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Valls Mascaro, F. (2024)

Platinum surface instabilities and their impact in electrochemistry

Doctoral Thesis
Hydrogen fuel cells are expected to be pivotal in the energetic transition towards renewable energy sources such as solar and wind power. However, their industrial scalability is severely hindered by the high cost and degradation rate of platinum catalysts, one of their key components. Addressing this challenge necessitates developing better catalysts, which requires a better fundamental understanding of their reactivity and degradation mechanism. In this thesis, we investigate the (in)stability of model platinum surfaces submerged in liquid and under applied voltage, thus simulating the operational conditions of fuel cells. For this we use a home-build Electrochemical Scanning Tunneling Microscope (EC-STM), which allows us to observe, in real time, the surface structure at the atomic scale. Our findings elucidate the origin of the platinum surface roughening that takes place upon voltage cycling. Moreover, we demonstrate that closely-spaced atomic steps are prone to bunch...Show moreHydrogen fuel cells are expected to be pivotal in the energetic transition towards renewable energy sources such as solar and wind power. However, their industrial scalability is severely hindered by the high cost and degradation rate of platinum catalysts, one of their key components. Addressing this challenge necessitates developing better catalysts, which requires a better fundamental understanding of their reactivity and degradation mechanism. In this thesis, we investigate the (in)stability of model platinum surfaces submerged in liquid and under applied voltage, thus simulating the operational conditions of fuel cells. For this we use a home-build Electrochemical Scanning Tunneling Microscope (EC-STM), which allows us to observe, in real time, the surface structure at the atomic scale. Our findings elucidate the origin of the platinum surface roughening that takes place upon voltage cycling. Moreover, we demonstrate that closely-spaced atomic steps are prone to bunch together, resulting in steps with multi-atomic height. This structural change has a significant effect on the catalyst reactivity, as we explain in detail. Overall, this dissertation contributes to a deeper fundamental understanding of the surface processes that drive platinum surface restructuring as well as their implications for reactivity.
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Electrochemistry
Surface Science
Electrochemical Scanning Tunneling Microscopy
Platinum
Nucleation and Growth
Adatom Islands
Steps
Step Bunching (Instability)
Adsorption
Oxidation-Reduction Cycling
All authors
Valls Mascaro, F.
Supervisor
Koper, M.T.M.; Rost, M.J.
Committee
Ubbink, M.; Groot, I.M.N.; Ruitenbeek, J.M. van; Magnussen, O.M.; Zandvliet, H.J.W.
Qualification
Doctor (dr.)
Awarding Institution
Leiden Institute of Chemistry (LIC), Faculty of Science, Leiden University
Date
2024-09-05
ISBN (print)
9789090385129

Funding

Sponsorship
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)