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Combinatorial discovery and optimization of novel metal oxide materials for photoelectrolysis using visible light

dc.contributor.authorWoodhouse, Michael, author
dc.contributor.authorParkinson, Bruce, advisor
dc.description.abstractEfficient and inexpensive production of hydrogen from water and sunlight has been the "holy grail" of photoelectrochemistry since Fujishima and Honda first demonstrated the feasibility of the process by illuminating TO2 single crystals with UV light. While it was a great proof of concept, a more suitable material will most likely be an oxide semiconductor containing multiple metals that will each contribute to the required properties of stability, light absorption, and being catalytic for hydrogen or oxygen evolution. Therefore we developed a high throughput combinatorial approach to prepare overlapping patterns of metal oxide precursors onto conducting glass substrates that can be screened for photolectrolysis activity by measuring the photocurrent generated by rasterng a laser over the materials while they are immersed in an electrolyte. A ternary oxide containing cobalt, aluminum and iron, and not previously known to be active for the photoelectrolysis of water, was identified using the combinatorial technique. The optimal composition and thickness for photoelectrochemical response of the newly identified material has been further refined using quantitative ink jet printing. Chemical analysis of bulk and thin film samples revealed that the material contains cobalt, aluminum and iron in a Co3O 4 spinel structure with Fe and Al substituted into Co sites with a nominal stoichiometry of Co3-x-yAlxFeyO4 where x and y are about 0.18 and 0.30 respectively. The material is a p-type semiconductor with an indirect band gap of around 1.5 eV, a value that is nearly ideal for the efficient single photoelectrode photoelectroylsis of water. Photoelectrochemical measurements indicate that the material has a respectable photovoltage but the photocurrent is limited by the slow kinetics for hydrogen evolution. This new cobalt iron aluminum oxide is most likely not the "holy grail" of photoelectrochemistry that we seek, but our methodology gives a rational approach for future materials discovery and optimization.
dc.format.mediumborn digital
dc.format.mediumdoctoral dissertations
dc.publisherColorado State University. Libraries
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dc.rights.licensePer the terms of a contractual agreement, all use of this item is limited to the non-commercial use of Colorado State University and its authorized users.
dc.subjectmetal oxides
dc.subjectvisible light
dc.subjectanalytical chemistry
dc.subjectphysical chemistry
dc.titleCombinatorial discovery and optimization of novel metal oxide materials for photoelectrolysis using visible light
dcterms.rights.dplaThis Item is protected by copyright and/or related rights ( You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). State University of Philosophy (Ph.D.)


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