Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | School of Fashion and Textiles | en_US |
| dc.contributor.advisor | Fei, Bin (SFT) | en_US |
| dc.creator | Ming, Yang | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14713 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Cobalt-based catalysts to boost water splitting reaction for wearable application | en_US |
| dcterms.abstract | The energy shortage caused by the consumption of fossil fuels has imposed threats to the modern society. Hydrogen as a clean energy can be generated from various sources by consuming thermal energy, solar energy, electricity. Among these energy sources, the intensive exploration of photo/electrocatalysts during the past three decades attested water splitting reaction as a promising solution. In current situations, there is urgent demand in lowering down the cost of hydrogen/oxygen production by electricity/solar energy. One solution is to substitute the noble metal catalysts by earth abundant element. Therefore, the enhancement of catalytic performance via modulating the catalysts’ intrinsic properties (e.g. electronic environment), morphologies and topologies has been continuously studied. Meanwhile, hydrogen therapy as its terminal application also attracts increasing interests. Herein, the synthesis and evaluation of cobalt-based electro/photocatalysts have been investigated. Moreover, a customized electrolyzer has been designed and constructed, based on the as-synthesized catalysts and textile substrates. | en_US |
| dcterms.abstract | Firstly, cobalt oxides at carbons derived from metal-organic frameworks (ZIF-8/ZIF-67) were prepared and modulated by post-phosphine treatment (P-CoOₓ/NCs). With the assistance of polyvinyl pyrrolidone, the resultant carbons obtained a high surface area (SBET= 645.7 m² g⁻¹) as well as mesoporous topologies after pyrolysis. Moreover, the electronic environment of cobalt-cobalt oxides protected by carbon layers was further tuned by doping phosphorus atoms. These strategies not only enhanced the catalytic performance but also facilitated the electron transfer from carbons to cobalt atoms. As a result, the constructed water splitting cell fabricated with 900P-CoOₓ/NCs required a low overpotential (89 mV and 343 mV vs. reservable hydrogen electrode respectively) to drive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at 10 mA cm⁻², a low cell voltage (1.69 V) and a high stability with only 4.7% decay after 15 hours operation in 1M KOH. | en_US |
| dcterms.abstract | Secondly, based on the disulphide bonds in wool keratin structure, cobalt sulfide content (4.76wt%) supported by nitrogen/phosphorus co-doped carbons (Co9S₈/N,P-ACs) were prepared by reduction, carbonization and activation treatments. Owing to the well-constructed pore system (SBET = 439.3 m²/g), heteroatom doping and distinctive metal electronic environment, the as-prepared catalysts required a low overpotential of 90.7 mV and 295.2 mV to drive HER and OER at 10 mA cm⁻². The as-fabricated two electrode cell system possessed a low cell voltage (1.62 V at 10 mA cm⁻²) and a high stability with 2.7% decay after 15 hours operation in 1M KOH. Meanwhile, an all-flexible and wearable device has been designed and fabricated by 3D printing technique by utilizing hydrogel separator, moisture sensitive salts. This work not only demonstrated a biomass conversion strategy, but also provided a solution for personalized water splitting device. | en_US |
| dcterms.abstract | Thirdly, a close contact core-shell Cadmium Zinc Sulfide @ NiCo layered double hydroxides cocatalyst (CZS@NiCo-LDHs) was facilely synthesized by surface modification of CZS using thioglycolic acid, followed by a hydrothermal growth of electrocatalyst. The obtained CZS@NiCo-LDHs cocatalyst exhibiting an average diameter of 105±5 nm with a firm LDHs shell thickness of 24 nm was obtained. Such close contact core-shell structure illustrated a hierarchical topology (SBET= 87.69 m²/g), resulting in easy diffusion of electrolyte, rapid electron-hole separation and efficient transfer of photogenerated electrons. In addition, NiCo-LDHs, as typical water splitting electrocatalysts (η10 for HER = 185 mV in 0.1M Na₂SO₄), received the excited electrons. Meanwhile, the metal ions in LDHs functioned as active sites. The high coverage of LDHs on CZS, as a result, contributed to a high PHE rate of ~18.75 mmol g⁻¹ h⁻¹, and a favorable photostability in 5 cycles under visible light irradiation (300W, λ> 420 nm). Further density function theory calculations indicate an apparent redistribution of electron after introducing LDHs. Moreover, nickel sites on CZS@NiCo-LDHs are responsible for adsorption of hydrogen atoms, which provide cocatalyst with enhanced PHE activity. | en_US |
| dcterms.abstract | In conclusion, this thesis not only explored cobalt-based photo/electrocatalyst by the strategies of protective shell design, hetero atom doping, morphology control and heterojunction construction, but also prepared one flexible customized electrochemical cell. These designing principles have shown significant improvement in catalytic performance and stability, which explore potential industrial applications. Hence, this work based on the synthesis of cobalt-based catalysts and its optimizing strategy paved new ways to design highly efficient electro/photocatalysts. | en_US |
| dcterms.extent | xxvi, 214 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2024 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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