Electrochemical hydride formation in thin Pd films analyzed with a combined optical and electrochemical technique
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Nanotechnology (MPNAT), MSc
Publicerad
2014
Författare
Fredriksson, Mattias
Modellbyggare
Tidskriftstitel
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Volymtitel
Utgivare
Sammanfattning
The main objective of this work was to investigate how UV/Vis spectroscopy and electrochemical techniques can be combined to gain more information about the hydride formation in palladium thin-films. By controlling the potential in the electrochemical circuit, it is possible to control the hydride formation and by measuring the current, the amount of hydride formed can be quantified. Optical measurements were done in transmission and reflection mode and the response was synchronized with the electrochemical data. Focus has been on hydride formation in palladium films of thickness 20 and 100 nm. The 100nm films have been measured with reflection measurements, as light cannot pass through these thicknesses. For the 20nm film, both reflection and transmission measurements have been carried out. The samples were placed in a flow cell that can measure both electrochemistry and UV/Vis response at the same time. The flow cell was filled with sulfuric acid electrolyte, and the potential was scanned between hydride and oxide formation regimes. The result proves that hydride formation in palladium can be analyzed with a rather simple optical measurement with resolution corresponding to fractions of a monolayer, both for thicker and thinner films. The amount of hydride formed could be determined, even though the hydrogen evolution reaction interfered with the interpretation of the formed hydride. Hydrogen evolution reaction occurs below 0V (vs. RHE) and caused problems for the flow cell as bubbles formed on both the working and counter electrode. Preliminary measurements were also performed on platinum thin-films with a thickness of 0.5 and 1.5 nm. This showed promising results but more tests should be performed so that good conclusions can be made. The main conclusion is that combining electrochemistry and optical techniques is a powerful tool that can give more understanding of the reactions taking place in, and on, materials used in fuel cell and hydrogen storage research. Optimizing the setup can lead to great new discoveries, driving the hydrogen economy even closer to realization.
Beskrivning
Ämne/nyckelord
Energi , Grundläggande vetenskaper , Hållbar utveckling , Fysik , Energy , Basic Sciences , Sustainable Development , Physical Sciences