nanostructured materials for solar fuel production
TRANSCRIPT
![Page 1: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/1.jpg)
Nanostructured Materials for Solar Fuel Production
Presented by: Mostafa Mamdouh
Under the supervision of:
Prof. Adel El-Shabasy
Assoc. Prof. Nageh Allam
![Page 2: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/2.jpg)
Contents
• Background on Energy Challenges• Why Water splitting for Hydrogen Production?
• Introduction to Water Splitting
• Research Plan
• Experimental Work
• Results
![Page 3: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/3.jpg)
Global Energy Challenge
![Page 4: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/4.jpg)
Egypt!
![Page 5: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/5.jpg)
Solar Fuel
• Light is used as an energy source, with solar energy being transduced to chemical energy typically by• reducing protons to hydrogen
or
• carbon dioxide to organic compounds.
• A solar fuel can be produced and stored for later usage, when sunlight is not available, making it an alternative to fossil fuels.
![Page 6: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/6.jpg)
Why Hydrogen?
• Clean – no greenhouse gases
• Energy security – can be produced from abundant sources
• Economic growth demands for energy
• Efficient – fuel cells ~75% efficiency
• Portable: Car tanks, micro fuel cells…
*New Materials for Photocatalytic Water Splitting, Fredrik Skullman, MATRL 286G, 05/26/2010
![Page 7: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/7.jpg)
Why Hydrogen?
Volumetric vs. gravimetric energy density plots of the major energy carriers.*
The hydrogen cycle in nature.*
Forecast of hydrogen production costs using different technologies.**
**Lemus, R. G.; Duart, J. M. M. Updated Hydrogen Production Costs and Parities for Conventional and Renewable Technologies. Int. J. Hydrogen Energy 2010, 35 (9), 3929–3936.
* Züttel, A.; Remhof, A.; Borgschulte, A.; Friedrichs, O. Hydrogen: The Future Energy Carrier. Philos. Trans. R. Soc. A Math. Phys. Eng. Sci. 2010, 368 (1923), 3329–3342.
![Page 8: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/8.jpg)
H2 Production Routes
• Our Proposed Solution:• Split water with renewable energy sources
![Page 9: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/9.jpg)
Water Splitting Principle
Schematic diagram of water electrolysis process.*
* Züttel, A.; Remhof, A.; Borgschulte, A.; Friedrichs, O. Hydrogen: The Future Energy Carrier. Philos. Trans. R. Soc. A Math. Phys. Eng. Sci. 2010, 368 (1923), 3329–3342.
![Page 10: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/10.jpg)
Splitting Water via Renewable Resources
• Direct PV electrolysis• connecting a commercial electrolyser to a
PV system.
• Light harvesting > charge generation > electrolysis > hydrogen and oxygen
• PEC electrolysis• Photoelectrode(s) are immersed into the
electrolyte and the photo-generated electron-holes are directly used to reduce and oxidize water.
L. Minggu et al. An overview of photocells and photoreactors for photoelectrochemical water splitting, International Journal of Hydrogen Energy, Vol. 35, 11, 2010 5233-5244.
![Page 11: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/11.jpg)
Splitting Water via Renewable Resources
• Direct PV electrolysis• Expensive?
• High current densities -> overpotential -> lower efficiency
• Not compact?
• PEC electrolysis• Lower current densities -> higher
electrolysis efficency
• All in one package: cheap, compact.
L. Minggu et al. An overview of photocells and photoreactors for photoelectrochemical water splitting, International Journal of Hydrogen Energy, Vol. 35, 11, 2010 5233-5244.
![Page 12: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/12.jpg)
PEC first demonstration
• First demonstration in 1972 by Fujishima and Honda,
Fujishima, A.; Honda, K. Electrochemical Photolysis of Water at a Semiconductor Electrode. Nature 1972, 238 (5358), 37–38.
![Page 13: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/13.jpg)
Development of the scientific field for Photo-Electrochemical Water Splitting research
97 108
6688 92 89 100
137 139160 157
200 211
294
383
517
620
766
937
0
100
200
300
400
500
600
700
800
900
1000
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
Nu
mb
er
of
Pu
blic
atio
ns
Publication Year
*Based on “Photo-Electrochemical Water Splitting” Keyword on Sciencedirect.com on 27/8/2016
![Page 14: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/14.jpg)
PEC WS Principle
• It combines the harvesting of solar energy and the electrolysis of water into a single device.
• PEC: Photoelectrochemical1. Photo
2. Electro
3. Chemical
![Page 15: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/15.jpg)
PEC Water Splitting Processes
• Incoming photons (hν) generate electrons (e-) and holes (h+) • with an efficiency labeled ηe-/h+
• The photogenerated electrons and holes then separate and travel through the semiconductor in opposite directions;• the efficiency associated with the charge
transport process is labeled ηtransport
• The holes drive the Oxygen Evolution Reaction at the surface of the semiconductor working electrode.
![Page 16: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/16.jpg)
Material criteria to be met
• The semiconductor system must generate sufficient voltage upon irradiation to split water• Or an external bias needs to be applied.
• The bulk band gap must be small enough to absorb a significant portion of the solar spectrum
• The band edge potentials at the surfaces must straddle the hydrogen and oxygen redox potentials Domen et al. New Non-Oxide Photocatalysts Designed for
Overall Water Splitting under Visible Light. J. Phys. Chem. 2007
![Page 17: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/17.jpg)
Material criteria to be met
• The system must exhibit long-term stability against corrosion in aqueous electrolytes • Metal oxides: Charge transfer kinetics >
anodic decomposition rate
• Non-oxides: thin oxide layer formation, dissolving.
• The charge transfer from the surface of the semiconductor to the solution must be facile to minimize energy losses due to kinetic overpotential
Domen et al. New Non-Oxide Photocatalysts Designed for Overall Water Splitting under Visible Light. J. Phys. Chem. 2007
![Page 18: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/18.jpg)
Target
• Band gap greater than 1.23 eV* but low enough to absorb visible light
• Band edge straddling
• High stability
• Fast charge transfer
• Low cost
![Page 19: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/19.jpg)
Current Challenge
• As far as we know, no cost-effective materials system satisfies all of the technical requirements listed above for practical hydrogen production.
• Schematic illustration of band structures of several semiconductor
*Chen, Z.; Dinh, H.; Miller, E. Photoelectrochemical water splitting.
Domen et al. New Non-Oxide Photocatalysts Designed for Overall Water Splitting under Visible Light. J. Phys. Chem. 2007
Problem
![Page 20: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/20.jpg)
Possible Solutions
• Materials Engineering• Introducing elements to reduce BG (Doping/Alloying)
• e.g.: N2
• Since N replaces O in certain positions, providing a smaller band gap.
• Nanostructuring• Increasing surface area
• Tuning electronic properties
• Different annealing conditions
![Page 21: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/21.jpg)
• In 1991, Iijima reported on the formation of carbon nanotubes• Milestone in MSE• Then transition to MOs
• quantum size and dimensionality may fully be effective on physical and chemical properties, such as electron mobility, optical band gap, and surface reactivity.
• NTs attracts tremendous interest due to specific advantages:• Geometric Factors:
• High surface area• Size exclusion effects• Diffusion behavior
• Biological Interactions• Directional Charge and Ion transport
Sep-17
Why NTs?
*Lee, Kiyoung, Anca Mazare, and Patrik Schmuki. "One-dimensional titanium dioxide nanomaterials: nanotubes." Chemical reviews 114.19 (2014): 9385-9454.
![Page 22: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/22.jpg)
• Classical 1D quantum size effects:• Reduced e- scattering (ballistic transport)• Extreme surface curvature (Modified physical and chemical properties)• Diffusion length of holes lies within the range of tube wall thickness• Orthogonal carrier separation:
• Hole to the wall• E- to the back contact
• Core shell Structures (Carrier Separation)• Decoration of wall ability• Nano test-tubes (high observation length)
• IPCE in NT >> NP layers• Since high current collection efficiency
• Since (Taw NT) (transport time constant) > NPs• Since surface recombination NT < NPs
Sep-17
Why NTs?
*Lee, Kiyoung, Anca Mazare, and Patrik Schmuki. "One-dimensional titanium dioxide nanomaterials: nanotubes." Chemical reviews 114.19 (2014): 9385-9454.
![Page 23: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/23.jpg)
• High surface area allows for increased photon absorption• Twice the surface area/unit volume compared to NPs and NRs with the same
outer diameter
• NTs perpendicular to the substrate surface, reduce e- diffusion path to the external circuit
Sep-17
Why NTs?
*Haring, Andrew, Amanda Morris, and Michael Hu. "Controlling morphological parameters of anodized titania nanotubes for optimized solar energy applications." Materials 5.10 (2012): 1890-1909.
![Page 24: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/24.jpg)
Sep-17
Why Ti?
Ghicov, Andrei, and Patrik Schmuki. "Self-ordering electrochemistry: a review on growth and functionality of TiO 2 nanotubes and other self-aligned MO x structures." Chemical Communications 20 (2009): 2791
• This is due to a broad set of outstanding properties that this class of materials has to offer.
Macak, J. M., et al. "TiO 2 nanotubes: self-organized electrochemical formation, properties and applications." Current Opinion in Solid State and Materials Science 11.1 (2007): 3
![Page 25: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/25.jpg)
• TiO2 has shown to be an excellent photocatalyst• long-term stability, low-cost preparation and a strong enough oxidizing power
to be useful for the decomposition of unwanted organic compounds
• The anatase form of TiO2 shows the highest solar energy conversion efficiency
Sep-17
Why TiO2?
Macak, J. M., et al. "TiO 2 nanotubes: self-organized electrochemical formation, properties and applications." Current Opinion in Solid State and Materials Science 11.1 (2007): 3-18.
![Page 26: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/26.jpg)
Main TiO2 Crystal Structures
Anatase
Rutile
![Page 27: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/27.jpg)
Sep-17
Why TNTs?
Indira, K., et al. "A Review on TiO2 Nanotubes: Influence of Anodization Parameters, Formation Mechanism, Properties, Corrosion Behavior, and Biomedical Applications." Journal of Bio-and Tribo-Corrosion 1.4 (2015): 1-22.
• Enhanced properties
• Cost-effective construction,
• higher surface-to-volume ratio
• Due to its photocatalytic property
![Page 28: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/28.jpg)
Proposed Material
• Ti 3510 • (Ti-35Zr-10Nb)
• Why?• The fabricated Ti-Nb-Zr-O nanotubes showed a 17.5% increase in the
photoelectrochemical water oxidation efficiency as compared to that measured for pure TiO2 nanotubes under UV illumination.
• Nb, Zr alloying • shifts absorption band edges towards visible region
• Enhances charge transfer
![Page 29: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/29.jpg)
Objective
• Fabrication of a complex metal oxide NTs and tuning its morphology for an efficient water splitting performance.
• Investigating the formation and growth of the NTs.
• Assessing the PEC performance of the fabricated NTs.
![Page 30: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/30.jpg)
Research Plan
• Literature Review on Water Splitting and different requirement for materials used.
• Selection of Material/Alloy.
• Material Preparation and Synthesis.
• Material Processing by Annealing at different temperatures and in different atmospheres.
• Studying the effect of different annealing conditions on the structure and properties of the material.
• Material characterization and assessment of the required properties for Water splitting.
![Page 31: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/31.jpg)
Experimental Methods
![Page 32: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/32.jpg)
Main Phases
1. NTs Synthesis• Via Anodization
• Optimization of anodization parameters
2. Morphology Investigation1. Studying effect of time
2. Studying effect of Anodization Potential
3. Selection of the most promising condition
3. Characterization
![Page 33: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/33.jpg)
I. NTs Synthesis
• Via Anodization
![Page 34: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/34.jpg)
Experimental Work
• Anodization
Allam, Nageh K., Faisal Alamgir, and Mostafa A. El-Sayed. "Enhanced photoassisted water electrolysis using vertically oriented anodically fabricated Ti− Nb− Zr− O mixed oxide nanotube arrays." ACS nano 4.10 (2010): 5819-5826.
Electrolyte Preparation
1.5 ml Distilled Water + 0.389 gm
NH4F
1 ml H3PO4 + 50 ml Formamide
+Anodization@ 40 V
Sample PreparationGrinding
and Polishing
Sonication (10 mins acetone >
10 mins ethanol > 10 mins distilled
water
+10 hrs
4 hrs
12 hrs
16 hrs
18 hrs
20 hrs
Time
Optimize Tube
Length, Diameter,
and thickness
![Page 35: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/35.jpg)
Sep-17
Sample Preparation
Grinded
Polished
Time0.5 h
1 h
2 h
4 h
6 h
8 h
10 h
12 h
14 h
16 h
18 h
20 h
Voltage
40 V
Anodization Conditions
![Page 36: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/36.jpg)
Sep-17
Sample Preparation
Grinded
Polished
Time2 hrs
4 hrs
8 hrs
14 hrs
Voltage
10 V
20 V
30 V
40 V
50 V
60 V
80 V
100 V
Anodization Conditions
![Page 37: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/37.jpg)
Anodization Time
2 hrs 4 hrs 8 hrs 14 hrs
An
od
izati
on
Pote
nti
al 10 V 10V/4hrs
20 V
30 V
40 V
50 V
60 V
80 V
100 V
![Page 38: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/38.jpg)
Sep-17
Temp.
500 °C
Ramp rate
1 °C/min
Atmospheres
H2
Air
Annealing Conditions
![Page 39: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/39.jpg)
3. Different Characterization Techniques Used
• Surface/Morphology:• SEM
• Structural:• X-ray Diffraction - XRD
• Elemental:• Energy-dispersive X-ray
spectroscopy - EDX
• X-ray photoelectron spectroscopy -XPS
• Optical:• UV-Vis Spectroscopy
• Raman Spectroscopy
• Electrochemical:• LSV
• I-t
![Page 40: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/40.jpg)
Results
![Page 41: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/41.jpg)
I. NTs Fabrication
![Page 42: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/42.jpg)
Sep-17
1. NTs Layer Adhesion
Good Adhesion Poor Adhesion ~ No Adhesion
![Page 43: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/43.jpg)
2. Effect of Surface roughness
Sep-17
18 hrs Polished18 hrs grinded
![Page 44: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/44.jpg)
Sep-17
Potential causes
• Electrolyte• Using same electrolyte
• Grinding / Polishing• Almost same conditions
• Sonication?• Pealed off even when drying under air stream!
• Fluorine rich layer?• Existed on both long and short times
Polished Grinded
18 hr (same electrolyte)
![Page 45: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/45.jpg)
Sep-17
Porous Layer instead of NTs!
![Page 46: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/46.jpg)
Effect of time and Anodization Potential
Sep-17
![Page 47: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/47.jpg)
Sep-17
10 V 30 V 50 V 60 V 80 V 100V
Effect of Anodization Potential on the Morphology
8 hrs 14 hrs2 hrs2 hrs 8 hrs 14 hrs4 hrs 8 hrs 14 hrs2 hrs 8 hrs 14 hrs2 hrs 4 hrs 14 hrs2 hrs 8 hrs 14 hrs
![Page 48: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/48.jpg)
Effect of Anodization Potential on the NTs Top pore
100 V/ 4 hrs80 V/4 hrs50 V/4 hrs
40 V/4 hrs30 V/4 hrs20 V/4 hrs
![Page 49: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/49.jpg)
Effect of Anodization Time on the Morphology
4 hrs 14 hrs2 hrs
100 V80 V60 V50 V40 V30 V20 V10 V
4 hrs 14 hrs2 hrs 8 hrs 14 hrs2 hrs 8 hrs 14 hrs4 hrs 4 hrs 8 hrs2 hrs4 hrs 8 hrs2 hrs 14 hrs4 hrs 8 hrs2 hrs 14 hrs4 hrs 8 hrs2 hrs 14 hrs
![Page 50: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/50.jpg)
Effect of Time on the Tube Walls
100 V/ 4 hrs60 V/8 hrs
40 V/2 hrs30 V/2 hrs10 V/2 hrs
50 V/4 hrs
![Page 51: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/51.jpg)
80 V/ 2 hrs 80 V/ 8 hrs
Base
Top
![Page 52: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/52.jpg)
60 V/ 8 hrs
![Page 53: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/53.jpg)
Ti3510 @ 40 V
Sep-17
![Page 54: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/54.jpg)
Sep-17
![Page 55: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/55.jpg)
• Initial Growth Rate)40 V= 9.4 × 103 (𝑛𝑚)
1 ×60 ×60 (𝑠)= 2.61 𝑛𝑚/𝑠𝑒𝑐
• Steady State Growth rate)40V= 0.198 nm/s
Sep-17
Growth rates
![Page 56: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/56.jpg)
5 min 10 min 15 min 30 min 1 hrs. 2 hrs.
Sep-17
Initial Growth Stage
![Page 57: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/57.jpg)
NTs Geometry Analysis
Sep-17
![Page 58: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/58.jpg)
Sep-17
![Page 59: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/59.jpg)
Sep-17
![Page 60: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/60.jpg)
• Migration of ions expressed as the max.radius of the oxide per applied potential
• D=2fgV
• .:.fg)Ti310= 2.6 nm/V•Compared to 2.5 nm/V
for TiO2
Sep-17
Anodic Growth Factor (fg)
Macak, J. M., et al. "TiO 2 nanotubes: self-organized electrochemical formation, properties and applications." Current Opinion in Solid State and Materials Science 11.1 (2007): 3-18.
![Page 61: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/61.jpg)
Sep-17
![Page 62: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/62.jpg)
Sep-17
4. 2,3 tubes -1 pore!
![Page 63: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/63.jpg)
Multipodal NTs Formation Mechanism
![Page 64: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/64.jpg)
![Page 65: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/65.jpg)
![Page 66: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/66.jpg)
![Page 67: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/67.jpg)
2 hrs
8 hrs
4 hrs
14 hrs
![Page 68: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/68.jpg)
2 hrs
8 hrs
4 hrs
![Page 69: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/69.jpg)
Taper Shape
d = 2fg × V
E =Vapplied − IRΩ
d
![Page 70: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/70.jpg)
![Page 71: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/71.jpg)
![Page 72: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/72.jpg)
![Page 73: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/73.jpg)
III. Characterization
![Page 74: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/74.jpg)
Material Characterization
• Structural
• Optical
• PEC
![Page 75: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/75.jpg)
EDX
![Page 76: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/76.jpg)
XRD
![Page 77: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/77.jpg)
XRD
![Page 78: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/78.jpg)
Raman Spectroscopy
![Page 79: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/79.jpg)
Raman Spectroscopy
Pure Ti annealed synthesized at the same conditions of the alloy.
![Page 80: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/80.jpg)
Raman Spectroscopy
The Raman peaks of pure titanium and the air-annealed alloy
showing the shift resulting from the alloying effect.
![Page 81: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/81.jpg)
XPS
XPS spectra of (a) Ti, (b) Nb, (c) Zr, and (d) O.
![Page 82: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/82.jpg)
Material Characterization
• Structural
• Optical
• PEC
![Page 83: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/83.jpg)
Absorbance
Absorbance of the TiO2 compared to the formed oxide
![Page 84: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/84.jpg)
Studying Multipodality Effect
Vs. Compact NTs
![Page 85: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/85.jpg)
Absorbance
Absorbance spectra of MPNTs and compact NTs
![Page 86: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/86.jpg)
Material Characterization
• Structural
• Optical
• PEC
![Page 87: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/87.jpg)
Linear Sweep Voltametry
Photoelectrochemical performance of MPNTs and compact NTs: (a) LSV, (b) normalized
Chronoamperometric measurements conducted at 0.5 V.
![Page 88: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/88.jpg)
H2 annealing confirming the Multipodal Effect
![Page 89: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/89.jpg)
Conclusions
![Page 90: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/90.jpg)
![Page 91: Nanostructured Materials for Solar Fuel Production](https://reader033.vdocuments.net/reader033/viewer/2022043013/626b7ca13f17ae72446fc7c5/html5/thumbnails/91.jpg)
Thank You