Photocatalytic water splitting

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dc.contributor.author Khnayzer, Rony S.
dc.date.accessioned 2017-11-07T07:48:52Z
dc.date.available 2017-11-07T07:48:52Z
dc.date.copyright 2013 en_US
dc.date.issued 2017-11-07
dc.identifier.uri http://hdl.handle.net/10725/6523
dc.description.abstract Due to the expected increases on energy demand in the near future, the development of new catalytic molecular compositions and materials capable of directly converting water, with the aid of solar photons, into hydrogen becomes obviated. Hydrogen is a combustible fuel and precious high-energy feedstock chemical. However, for the water-splitting reaction to proceed efficiently and economically enough for large-scale application, efficient light-absorbing sensitizers and water splitting catalysts are required. To study the kinetics of the water reduction reaction, we have used titania (TiO2) nanoparticles as a robust scaffold to photochemically grow platinum (Pt) nanoparticles from a unique surface-anchored molecular precursor Pt(dcbpy)Cl2 [dcbpy = 4,4`-dicarboxylic acid-2,2`-bipyridine]. The hybrid Pt/TiO2 nanomaterials obtained were shown to be a superior water reduction catalyst (WRC) in aqueous suspensions when compared with the benchmark platinized TiO2. In addition, cobalt phosphate (CoPi) water oxidation catalyst (WOC) was photochemically assembled on the surface of TiO2, and its structure and mechanism of activity showed resemblance to the established electrochemically grown CoPi material. Both WRC and WOC described above possessed near unity Faradaic efficiency for hydrogen and oxygen production respectively, and were fully characterized by electron microscopy, x-ray absorption spectroscopy, electrochemistry and photochemistry. While there are established materials and molecules that are able to drive water splitting catalysis, some of these efficient semiconductors, including titanium dioxide (TiO2) and tungsten trioxide (WO3), are only able to absorb high-energy (ultraviolet or blue) photons. This high-energy light represents merely a fraction of the solar spectrum that strikes the earth and the energy content of those remaining photons is simply wasted. A strategy to mitigate this problem has been developed over the years in our laboratory. Briefly, photons of low energy are converted into higher energy light using a process termed photon upconversion. Using this technique, low energy photons supplied by the sun can be converted into light of appropriate energy to trigger electronic transitions in high energy absorbing photoactive materials without any chemical modification of the latter. We have shown, that this technology is capable of upconverting visible sunlight to sensitize wide-bandgap semiconductors such as WO3, subsequently extending the photoaction of these materials to cover a larger portion of the solar spectrum. Besides the engineering of different compositions that serve as either sensitizers or catalysts in these solar energy conversion schemes, we have designed an apparatus for parallel high-throughput screening of these photocatalytic compositions. This combinatorial approach to solar fuels photocatalysis has already led to unprecedented fundamental understanding of the generation of hydrogen gas from pure water. The activity of a series of new Ru(II) sensitizers along with Co(II) molecular WRCs were optimized under visible light excitation utilizing different experimental conditions. The multi-step mechanism of activity of selected compositions was further elucidated by pump-probe transient absorption spectroscopy. en_US
dc.language.iso en en_US
dc.subject Photocatalysis -- Case studies. en_US
dc.subject Electrocatalysis -- Case studies. en_US
dc.subject Water -- Case studies en_US
dc.subject Oxygen -- Case studies en_US
dc.subject Hydrogen -- Case studies en_US
dc.title Photocatalytic water splitting en_US
dc.type Thesis en_US
dc.title.subtitle materials design and high-throughput screening of molecular compositions en_US
dc.author.degree PHD en_US
dc.author.school SAS en_US
dc.author.idnumber 200501196 en_US
dc.author.department Natural Sciences en_US
dc.description.embargo N/A en_US
dc.description.physdesc xvii, 174 p: ill en_US
dc.author.advisor Castellano, Felix N.
dc.description.bibliographiccitations Includes bibliographical references en_US
dc.identifier.ctation Khnayzer, R. S. (2013). Photocatalytic water splitting: Materials design and high-throughput screening of molecular compositions. Bowling Green State University. en_US
dc.author.email rony.khnayzer@lau.edu.lb en_US
dc.identifier.tou http://libraries.lau.edu.lb/research/laur/terms-of-use/articles.php en_US
dc.identifier.url https://etd.ohiolink.edu/pg_10?0::NO:10:P10_ACCESSION_NUM:bgsu1368627386#abstract-files en_US
dc.orcid.id https://orcid.org/0000-0001-7775-0027 en_US
dc.publisher.institution Bowling Green State University en_US
dc.author.affiliation Lebanese American University en_US

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