=H, COOCH3,
N
CO
1min
N
Ph
Ph
[FeFe] hydrogenase is currently being studied for its ability to turn
sunlight into hydrogen. [FeFe] hydrogenase is an enzyme that catalyzes
proton reduction to form hydrogen. [FeFe] hydrogenase is modeled
using PDB file 3LX4.
CdSe quantum dots
R
N
Co
N
O
R
In the initial studies:
• CdSe quantum dots with different sizes were prepared and used as photosensitizers
•[FeFe] hydrogenase model complex functionalized with –COOH group were synthesized
•The hybrid catalysts were obtained after [FeFe] hydronase model complex was attached to CdSe
nanoparticle surface with –COOH group.
FeFe Hydrogenase Model
Fe(CO)3
H2 or
HCOOH,
CH3OH etc.
Acknowledgements
Photosystem I
-
Photosystem II
Figure 2. Natural Photosynthesis
HO
•
•
•
•
+
CdSe
OO
OH
NIH-CTSA
MSOE (Milwaukee School of Engineering)
Marquette University
Laconia High School SMART Team
2e2e-
2e2H++1/2O2
H2
HEC PS
PS WOC
2ePhotoanode
H2O
H+
2H+
2e-
H2
PS = photosensitizer
HEC = hydrogen evolution catalyst
WOC = water oxidation catalyst
Photocathode
Figure 6. CdSe quantumdots
Illumination with l > 400 nm
H+ source: triethylamine hydrochloride
Sacrificial donor: triethanolamine
S
OC
OC Fe
OC
S
CO
Fe CO
CO
2H+
Figure 3. Artificial Photosynthesis (light-driven water splitting cell)
“The SMART Team Program is supported by the National Center for Advancing Translational Sciences, National Institutes of Health, through Grant Number 8UL1TR000055. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH.”