Zhang, Jichao;
(2024)
Nickel-based electrocatalysts for urea-assisted water electrolysis.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The urea oxidation reaction (UOR) has become one of the most promising routes to substitute oxygen evolution reaction (OER) with large thermodynamic potential in various energy conversion applications. Nickel (Ni)-based materials were extensively applied as suitable UOR electrocatalysts with highly active Ni3+ species that can facilitate the urea dehydrogenation process. The currently reported UOR electrocatalysts mainly focus on minimizing the overpotential to drive the reactions and revealing the reaction mechanism by comparing the physicochemical properties before and after reactions. This leads to urgent issues for undesirable electrochemical performance for industrial applications at large current densities over long-term tests and unreliable mechanism exploration. Thus, the modified Ni-based electrocatalysts were proposed in this thesis for efficient and durable UOR and structure-performance relationships were established by in situ spectroscopy observation. Specifically, chromium (Cr)-doped Ni hydroxide catalysts (Cr-Ni(OH)2) with unique wetting properties were first proposed to improve the UOR activity. The stability of Cr dopants was further probed to reveal the Cr leaching issues during the OER and UOR process. Second, to enhance the utilization efficiency of noble metal, single atomic ruthenium (Ru) sites were incorporated into the Ni hydroxide. The crucial roles of urea dehydrogenation and Ni oxidation in both low and high urea concentrations were disclosed, respectively. Zn-urea-air battery test and zero-gap membrane electrode assembly (MEA) test were conducted to validate the applicability in practical scenarios. Finally, platinum (Pt)-mediated Ni phosphide catalysts were synthesized to realize bifunctional activity for both electro-oxidation and electro-reduction, demonstrating a vision for urea-assisted water electrolysis. This thesis highlights the modification of Ni-based catalysts and reveals the reaction mechanism by in situ spectroscopic studies.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Nickel-based electrocatalysts for urea-assisted water electrolysis |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10192005 |
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