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Colorado State University

1. Folkman, Scott Jerald. Water oxidation catalysis beginning with cobalt polyoxometalates: determining the dominant catalyst under electrocatalytic conditions and investigation of the surface properties of Co3O4 nanoparticles.

Degree: PhD, Chemistry, 2018, Colorado State University

Generation of hydrogen as a fuel is one of the most promising technologies for a renewable energy future. Electrocatalytic water splitting can take energy from virtually any power source and split water into oxygen and hydrogen, thereby creating a renewable feedstock of hydrogen. The efficiency of electrocatalytic water splitting is limited by the anodic half reaction, water oxidation. As such, there has been an immense effort to discover and understand water oxidation catalysts (WOCatalysts). The two main classes of WOCatalysts are homogeneous and heterogeneous catalysts. Homogeneous catalysts are typically soluble molecular complexes that have a single type of active site, allowing for rational tuning through synthesis, and mechanistic studies. Heterogeneous catalysts are typically in a different phase from the reaction (i.e. insoluble or electrode-bound) and have a spectrum of active sites that are more difficult to identify. This Dissertation examines a class of inorganic compounds called polyoxometalates (POMs), and investigates the nature of the kinetically dominant, homogeneous vs heterogeneous catalyst. Chapter I provides an in depth introduction to water oxidation catalysis and in particular with cobalt-based POMS. Chapters II and III focus on the polyoxometalate, [Co4(H2O)2(VW9O34)2]10− (hereafter Co4V2W18) which has been claimed to be one of the fastest WOCatalysts to date. Those studies demonstrate that Co4V2W18 is, in fact, very unstable and dissociates 87-100% of the Co(II) originally present in Co4V2W18 into solution within three hours when dissolved in 0.1 sodium phosphate buffer (NaPi) at pH 5.8 and 8.0 as well as sodium borate buffer (NaB) pH=9.0. The dissociated Co(II)aq then forms heterogeneous cobalt-oxide (CoOx) on a glassy carbon electrode under electrocatalytic WOCatalysis conditions. The deposited CoOx accounts for 100±15% of the observed catalysis current. This finding demonstrates that the original Co4V2W18 serves only as a precursor to heterogeneous CoOx which is the dominant WOCatalyst. Chapter IV details studies using a selection of the most stable and most active Co-POMs to date. These studies demonstrate that none of the Co-POMs examined are 100% stable, and they release between 0.6 and >90% of the cobalt in the original complex within three hours in 0.1 M NaPi pH=5.8 or 8.0 and NaB pH=9.0. Furthermore, in 13 of the 18 cases examined, heterogeneous CoOx forms on the glassy carbon electrode and accounts for ≥100% of the observed WOCatalysis current. Lastly, under conditions where the Co-POMs are stable (<2% decomposition), the evidence provided implies that some of the Co-POMs are homogeneous WOCatalyst. Other implications regarding the stability trends and nature of the true catalyst are provided. The last research chapter, Chapter V, consists of the study of Co3O4 nanoparticles, which have been shown to be active for WOCatalysis. In this chapter, the synthesis, and surface properties of Co3O4 nanoparticles are investigated. It is demonstrated that ethanol/water (EtOH/water) as… Advisors/Committee Members: Finke, Richard G. (advisor), Neilson, James (committee member), Strauss, Steven (committee member), Sites, James (committee member).

Subjects/Keywords: cobalt oxide; homogeneous vs. heterogeneous; water oxidation; electrocatalytic; catalysis; polyoxometalate

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APA (6th Edition):

Folkman, S. J. (2018). Water oxidation catalysis beginning with cobalt polyoxometalates: determining the dominant catalyst under electrocatalytic conditions and investigation of the surface properties of Co3O4 nanoparticles. (Doctoral Dissertation). Colorado State University. Retrieved from http://hdl.handle.net/10217/191355

Chicago Manual of Style (16th Edition):

Folkman, Scott Jerald. “Water oxidation catalysis beginning with cobalt polyoxometalates: determining the dominant catalyst under electrocatalytic conditions and investigation of the surface properties of Co3O4 nanoparticles.” 2018. Doctoral Dissertation, Colorado State University. Accessed March 04, 2021. http://hdl.handle.net/10217/191355.

MLA Handbook (7th Edition):

Folkman, Scott Jerald. “Water oxidation catalysis beginning with cobalt polyoxometalates: determining the dominant catalyst under electrocatalytic conditions and investigation of the surface properties of Co3O4 nanoparticles.” 2018. Web. 04 Mar 2021.

Vancouver:

Folkman SJ. Water oxidation catalysis beginning with cobalt polyoxometalates: determining the dominant catalyst under electrocatalytic conditions and investigation of the surface properties of Co3O4 nanoparticles. [Internet] [Doctoral dissertation]. Colorado State University; 2018. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/10217/191355.

Council of Science Editors:

Folkman SJ. Water oxidation catalysis beginning with cobalt polyoxometalates: determining the dominant catalyst under electrocatalytic conditions and investigation of the surface properties of Co3O4 nanoparticles. [Doctoral Dissertation]. Colorado State University; 2018. Available from: http://hdl.handle.net/10217/191355


Georgia Tech

2. Richardson, John Michael. Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons.

Degree: PhD, Chemical and Biomolecular Engineering, 2008, Georgia Tech

This work focuses on understanding the heterogeneous/homogeneous nature of the catalytic species for a variety of immobilized metal precatalysts used for C-C coupling reactions. These precatalysts include: (i) tethered organometallic palladium pincer complexes, (ii) an encapsulated small molecule palladium complex in a polymer matrix, (iii) mercapto-modified mesoporous silica metalated with palladium acetate, and (iv) amino-functionalized mesoporous silicas metalated with Ni(II). As part of this investigation, the use of metal scavengers as selective poisons of homogeneous catalysis is introduced and investigated as a test for distinguishing heterogeneous from homogeneous catalysis. The premise of this test is that insoluble materials functionalized with metal binding sites can be used to selectively remove soluble metal, but will not interfere with catalysis from immobilized metal. In this way the test can definitely distinguish between surface and solution catalysis of immobilized metal precatalysts. This work investigates three different C-C coupling reactions catalyzed by the immobilized metal precatalysts mentioned above. These reactions include the Heck, Suzuki, and Kumada reactions. In all cases it is found that catalysis is solely from leached metal. Three different metal scavenging materials are presented as selective poisons that can be used to determine solution vs. surface catalysis. These selective poisons include poly(vinylpyridine), QuadrapureTM TU, and thiol-functionalized mesoporous silica. The results are contrasted against the current understanding of this field of research and subtleties of tests for distinguishing homogeneous from heterogeneous catalysis are presented and discussed. Advisors/Committee Members: Dr. Christopher W. Jones (Committee Chair), Dr. E. Kent Barefield (Committee Member), Dr. Marcus Weck (Committee Member), Dr. Pradeep Agrawal (Committee Member), Dr. Rachel Chen (Committee Member).

Subjects/Keywords: Palladium catalysis; Cross coupling reaction; Heterogeneous vs. homogeneous; Selective poisoning; Palladium catalysts; Heterogeneous catalysis; Catalysis; Catalyst poisoning

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Richardson, J. M. (2008). Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/22704

Chicago Manual of Style (16th Edition):

Richardson, John Michael. “Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons.” 2008. Doctoral Dissertation, Georgia Tech. Accessed March 04, 2021. http://hdl.handle.net/1853/22704.

MLA Handbook (7th Edition):

Richardson, John Michael. “Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons.” 2008. Web. 04 Mar 2021.

Vancouver:

Richardson JM. Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/1853/22704.

Council of Science Editors:

Richardson JM. Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/22704

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