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J Barnett

on 4 May 2013

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Transcript of Thesis

Jett Barnett
Dr. Cleary Photo-catalytic Water Splitting With Rare Earth Metal Oxides -Dissociation of two O-H bonds
-Reduction-Oxidation chemistry

2H 0 2H + O What is Water Splitting? -its MW is low
-can be stored as either a gas or liquid
-can be used whenever with no degradation

not to mention - instead of CO and CO2 emissions, H2 use gives off water

it also can give us about 237 kJ/mol H2O, which is about 13 MJ/ L H2O Hydrogen As An Energy Carrier Using metal oxide catalysts How? Digamber G. Porob, Paul A. Maggard, Flux syntheses of La-doped NaTaO3 and its photocatalytic activity, Journal of Solid State Chemistry, Volume 179, Issue 6, June 2006, Pages 1727-1732, ISSN 0022-4596, 10.1016/j.jssc.2006.03.008.
Keywords: Sodium tantalate (NaTaO<sub>3</sub>); Flux synthesis; Photocatalysis NaTaO3:La has an
activity of 16.8 mmol/h

(Kato, H. et al. Highly Efficient Water Splitting into H2 and O2 over Lanthanum-Doped NaTaO3 Photocatalysts with High Crystallinity and Surface Nanostructure. J. Am. Chem. Soc. 2003, 125, pp. 3082-3089. doi: 10.1021/ja027751g) The Math 16.8 mmol H2 1 mol 237 kJ 1 hour 1000 mmol 1 mol H2 x x = 3.98 kJ/h which is about 1.11 W Though, this may not seem like much, this is for an experimental setup of 1 g of NaTaO3:La, 390 mL water, and a 400 W Hg lamp (Kato, et al., 2002) David Mack/SciencePhotoLibrary: http://www.sciencephoto.com/media/437247/enlarge# Why Rare earth metals? Or if you prefer...

the NaTaO3:La has a quantum yield of 56% at 270 nm

Refresher on that math;

apparent quantum yield (%) = (100%) the number of reacted electrons

the number of incident photons limited research has been done here
Incompletely Localized electron configuration, which influences the band structure

(Machida, Masato et al. Photocatalytic properties of layered perovskite tantalates, MLnTa2O7 (M=Cs, Rb, Na, and H; Ln=La, Pr, Nd, and Sm). Journal of Materials Chemistry (2003), Vol. 13, No. 6, pp. 1433-1437) It is necessary, for the sake of water splitting, that these semiconductor photocatalysts have conduction band levels more negative than the reduction potential of H2O to produce H2 (-0.83 V) and valence bands more positive than the oxidation potential of H2O to produce O2 (-1.23 V). www.solarcentral.com (modified) (Kato, H. et al. Highly Efficient Water Splitting into H2 and O2 over Lanthanum-Doped NaTaO3 Photocatalysts with High Crystallinity and Surface Nanostructure. J. Am. Chem. Soc. 2003, 125, pp. 3082-3089. doi: 10.1021/ja027751g) Synthesis of REM Oxides
Is Fairly Straightforward Take for example K2SmTa5O15 (2726.1 g/mol) Add molar equivalents of K2CO3, CeO2, and Ta2O5
to a ceramic crucible/boat

Bake at 1100 C for 10 hours Other considerations to
Rare Earth Metal
Oxides but there is a bit more math left we could do... Avista charges about 0.08063 cents per kWh

...and from earlier, we mentioned that the world uses 474 EJ/ yr

which is equivalent to 132,000,000,000 kWh (or $10.5 billion dollars)

the research seems to be potentially profitable .......-1.23 V .......-0.83 V As REM become an increasing technological necessity over the past several decades, demand for several of the less abundant (and formerly quite obscure) REMs has increased exponentially. Department of the Interior,http://pubs.usgs.gov/fs/2002/fs087-02 (2005) China's Monopoly (l) (g) (g) "In fact, electron transfer in the PbRC is so efficient that its overall quantum yield [...] is virtually 100%. No man-made device has yet approached this level of efficiency." Voet, Voet, and Pratt. Fundamentals of Biochemistry (2008). metal semiconductor Fermi level Characterization and physical properties - X-ray diffraction
- Photoelectrochemical Cell A member in the Chinese commerce announced China will"further reduce quotas for rare earth exports by 30 percent at most next year to protect the precious metals from over-exploitation" China to cut exports of rare earth minerals vital to energy tech" thehill.com, 19 Oct. 2009. Retrieved 2010-10-19. Energy Is Important. - World wide use: 474 exajoules, rate of 15 TW [1] -Increasing demand (1990-2008) [1]
Middle East increased by 170%
China by 146%
India by 91%
World by 39% -Most of this was not reusable, clean nor efficiently used (e.g. 2/3 of nuclear power energy is lost when cooling water is considered) [2]. 1."Key World Energy Statistics" (PDF). International Energy Agency. 2006. Retrieved 3 April 2007. pp. 48–57
2. Energy in Sweden 2010, Facts and figures Table 46 Total world energy supply, 1990–2009 Where The Energy Comes From Renewables 2012 Global Status Report. http://www.map.ren21.net/GSR/GSR2012.pdf. gram of product, water, and a lamp An example of a setup requires a Acknowledgments -Dr. David Cleary
-Dr. Joanne Smieja
-Scholl Foundation
-Dr. Jennifer Schuttlefield, U Wisconsin Oshkosh
-Dr. Jeff Cronk : : : : Synthesis and Characterization - high temperature
-intermediary grinding
-higher temperature -X-ray diffraction
-Photoelectrochemical cell > > Iron (III) Oxide spotted at Row [1,2] and Columns [2,5]. Undoped K Ce Ta O R[3,4] and C[1,7]. Doped K Ce Ta O R[5,6] and C[1,7]. Bias of 0.2 V. Iron (III) Oxide spotted at Rows [0,1] and Columns [2,4]. Undoped K Ce Ta O R[3,4] and C[1,7]. Doped K Ce Ta O R[5,6] and C[1,7]. Bias of -0.2 V. No additional light. Globular method used. Iron oxide responded. Doped and non-doped compounds were placed in approximately C[4,5] and C[6,7] At a negative bias, everything but the iron oxide gave a reading. Globular method, Iron responding to a .4 V bias, conc. nitric acid as solvent CuO responding on the same plate, iron below the baseline, -0.6 V, doped C[3,5] and nondoped [6,8] compounds plotted. Future Work Use a photoelectochemical cell monitored by GC
Determine the effects of using lanthanum as a doping agent
Successfully tune the LED array system to detect photocatalytic water splitting materials

Facile synthesis possible
Ancillary techniques for characterization
Protocol for using the LED array
Method for producing thin films for further testing In Conclusion The Language We Use Not always the case, though it theoretically
should be Literature Synthesized Literature Synthesized Literature Synthesized Literature Synthesized ABO 3 Structure of Perovskites 2 2 2 4 2 10 30 4 2 10 30 4 2 10 30 4 2 10 30 10CeO + 10K CO + 24Ta O K Ce Ta O + 10CO 2 2 3 2 5 4 2 10 30 2 (g) ∆ Solids, a very light yellow mixture Pure perovskites look something like ABO
as in CaTiO 3 3 A B O (http://www.uwgb.edu/dutchs/Petrology/Perovskite%20Structure.HTM, modified) (http://www.msm.cam.ac.uk/ascg/materials/photocatalysis/energydiagram.gif, modified)
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