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Burwell, Tom (2025) Metal-carbon nanocatalysts for electrochemical CO2 reduction. PhD thesis, University of Nottingham.

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Abstract

The work in this thesis investigates graphitised nanofibers as a support medium for metal catalysis for the electroreduction of CO2. They provide a nanotextured surface in which metal catalysts can be stabilised and the highly conductive properties of graphitised nanofibers and high surface area to volume ratio make them an ideal support for the electroreduction of CO2.

Firstly, graphitised nanofibers magnetron sputtered with Cu was tested for its electrocatalytic activity towards the CO2 reduction reaction. Using a correlative microscopy and electroanalytic approach, the catalysts properties were directly linked with in-situ morphological changes. As such the catalyst worsening properties over time was linked with changes to the catalyst itself, with emergence of single atoms of Cu and increasing nanoparticle size changing active centres and therefore selectivity.

To study another Cu magnetron sputtered catalyst in finer detail, identical location transmission electron microscopy was performed to elucidate mechanisms of catalyst reconstruction and degradation in-situ. Allowing for the Cu nanoparticles to be monitored during an accelerated CO2 reduction reaction with information gathered on not only the shape, size but the Cu-support interface. Herein, the catalysts behaviour can be monitored closely and as such the migration of Cu was found to be high on graphitised nanofibers as well as a transient mechanism of desorption of Cu and redeposition to erode Cu centres forming a thermodynamically stable catalyst. The Cusupport interface was found to be key, as the catalyst undergoes CO2 electroreduction this interface matures and forming intimate contact with the graphitised nanofiber support.The catalysts activity towards CO2 reduction was also explored, with an interesting relationship observed between the CO2 reduction reaction and hydrogen evolution reaction.

Another method for metal deposition was investigated, the electrodeposition of Sn was used to create a graphitised nanofiber coated catalyst with a unique microstructure due to the graphitised nanofibers. The catalysts activity towards the electro reduction for CO2 was evaluated and conditions optimised by increasing electrolyte concentration, in which an optimum was found. The optimum condition found was used for longterm catalysis and observed changing catalytic behaviour occurring during catalysis.

The in-situ changes of the catalyst were investigated using a correlative electron microscopy and electroanalytical approach. Revealing a known degradation mechanism to be responsible for the change in catalytic activity, but unlike previous literature examples, this improves catalytic properties over time, reaching a maximum. As such we found that the in-situ mechanism responsible for changing catalytic activity benefits this catalyst due to the nano-textured surface of the graphitised stabilising the Sn catalyst.

Lastly, to improve the catalytic activity of the electrodeposited Sn catalyst, a coelectrodeposition method was used to form a Cu/Sn bi-metallic. The co-deposition of both Cu and Sn revealed a unique morphology of the catalyst with nanostructured deposits on the graphitised nanofibers. The inclusion of Cu into the Sn catalyst was evaluated with an electroanalytical approach to evaluate the activity and formation rate of products from the CO2 reduction reaction with the previously optimised conditions for the Sn catalyst.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Khlobystov, Andrei Licence, Peter Besley, Elena
Keywords:	carbon nanofibers, nanotubes, tin nanoparticles, electrocatalysis, CO2 reduction reaction, formate production, electron microscopy
Subjects:	Q Science > QD Chemistry > QD146 Inorganic chemistry
Faculties/Schools:	UK Campuses > Faculty of Science > School of Chemistry
Item ID:	80799
Depositing User:	Burwell, Tom
Date Deposited:	30 Jul 2025 04:40
Last Modified:	30 Jul 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/80799

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