Atomic layer deposition and electrochemical characterization of TiO2 as a potential candidate for a photoanode protective layer
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Date
2024
Authors
Shine, Micheál
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Publisher
University College Cork
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Abstract
The search for alternative fuel sources has become more prevalent in recent years due to increasing energy demands as well as the detrimental effects fossil fuels have on the environment. Solar water splitting using semiconductor photoelectrochemical cells has long been viewed as a potential means of large-scale H2 production from renewable resources.
A study was carried out to test the corrosion resistance performance of thin TiO2 layers deposited by means of atomic layer deposition under oxidative conditions. Despite Silicon being considered one of the most promising semiconductors for use in photoelectrodes, its instability in aqueous solutions is one of its main limiting factors. TiO2 film (~6 nm) were deposited on the anode surface, using atomic layer deposition and plasma enhanced atomic layer deposition (ALD), to act as corrosion protection and to passivate the electrode surface along with a 5 nm Nickel over layer to act as an oxygen evolution catalyst. The longevity of these photoanodes was the main focus of this work employing the techniques of cyclic voltammetry and chronoamperometry to evaluate electrochemical performance. Electron microscopy SEM was carried out, before and after the anodes underwent electrochemical testing, to gain insight into any surface degradation and morphological changes of the TiO2 and Ni layers that may influence charge transfer and performance. Comparisons were drawn between photoanodes prepared by ALD and plasma enhanced atomic layer deposition (PE-ALD) to give a clearer picture of the limiting factors of charge carrier mobility and photoactivity. The estimated ratio of Ti3+ to Ti4+ and hence the oxygen vacancies, played an important role in the overall conduction of the device along with the % composition of impurities present due to incomplete reactions in the deposition process. This was tested by producing films with different oxygen doses during the deposition stage.
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Keywords
Photoanode
Citation
Shiner, M. 2024. Atomic layer deposition and electrochemical characterization of TiO2 as a potential candidate for a photoanode protective layer. MSc Thesis, University College Cork.