| Author: | Xu, Dan |
| Title: | The investigation of advanced carbon-based nanocomposites for renewable energy application |
| Advisors: | Lu, Lin (BEEE) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Nanostructured materials Carbon Renewable energy sources Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Building Environment and Energy Engineering |
| Pages: | xviii, 189 pages : color illustrations |
| Language: | English |
| Abstract: | Nanotechnology has been used in various emerging renewable energy applications, and the focus is to enhance the efficiency of existing technologies. While the challenges of nanomaterials in practical applications include the cost, the stability and sustainability, and environmental impact. The strategies for developing new carbon nanomaterials typically involve structural design and functional enhancement. This thesis explores new strategies for advanced carbon nanocomposites, enhancing the performance in hydrogen generation, photothermal utilization for water production and nano-mechanical harvesting. First, to develop efficient electrode for hydrogen production through water electrolysis, 3-D composites has been synthesized by using laser-induced forward transfer (LIFT) technology. The study introduced a facile method to fabricate a composite consisting of ultrasmall CuxO nanoparticles immobilized on porous graphene dispersed on Ni foam. This composite demonstrated remarkable performance in the hydrogen evolution reaction (HER) when tested in a 1M KOH solution. It exhibited a low overpotential of 149.6 mV to achieve an area current density of 10 mA cm-2, with a Tafel slope of 157 mV dec-1. This study highlights the promising potential of the proposed facile preparation method, offering a highly efficient and cost-effective catalyst for scalable hydrogen production. Second, utilizing LIFT technology combined with solar driven evaporation technology, a composite of Cu nanoparticles (Cu NPs) and Graphene has been synthesized to achieve solar driven freshwater harvesting. A portable interfacial evaporator was fabricated using a one-step deposition method, employing a 3D-structured plasmonic enhanced photothermal nanocomposite composed of Cu nanoparticles/laser-induced graphene (Cu NPs/LIG). This innovative evaporator demonstrates excellent solar absorption with broadband spectrum coverage. Furthermore, this solar-driven evaporator exhibits a high evaporation rate of 2.29 kg/m2·h when operating with pure water. Long-term experiments showed a high evaporation efficiency of 1.82 kg/m2·h when operating with brine containing a high salinity of 20 wt.%. Third, interfaces have been built through the incorporation of polarizable molecules into single-walled carbon nanotubes to harness energy through the flexoelectric effect. Semiconductor single-walled carbon nanotubes (SWCNTs) with diameters ranging from 1.0 nm to 1.5 nm were carefully chosen for the study. Within these SWCNTs, two distinct types of polar molecules were embedded. The flexoelectric effect in these modified carbon nanotubes, initially non-polarized, was examined using the atomic force microscopy (AFM) probe technique. By combining AFM scans in orca, PFM, SCM, and AM-FM modes, this engineered interface enhancement strategy was validated and visualized from both electrical and nanomechanical imaging perspectives. In summary, this thesis has newly developed strategies for obtaining advanced carbon nanocomposites. The laser fabricated novel composites have been successfully applied for hydrogen production and solar-driven vapor generation. Meanwhile, the functionalization strategy of surfaced modified SWCNTs by two polar molecules has been first time studied to construct engineered interface, and nano energy harvesting has been successfully achieved via the flexoelectric effect. The strategies employed in this thesis for the facile fabrication of 3D graphene-based nanocomposites and interface engineering have laid the foundation for developing novel functionalized carbon nanomaterials. These strategies have also expanded the utilization of new carbon nanomaterials in renewable energy applications. |
| Rights: | All rights reserved |
| Access: | open access |
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