THESIS
2005
xv, 101 leaves : ill. ; 30 cm
Abstract
Polymer electrolyte fuel cells (PEFCs) have a high energy density and low temperature operation, with potential applications in automobiles and portable electronics. But low catalyst utilization and high cost of noble metal based electrocatalysts have prevented PEFCs from a large scale deployment in the commercial market. This thesis studies the approach of using surfactant stabilizers to synthesize well-dispersed nanoscale electrocatalysts for PEFCs....[
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Polymer electrolyte fuel cells (PEFCs) have a high energy density and low temperature operation, with potential applications in automobiles and portable electronics. But low catalyst utilization and high cost of noble metal based electrocatalysts have prevented PEFCs from a large scale deployment in the commercial market. This thesis studies the approach of using surfactant stabilizers to synthesize well-dispersed nanoscale electrocatalysts for PEFCs.
Two surfactants with different synthesis environments are investigated. In the first approach, surfactant tetraoctylammonium bromide (TOAB) acts as the stabilizer in an organic environment, well-separated Pt/C catalysts are formed with the use of formic acid as the reducing agent. Molar ratio of the surfactant to the platinum precursor is demonstrated to have significant impact on the dispersion and particles size of the catalysts. Electrochemical measurements show the catalysts synthesized at a high molar ratio posses higher active surface area and activity.
The second part of this work focuses on the preparation and characterization of dodecyldimethyl (3-sulfo-propyl) ammonium hydroxide (SB12) stabilized electrocatalysts. Dispersion and particles size of the nanoplatinum have been identified to depend on the pH environment. A neutral or slightly alkaline environment is beneficial to the formation of well-dispersed nanocatalysts. Electrochemical measurements of the resultant catalysts exhibit higher activities in the fuel cell environment that those at a low pH environment. Besides, SB12-stabilization method is applied on carbon nanotubes (CNTs) supported catalysts. Effect of oxidative treatments on the CNTs is investigated and performances of the Pt/CNTs are compared with Pt/C.
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