| dc.identifier.uri | http://hdl.handle.net/11401/76284 | |
| dc.description.sponsorship | This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. | en_US |
| dc.format | Monograph | |
| dc.format.medium | Electronic Resource | en_US |
| dc.language.iso | en_US | |
| dc.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dc.type | Dissertation | |
| dcterms.abstract | Fuel cells and water electrolysis, with their economical and environmental benefits, are expected to become major clean energy technologies. Hydrogen fuel cells use hydrogen as the carbon-free fuel to generate electricity with high efficiency, and water electrolysis can produce hydrogen from water using solar or wind power. However, the large-scale commercialization of these technologies has been impeded by the high cost of Pt catalysts necessary for their operation. To overcome this problem, in this study, core-shell architectures and monofaceted nanocrystals have been developed as two main approaches for rational design of electrocatalyst materials with enhanced activity, selectivity and durability. A series of bimetallic core-shell nanocatalysts having Ru core and Pt, Pd or Au shell (Ru@M, where M = Pt, Pd, Au) was synthesized using ethanol as the solvent and reducing agent. Their activities for the hydrogen evolution and oxidation reactions (HER-HOR) have been investigated in acid solution. It is found that Ru-Pt core-shell (Ru@Pt) nanocatalysts exhibited the highest HER-HOR activity among these bimetallic nanocatalysts. The optimal Pt shell thickness was determined by tuning the Ru to Pt atomic ratio. The key origin of improved catalytic properties was the formation of an ordered lattice structural transition from Ru(hcp) to Pt(fcc) at the core-shell interface, which was verified by XRD and STEM, coupled with DFT calculations. In situ XAS measurements were performed to investigate the local structures of Ru@Pt nanocatalysts. The well-defined bilayer Ru@Pt nanocatalysts, with optimized structures and improved Pt utilizations, demonstrated superior activity and durability for the HER-HOR, along with enhanced carbon monoxide tolerance of fuel cells H2 anodes. For the cathodic oxygen reduction reaction (ORR) in fuel cells, Pd-Pt core-shell (Pd@Pt) nanocatalysts with uniform and continuous Pt monolayer shell exhibited enhanced ORR activity in acid electrolyte. Further efforts in promoting the ORR activity were made by synthesizing Pt monolayer catalysts on hollow Pd and Pd-Au core nanoparticles. Electrochemistry of faceted nanocrystals was started by studies of Au monofaceted nanocrystals, which were used as a platform to uncover the structure-dependent ORR selectivity in alkaline media of single-crystalline Au facets. Nanocrystals' surface cleanness and crystallinity were confirmed by electrochemical characterizations including cyclic voltammetry and by signature voltammetry curves for thallium underpotential deposition. ORR pathways on single-crystalline facets, including {111} on octahedra and {100} on cubes, were similar to their single-crystal counterparts. In stark contrast, a full-range 4e-ORR in alkaline solution was discovered on {310} facets of Au nanocrystal shaped as the truncated ditetragonal prism (TDP). From analysis of experimental results and DFT calculations, the combination of low-coordinated Au surface sites and the dioxygen-water co-adsorption were proposed to result in the observed selectivity of the ORR pathway on Au nanocrystal surfaces. | |
| dcterms.available | 2017-09-20T16:49:55Z | |
| dcterms.contributor | Wang, Jia | en_US |
| dcterms.contributor | Adzic, Radoslav | en_US |
| dcterms.contributor | Halada, Gary | en_US |
| dcterms.contributor | Gang, Oleg. | en_US |
| dcterms.creator | Zhang, Yu | |
| dcterms.dateAccepted | 2017-09-20T16:49:55Z | |
| dcterms.dateSubmitted | 2017-09-20T16:49:55Z | |
| dcterms.description | Department of Materials Science and Engineering. | en_US |
| dcterms.extent | 220 pg. | en_US |
| dcterms.format | Application/PDF | en_US |
| dcterms.format | Monograph | |
| dcterms.identifier | http://hdl.handle.net/11401/76284 | |
| dcterms.issued | 2015-05-01 | |
| dcterms.language | en_US | |
| dcterms.provenance | Made available in DSpace on 2017-09-20T16:49:55Z (GMT). No. of bitstreams: 1
Zhang_grad.sunysb_0771E_12241.pdf: 9526615 bytes, checksum: 61d381eb4c0c6c54963168eae54bb24a (MD5)
Previous issue date: 2015 | en |
| dcterms.publisher | The Graduate School, Stony Brook University: Stony Brook, NY. | |
| dcterms.subject | Materials Science | |
| dcterms.title | Core-Shell and Monofaceted Nanocatalysts for Fuel Cells and Water Electrolysis | |
| dcterms.type | Dissertation | |
