Silicon nanowires devices in energy and environmental applications

This thesis focuses on the development of silicon nanowires (SiNWs) and their applications in the fields of thermoelectric (TE) devices, on-demand hydrogen (H2) generation, and wastewater treatment. SiNWs have been synthesized with different morphologies and compositions, leading to tunable electrical conductivity, thermal conductivity, and TE power factor. In the first part of the thesis, SiNW-based TE devices were fabricated and characterized for their TE performance. The SiNWs were synthesized with a high aspect ratio and high porosity, leading to a high surface area-to-volume ratio and lower thermal conductivity. The TE devices based on SiNWs demonstrated high TE performance, with a high Seebeck coefficient and a low thermal conductivity. The enhancement in TE performance was achieved through the optimization of SiNW dimensions and porosity, as well as the doping of the SiNWs with impurities. The results of this study suggest that SiNWs can be promising candidates for high-performance TE devices. In the second part of the thesis, the potential of SiNWs as a material for on-demand H2 generation was explored. The high surface area of the SiNWs makes them highly effective reactants for water and silicon reactions, which are crucial steps in H2 production. The unique porous structure of the SiNWs also allows for the efficient transport of reactants and products, further enhancing their H2 generation performance. The results of this study suggest that SiNWs can be a cost-effective and efficient way to produce H2, which has significant economic and environmental benefits. In the final part of the thesis, SiNWs were used as a catalyst in the field of environmental engineering for the generation of hydroxyl radicals (*OH) from hydrogen peroxide (H2O2). The combination of SiNWs with graphene oxide (GO) and Ni-doped FeOOH (Ni:FeOOH) was shown to enhance the generation of *OH from H2O2. The highly reactive *OH is well-known for its ability to efficiently and effectively degrade organic pollutants in wastewater. The unique porous structure of the SiNWs provides a large surface area for the interaction between the catalyst and H2O2, resulting in high reaction efficiency. The results of this study suggest that SiNWs can be used as a cost-effective and environmentally friendly material for wastewater treatment. Overall, this thesis demonstrates the potential of SiNWs as versatile materials for various applications in the fields of energy and environmental engineering. SiNWs have shown great promise as high-performance TE materials due to their unique physical and chemical properties. In addition, SiNWs have been shown to be effective in on-demand H2 generation and wastewater treatment, making them a promising candidate for clean energy generation and environmental remediation. Further research can be conducted to optimize the TE performance of SiNWs, explore the potential of SiNWs as a material for other energy-related applications, and investigate the use of SiNWs in other environmental remediation processes

Keywords: Engineering.
Materials Science and Engineering.
Advisor: Brongersma Mark L.
Zheng Xiaolin
Hong Guosong