Platinum surface instabilities and their impact in electrochemistry

Valls Mascaro, F.

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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Platinum surface instabilities and their impact in electrochemistry

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