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Fuels and Materials from Sunlight and Water

Citation

Hunter, Bryan Michael (2017) Fuels and Materials from Sunlight and Water. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9FQ9TNB. http://resolver.caltech.edu/CaltechTHESIS:06022017-112043547

Abstract

The urgency to develop new technologies that harness energy and natural feedstocks in a sustainable fashion has never been more apparent. With global power consumption growing at an exponential rate, only one resource is truly capable of powering the planet: the sun. Sunlight is reliable, clean, and free.

Significant resources have been pledged to develop and refine solar energy devices that convert photons into electricity (i.e. photovoltaics), but the sun’s intermittency and the poor overlap of solar irradiance with global power demand a different strategy. In light of these limitations, we have proposed a device which converts solar energy into reduced chemical fuels (e.g. dihydrogen or methane) that can be indefinitely stored and easily transported. In principle, the only required inputs are sunlight, an earth-abundant feedstock such as carbon dioxide, protons (H+), and reducing equivalents (e-). The source of these protons and electrons must be abundant and ubiquitous—we chose water.

Despite the 2-billion-year history of plants performing water oxidation to produce molecular oxygen, protons, and electrons (Photosystem II), our understanding of this complex 4H+/4e- process has been severely limited. Only recently have high-performing, earth-abundant heterogeneous electrocatalysts been reported that can be scaled up to make functioning devices.

This dissertation describes progress on both the synthetic and mechanistic fronts in developing earth-abundant heterogeneous water oxidation catalysts for solar-driven water splitting. We have synthesized nanoparticulate Ni-Fe catalysts with the highest measured activity on flat electrodes to date. We carefully characterized these materials spectroscopically to determine that edge-site iron was active in catalysis. We then undertook novel in-situ spectroelectrochemical techniques in non-aqueous media to identify the active iron species, which is surprisingly a cis-dioxo-iron(VI) corner site. The data also indicate that geminal iron-oxo coupling may be the operative mechanism of O-O bond formation, a new scheme with potential biological relevance.

Finally, we have expanded our goal to include sustainably reducing other feedstocks, such as carbon dioxide and hydrocarbons. In doing so, we aim to make pharmaceuticals, polymers, and other high-value products from sunlight and water.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:renewable energy; water oxidation; solar fuels; electrocatalysis; catalysis; layered double-hydroxide; [NiFe]-LDH
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Awards:Demetriades-Tsafka-Kokkalis Prize in Benign Renewable Energy Sources or Related Fields, 2017. The Herbert Newby McCoy Award, 2017
Thesis Availability:Mixed availability, specified at file level
Research Advisor(s):
  • Gray, Harry B.
Thesis Committee:
  • Barton, Jacqueline K. (chair)
  • Gray, Harry B.
  • Rossman, George Robert
  • Rees, Douglas C.
Defense Date:26 May 2017
Non-Caltech Author Email:bryan.m.hunter (AT) gmail.com
Funders:
Funding AgencyGrant Number
National Science Foundation Graduate Research FellowshipUNSPECIFIED
National Science FoundationCHE-1305124
Resnick Sustainability InstituteUNSPECIFIED
Record Number:CaltechTHESIS:06022017-112043547
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:06022017-112043547
DOI:10.7907/Z9FQ9TNB
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/acs.chemrev.6b00398DOIArticle adapted for Chapter 1.
http://dx.doi.org/10.1021/ja506087hDOIArticle adapted for Chapter 2.
http://dx.doi.org/10.1039/C6EE00377JDOIArticle adapted for Chapter 3.
http://dx.doi.org/10.1002/ange.201600856DOIArticle reproduced for Appendix A.
http://dx.doi.org/10.1021/ic300716qDOIArticle reproduced for Appendix B.
http://dx.doi.org/10.1021/jacs.6b02559DOIArticle reproduced for Appendix C.
http://dx.doi.org/10.1021/acs.inorgchem.6b03001DOIArticle reproduced for Appendix D.
ORCID:
AuthorORCID
Hunter, Bryan Michael0000-0001-8559-9304
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10253
Collection:CaltechTHESIS
Deposited By: Bryan Hunter
Deposited On:03 Jun 2017 00:12
Last Modified:29 Sep 2017 21:30

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