Optical enhancement in water-splitting photoelectrodes: modeling and application to deposited nanoparticles

Driencourt, Luc. Optical enhancement in water-splitting photoelectrodes: modeling and application to deposited nanoparticles. 2021, Doctoral Thesis, University of Basel, Faculty of Science.


Official URL: https://edoc.unibas.ch/86186/

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Producing dihydrogen at large scale using sustainable, carbon neutral technologies is one of the main challenges facing the dual requirements of satisfying the global energy demand and minimizing the climate change. Photoelectrochemical water-splitting electrodes made with stable metal oxides have a great potential in this regard, but efficiency enhancement strategies must be found. Material nanostructuring and optical phenomena at the nanoscale such as plasmonic effects have been widely studied for improving the solar-to-hydrogen efficiency. The present thesis focuses on the theoretical and experimental understanding of such effects with an emphasis on strategies involving nanoparticle deposition which offer the advantages of being up-scalable and easy to implement. A method for analyzing the contribution of optical effects from nanostructures in enhancing the performance of photoelectrodes is described. The model involves electromagnetic simulations as well as modeling of the transport and transfer of photogenerated charges to the electrolyte. Some physical parameters can be determined by fitting the model to experimental measurements, which enable the investigation of various strategies for enhancing the performance of a fabricated electrode. This method is validated using published experimental data, and can be used to analyze experimental results and discriminate between optical and nonoptical (e.g. catalytic) enhancement. Next, improved performances obtained after nanoparticle deposition on the photoelectrode surface are investigated in detail. Bismuth vanadate, which has shown the highest reported performances as a metal oxide photoanode, is chosen as the active semiconductor material. Noble metal nanoparticles (plasmonic) are considered with different photoelectrode morphologies, for various position of the nanoparticles with respect to the active material and illumination directions. Nanoparticles of different materials are also compared. Both theoretical analysis and experiments are performed. It is found that the effects of the nanoparticles on the performances is strongly dependent on the illumination direction for a given morphology. Moreover, far-field effects are found to be predominant compared to near-field effects. Finally, an innovative strategy for enhancing the performance of water-splitting photoanodes illuminated from the electrolyte side is presented. It involves high refractive index nanoparticles such as titania. The performances of a bismuth vanadate photoelectrode are found to be enhanced by about 10% after deposition of nanoparticles. Theoretical and experimental analysis reveal that the effect originates mainly from reduced reflection losses arising from the interaction of light with the nanoparticles. Simulations with the previously described method suggest that this strategy could be applied to various photoelectrode materials where reflection losses are problematic such as iron oxide (hematite). It can potentially be used to improve further the performances of the best-performing reported devices. Compared to noble metal nanoparticles, high refractive index materials such as titania are economic and highly resistant in wide range of pH.
Advisors:Constable, Edwin Charles and Fricke, Sören and Meyer, Ernst and Haussener, Sophia
Faculties and Departments:05 Faculty of Science > Departement Chemie > Former Organization Units Chemistry > Anorganische Chemie (Constable)
UniBasel Contributors:Constable, Edwin Charles and Meyer, Ernst
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:14561
Thesis status:Complete
Number of Pages:vii,120
Identification Number:
  • urn: urn:nbn:ch:bel-bau-diss145616
edoc DOI:
Last Modified:15 Feb 2022 11:03
Deposited On:11 Jan 2022 11:37

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