On 28 August at 10.15 Raegan Danielle Chambers will defend her doctoral thesis „Electrocatalysis of oxygen reduction on Pt nanoparticles deposited on novel support materials“.
Supervisors:
Dr. Heiki Erikson, Institute of Chemistry, University of Tartu
Prof. Kaido Tammeveski, Institute of Chemistry, University of
Oponendid:
Prof. Rakel Wreland Lindstöm, Department of Chemical Engineering, KTH-Royal Institute of Technology, Sweden
Summary:
The aim of this thesis was to investigate the effects the carbon support material on the overall electrocatalytic activity of Pt nanoparticles (PtNPs) for the oxygen reduction reaction (ORR) in acid media and in proton exchange membrane fuel cells (PEMFCs). Different functionalized carbon materials were used as supports for PtNPs, which were deposited onto the carbons using two different methods: chemical and electrochemical deposition. The synthesized catalysts were characterized by N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray fluorescence spectroscopy (XRF), and Raman spectroscopy. The electrochemical properties of the electrocatalysts were examined via cyclic voltammetry (CV), CO-stripping, the rotating disk electrode (RDE) method and single-cell PEMFC tests. In the first part of the PhD thesis, the PtNPs were electrochemically deposited onto different commercially available heteroatom-doped graphenes. There was a trend that the PtNPs electrochemically deposited onto single heteroatom-doped graphenes had a higher specific activity for ORR than those supported on dual heteroatom-doped graphenes. This was the opposite of what was found in the second part of the thesis, in which PtNPs were chemically deposited onto different heteroatom-doped graphenes. In the third part of this thesis, PtNPs were deposited onto nitrogen-doped porous carbon. In this study it was found that the chemical deposition method used had an influence on the electrocatalytic activity and PEMFC performance of the catalyst. In the final part of the thesis, PtNPs were chemically deposited onto SnO2-coated carbon nanotubes. This catalyst exhibited superior stability compared to the commercially available 20% Pt/C catalyst. The works presented in this study confirm that optimizing a carbon support is imperative, as it directly impacts the overall electrocatalytic activity of PtNPs for ORR.
