SPPVersion9Final

By:
Dave Jacob
Matthias Miller
Randy Swartz

 Objectives
 Introduction
 Hydrogen Today
 Current Production Techniques
 What is Photoelectrolysis?
 Benefits
 Problems
 Experimental Methods
 Results
 Conclusion
3

 Develop effective photosensitive metal
oxides to increase the efficiency of
hydrogen production through
photoelectrolysis
 Reproduce results and refine procedures
developed by other research groups
 Lay groundwork for future research in
this field at JMU
4

 Hydrogen:
 Quick Facts
 Current State
 Conventional Methods
 Steam Methane Reforming
○ Problems
 Electrolysis
 Photoelectrolysis
 What is it?
 Benefits
5

 Hydrogen may have a future as an ideal
energy carrier
 Hydrogen has the highest energy density
per unit weight
 Significant infrastructure barriers are
currently keeping hydrogen technology
from mainstream use
6

 There are two main ways that hydrogen is
made today
 Steam Reformed Methane (SRM)
 Electrolysis
7

 STEP 1: Methane reacts
with the steam to produce
a synthesis gas made up
of hydrogen and carbon
monoxide
 STEP 2: the carbon
monoxide reacts with the
steam over a catalyst to
form hydrogen and carbon
dioxide 8

 Carbon dioxide and small amounts of
carbon monoxide and hydrogen sulfide
are byproducts of the process
 Current technologies that use hydrogen
cannot handle the impurities in the
resulting products
 Further purification (both in feedstock
and product) is required – increasing
costs
2224 42 HCOOHCH 
9

 Uses direct current to separate hydrogen
atoms from the oxygen atoms in water
 The oxygen-containing anion migrates to the
anode (+) and the hydrogen cation migrates to
the cathode (-)
 Hydrogen gas is generated at the cathode and
separated from the oxygen gas generated at
the anode
 Typical electrolyte used is Potassium
Hydroxide
10

 Anodes and cathodes
alternatively spaced in
a tank filled with 20-
30% of an electrolyte
 The electrodes are
connected in parallel
 Advantages: easy to
repair and easy to
manufacture
11

 In the U.S. 95% of all hydrogen produced comes
from Methane
 Therefore, CO2 is still being released to the
atmosphere
 Hydrogen produced from standard electrolysis
utilizes electricity from the grid, which is
predominately derived from fossil fuels
 Fossil fuels provided 71% of electricity across all
sectors in 2008
 Of the electricity from fossil fuels, 68% was from coal
 Photoelectrolysis has the potential to offer entirely
emission-free energy
12

 Same idea as normal electrolysis, but supplied
current is directly created by absorption of
sunlight by photosensitive semiconductors
 Types of Photoelectrolysis:
 Photovoltaic
 Photovoltaic/Semiconductor Liquid Junction
 Semiconductor-Liquid Junction
13

Figure shows electrolysis done with electricity directly from a PV unit. Source: Currao, 2007
14

Figure shows electrolysis using electricity from PV unit and a photosensitive anode. Source: Currao, 2007

Figure shows electrolysis done with electricity directly from photosensitive anodes. Source: Currao, 2007

 Low efficiency (typically <1%, highest
around 12%)
 Requires a bias voltage to produce viable
amounts of hydrogen
 Practicality
 High cost
 Still in experimental phase
 Scalability issues
17

1. Materials Preparation
2. Anodic Oxidation
 O-Ring Fixture
3. SEM Pictures
4. Alpha-Step
5. Annealing
6. Electrode Preparation
7. Photoelectrolysis Testing
18

 Cut 0.7 mm thick titanium sheet into 20 mm by
20 mm pieces
 Remove burrs
 Hand-grind with wet-dry silicon carbide
abrasive paper, (240-grit to 1000-grit), washing
the sample in between grit changes
 Polished in Leco VP-160 grinder/polisher with
diamond paste; cleaned, then polished again
with colloidal silica, then final cleaned
19

 To make our
electrodes, metal was
anodized in an
electrolyte with an
applied voltage
 An electrolyte is
needed instead of pure
water to produce
nanostructured oxides
at reasonable rates
Anodization of a sample in our laboratory
20

 The anodization reaction:
describes the creation of the titanium oxide film

 eHTiOOHTi 22 22
22

 The anodization reaction:
describes the creation of the tungsten trioxide

 eHWOOHW 63262 23
23

 Tungsten used was too thin for anodization in
some electrolytes; electrolyte would dissolve
holes through the tungsten from each side
 A fixture was designed and fabricated that
exposes only one side of the tungsten foil to
the electrolyte
24

Summary of Anodization Statistics
Type Sample Time (mins) Voltage (V) Electrolyte
Titanium Oxide
021 90
55 NH4F
022*
100
90
023
90024
025
Tungsten Oxide
013 - 85 1M H2SO4
015 60 50 1M H2SO4 (0.5% NaF)
017 210 20 1.5M HNO3
007 65 60 NaF
26
* Sample “020” was stripped and re-anodized and labeled sample “022”

 Once samples had been created, they
were examined on a scanning electron
microscope to see what nanostructures
were present
 Three possible nanostructures:
 Nanopores
 Nanotubes
 Nanoplatelets
27

 First structure we were able to develop
through anodization before we refined our
process
 Both metal oxides tested (as well as
several others) are capable of forming
nanoporous structures
28

 Titanium dioxide has the potential to
organize in structures called nanotubes
 The openings in these hexagonally-
arranged tubes are wider at the top and
narrow as depth increases
 These tubes are desirable features
because they increase the surface area
of the photoactive material
32

 One of the possible structures that can form
when anodizing tungsten
 Called platelets because the film consists of
randomly arranged flat rectangular shapes
 Desirable because they reflect and trap light
increasing the efficiency of the semi-
conductor film
37

 Surface profiler
used to measure
film thickness
and surface
roughness
 Highly-sensitive
stylus moves
across testing
surface
41

 TiO2 samples had nanostructure film
thicknesses ranging from 9.5 to 12 μm
 The tungsten foil was not completely flat
 Prevented the stylus of the Alpha Step
from giving an accurate reading
 Stylus actually gouges the WO3 film
 WO3 samples had nanostructure film
thicknesses of approximately 0.9 μm
42

 Nanostructures must
be crystalline to
function as a
photosensitive
electrode
 Heating of samples
allows atoms to
rearrange in the
appropriate
crystalline lattice
structure
Type
Sample
#
Annealing
Time (hrs)
Temperature
(°C)
Gas
Titanium
Oxide
021 3 500 O2
022*
STRIPPED, REGROWN
3 500
O2
023
3%
H2/N2
024
3%
H2/N2
025 O2
Tungsten
Oxide
013
3 400 O2
015
017
007
43

 A wire must be attached to allow a current
to run through sample
 A small area is scraped down to bare metal,
and a wire attached with electrically conductive
silver epoxy
 Baked in Isotemp Vacuum Oven for 1 hour
from 78°F-80°F
 To define the test area, the entire sample was
covered with electrically-insulating epoxy
(except for test area)
45

 An example of a sample
that is ready for testing
 The surface area meant
for testing can be seen
 Epoxy covers the rest of
the sample
47

 Testing of each electrode ran for 120 seconds
 Light from Mercury Vapor lamp was alternately
blocked and unblocked for 20 second intervals
 Voltage and current measured to see if electrode
was light sensitive
48

A sample being tested with incoming light source in our laboratory 49

-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0 20 40 60 80 100 120
Voltage(V)
Time (sec)
TiO2-025 Photovoltage
52

-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0 20 40 60 80 100 120
Current(mA)
Time (sec)
TiO2-025 Photocurrent Zero
Bias
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 20 40 60 80 100 120
Current(mA)
Time (sec)
TiO2-025 Photocurrent 1V
Bias
53

-0.59
-0.589
-0.588
-0.587
-0.586
-0.585
-0.584
0 20 40 60 80 100 120
Voltage(V)
Time (sec)
WO3-007 Photovoltage
An SEM image of sample WO3-007
54
* Note: each time the sample was
blocked, the plot moves closer to zero

-0.02
0
0.02
0.04
0.06
0.08
0.1
0 20 40 60 80 100 120
Current(mA)
Time (sec)
WO3-007 Photocurrent Zero
Bias
-0.2
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Current(mA)
Time (sec)
WO3-007 Photocurrent 1V
Bias
55

 We succeeded for the first time at JMU in
producing a variety of nanostructures in TiO2
and WO3 (nanopores, nanotubes,
nanoplatelets)
 Hydrogen and oxygen were produced
 The TiO2 nanotubes produced a small current
without any voltage applied
 For TiO2, nanotubes proved to be the best of
the three nanostructures
 The WO3 samples produced similar results
56

 The amount of hydrogen produced can be
predicted from the measured current flow
 If a current of 1 mA flows for 1 hour, we
expect to generate 0.42 mL of hydrogen
57

 Design test fixture/rig that would allow capture
of generated hydrogen and oxygen
 Quantify amounts of hydrogen and oxygen
produced
 Develop materials that will produce larger
photocurrents with smaller or no applied
voltage
 Develop P-type materials for photocathodes
58

 Propose practical
photoanode
architectures
 Efficiency gains will
hopefully allow for
commercialization
59
Proposed Integrated PV cell
and Photoanode setup

We would like to thank:
 Our Advisor, Dr. David J. Lawrence
 JMU Machinist Mark Starnes
 Drs. Gopal Mor & Craig Grimes from Penn State
 CISAT Mini-Grant
 Family
 Friends
Without whom this project would not have been
possible
60

Mor, G., Varghese, O., Paulose, M., Mukherjee, N., & Grimes, C.
(2003). Fabrication of tapered, conical-shaped titania nanotubes.
Journal of Materials Research, 18(11), 2588-2593. doi:
10.1557/JMR.2003.0362.
Currao, A. (2007). Photoelectrochemical Water Splitting. CHIMIA
International Journal for Chemistry, 61(12), 815-819. doi:
10.2533/chimia.2007.815.
62

Type Sample #
Peak Current Density (mA/cm2)
No Bias 0.5V 1V 1.5V 2V 2.5V
TiO2
021 0.42 0.50 0.54 0.62 0.69 0.82
022* 0.79 0.93 0.97 1.05 1.10 1.13
023 0.10 - - - - -
024 0.08 0.11 0.14 0.23 0.37 0.53
025 0.72 0.98 1.14 1.44 2.8 4
WO3
013 0.01 0.72 0.59 2.12 6.01 6.14
015 0.04 1.15 0.78 2.00 4.71 4.61
017 0.05 0.69 1.83 2.85 5.59 5.69
007 0.09 1.36 3.26 4.86 6.57 7.43
63

Electrolysis: Bipolar Design
 Alternating layers of
electrodes and separation
diaphragms clamped
together
 The cells are connected in a
series circuit and result in
higher stack voltages
 The bipolar design has
higher current densities and
produces higher-pressure
gas compared to that of the
unipolar, however if it needs
repair, the entire stack must
be replaced
73

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