Electrocatalysis for the reduction of organic nitroarenes and inorganic nitrite

Stergiou, Athanasios (2022) Electrocatalysis for the reduction of organic nitroarenes and inorganic nitrite. PhD thesis, University of Glasgow.

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Electrochemistry is an emerging field in the physical sciences, covering a range of processes in a variety of areas. Whilst electrochemistry has been established in applications such as wastewater treatment and fuel production, there is a lot of room for growth in other fields. With the ever-increasing necessity of developing «green» processes to replace the traditional, non-environmentally friendly methods, electrocatalysis rises as a potential solution in many cases. The purpose of the work carried out in this thesis was to develop and examine electrocatalytic processes for the reduction of organic and inorganic substrates.

In Chapter 1, we discuss the use of redox mediators in the concept of organic electrosynthesis and decoupled electrolysis. More specifically, we comprehensively cover the use of polyoxometalates as redox mediators in organic electrosynthesis as well as providing examples of decoupled processes involving organic substrates. We also discuss the use of Vanadium in decoupled water electrolysis, as it has been identified as a potentially effective redox mediator for organic electrosynthesis due to its redox chemistry. In Chapter 2, we cover the theory behind the techniques that are used throughout this thesis. With the theoretical background and recent advances in the field covered in Chapters 1 & 2, we then start the discussion of our experimental work, covered in Chapters 3-5.

In Chapter 3, the development of a novel electrochemical process for the synthesis of various anilines, through the reduction of their corresponding nitrobenzenes, is discussed. By using phosphotungstic acid as the redox mediator (electro-catalyst) and controlling the applied potential in the electrochemical cell, we were able to provide a highly selective and clean electro-synthetic process. Our electrocatalytic route works in aqueous solution, at room temperature and pressure, where the electrons and protons required to reduce the nitrobenzenes are obtained from water. In Chapter 4, the scope of the process developed in Chapter 3 is massively expanded. Phosphotungstic acid mediated reduction of a variety of substituted nitroarenes, including potentially competing reducible groups and substrates that are difficult to reduce selectively by other means, was successfully performed. The performance of this method in terms of starting material conversion and product selectivity was also compared to the direct reduction at the electrode surface. In Chapter 5, we discuss our preliminary studies for the development of an electrocatalytic process for the selective multi-electron reduction of nitrite using iron porphyrins as electro-catalysts. Finally, we investigate the role of PCET in the catalytic process which we believe is crucial for the catalytic efficiency of the electrochemical process.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: Q Science > QD Chemistry
Colleges/Schools: College of Science and Engineering > School of Chemistry
Supervisor's Name: Symes, Professor Mark
Date of Award: 2022
Depositing User: Theses Team
Unique ID: glathesis:2022-83331
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 22 Dec 2022 13:38
Last Modified: 22 Dec 2022 14:01
Thesis DOI: 10.5525/gla.thesis.83331
URI: https://theses.gla.ac.uk/id/eprint/83331
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