Electricity-driven water splitting reaction achieved by electrochemical method to produce hydrogen and oxygen is utilized as an energy carrier in the form of highly pure hydrogen gas. However, the development of earth-abundant, durable, and highly effective electrocatlyst to overcome the high overpotentials of hydrogen, and oxygen evolution reaction (HER, OER) is extremely challenging. This dissertation presents firstly the catalytic properties of tungsten disulfide (WS2) as highly effective HER catalyst through direct growth of 2H-WS2 layered materials on a conductive substrate. Effect of various gaseous atmosphere and temperatures was studied and it was found that the amorphous structure of WS2 can be strongly affected under H2S environment which leads to the formation of bridging disulfide ligands S2 2- and apical S2- from WS3 phase, which is consequently contribute to the catalytic enhancement toward HER with extremely low overpotential (η10 = 184 mV).
On the other hand, OER is the major bottleneck in water splitting reaction due to its poor kinetics originated from the complex four electrons transfer process. Chemical vapor deposition strategy is used here to enable stoichiometric tuning and phase engineering of CoP2 OER electrocatalyst followed by deposition of carbonaceous protection layer to overcome surface oxidation.
Electrochemical studies indicate that C@CoP2/CC can achieve a remarkable activity (η10 = 234 mV), with minor decay from its initial current density after continuous operation of 80 hours. Lastly, electrolysis of alkaline water is the most common industrial method to produce H2; however, it is a formidable challenging to compete with Pt catalyst in base at industrial scale. For that, temperature-dependent phase evolution was studied in details and it is found that (Co(OH)2) precursor undergoes phase transition under a unique phosphidation system starting with partially phosphatized phase CoP-CoxOy, followed by phosphorus rich phase CoP2, and ultimately to pure CoP phase under elevated temperatures. Comprehensive analysis revealed that concerted composite CoP-CoxOy is the most active phase to produce H2 electrochemically from alkaline water which is contributed to the unique role of integrated phase and its ability to overcome the sluggish hydrogen kinetics in base.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/675043 |
| Date | 05 1900 |
| Creators | Alsabban, Merfat |
| Contributors | Han, Yu, Physical Science and Engineering (PSE) Division, Huang, Kuo-Wei, Tung, Vincent, Lai, Zhiping, Li, Lain-Jong |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2023-01-19, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2023-01-19. |
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