Photocatalytic and photoelectrochemical systems for oxidation of aromatic compounds in an aqueous environment

• Main Author: Ng, Yun Ru
• Other Authors: Han Sen SOO
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Science::Chemistry::Physical chemistry::Electrochemistry; Science::Chemistry::Physical chemistry::Catalysis; Science::Chemistry::Physical chemistry::Photochemistry
• Online Access: https://hdl.handle.net/10356/137970
• Institution: Nanyang Technological University

As the demand for chemical products increases, alongside a rising problem of pollution due to chemical wastes, there is great interest in developing systems that can resolve either or both issues in a sustainable way. Inspired by nature, the development of photocatalytic and photoelectrochemical (PEC) systems had been pursued as a possible solution. In this work, both a PEC system involving nanoporous bismuth vanadate (BiVO4) with tetraamidomacrocyclic ligand iron complexes (Fe-TAML) as co-catalysts and a photocatalytic system involving modified graphitic carbon nitrides (g-C3N4) were investigated. Both systems were also applied to the oxidation of bisphenol compounds, as well as the oxidation of lignin in lignocellulose. In addition, a hydrophobic metal halide perovskite photocatalytic system was explored for C-C bond cleavage and dehydrogenation reactions, while tetraamidomacrocyclic ligand cobalt complexes (Co-TAML) were investigated for hydrogen evolution reaction. In Chapter 2, I present a literature review of the components of the photosystems we had worked on. These include reviews of lignocellulose and bisphenols as the substrates of interest, as well as the materials BiVO4, g-C3N4, and metal halide perovskites as viable semiconductors. The possible modifications and applications of the materials in various reactions were also investigated in this chapter. In addition, this chapter will also offer a look into the Fe-TAML co-catalysts and other TAML complexes, their origins and applications, before ending with a summary about how the proposed systems would be like. Chapter 3 follows on by describing the syntheses and characterisations of the nanoporous BiVO4 plates and the addition of Fe-TAML as co-catalysts (from hereon known as BiVO4/Fe-TAML). The PEC activities of the resulting system were shown to be promising in oxidising a selection of substrates, namely bisphenol F (BPF), bisphenol S (BPS), and lignin. Chapter 4 then describes a photocatalytic system involving a modified g-C3N4 that has both an improved surface area, as well as pyromellitic diimide (PDI) incorporated within the g-C3N4. The improvement to the photocatalytic ability of the resulting g-C3N4 was then discussed and examined, with subsequent application to the degradation of BPF. Chapter 5 summarises the collaborative projects done in exploring metal halide perovskites as a photocatalysts and Co-TAML as an electrocatalyst, with further discussions into some characterisations of the materials and catalysts involved. The thesis concludes with Chapter 6 looking into possible future work.