Plasmon Enhanced Titanium Dioxide Nanotubes for Nanophotonics, Non-linear Optics, and Photocatalysis

  • Author / Creator
    Zeng, Sheng
  • Photocatalysis was originally inspired by photosynthetic models from nature, and now opens the window to a wider range of applications including but not limited to solar-to-chemical energy storage, water/air purification. Both photocatalytic hydrogen generation and CO2 to hydrocarbon processes are aiming to kill two birds with one stone by treating wastes and producing clean energy. Hydrogen has been considered as an ultimate clean energy source and is heavily relied upon for fuel cells. With that being said, so far, hydrogen has been still mainly produced from fossil fuels by steam reforming instead of photocatalytic water splitting which is a greener method. CO2 photoreduction is able to store solar energy and reduce CO2 concentration in the atmosphere simultaneously. Nature creates a balance of carbon resources in ecosystems, however anthropogenic interference destroys that balance. Photocatalytic CO2 capture is an ideal approach to close the anthropogenically opened carbon loop. This way, it rebalances the carbon emissions as in the case of photosynthesis in green plants. Largely, all my motivation comes from the urgency with global problems such as global warming and environmental pollution, which accelerate the need for greater research into photocatalysis. Thus, my efforts have been put into how to design and fabricate highly efficient photocatalysts and enhance the performance of challenging photocatalytic reactions.

    I started my first PhD project with a review paper on photocatalytic CO2 reduction using perovskite oxide nanomaterials. As the material focus of this review article, I selected perovskite oxides because they are mostly earth-abundant, nontoxic to nature, chemically stable, and tunable in many aspects such as crystal structures, bandgaps and surface energies. This review paper offers me key insights for developing advanced photocatalysts in order to improve the yields of CO2 reduction products.
    Having accomplished this review paper, I found that nanophotonics and plasmons are good angles to tackle the problem of photocatalyst with less efficiency. The idea and efforts turned into the next scientific article, entitled “optical control of selectivity of high rate CO2 photoreduction via interband-or hot electron Z-scheme reaction pathways in Au-TiO2 plasmonic photonic crystal photocatalyst”. The periodically modulated TiO2 nanotube arrays were decorated with gold nanoparticles to form plasmonic photonic crystal photocatalysts from which dramatically improved performance and remarkable selectivity are obtained.
    Admittedly, plasmonic photocatalysis promises using light as the energy source to drive a variety of thermal energy-intensive chemical reactions, however, the incorporation of plasmonic noble metals has become a double-edged sword. To overcome the drawback of relying on noble metals became the motivation of the next two manuscripts in my PhD program. The group IV transition metal nitrides have shown the possibilities as better alternatives courtesy of their unique characteristics such as exhibiting both metallic and semiconducting properties, possessing ceramic hardness, high thermal tolerance and chemical resistance. All these advantages have shown the possibility for substitution of plasmonic noble metals. These two manuscripts included in the thesis are “Femtosecond and Picosecond single pulsed laser ablation of Nonlinear Optical TiN, as alternative for gold” and “Core-Shell TiO2@HfN Nanotube Arrays: Hot Carrier Photoanode for Sunlight-Driven Water-Splitting”. They investigated the optical and material properties of TiN and proved the promising performance of HfN as photocatalyst for water-splitting.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.