UC Merced

Architectures of 3D hierarchical nanostructure arrays consisting of 1D nanostructures offers a large surface area and an unobstructed electron transport pathway which are of great technological importance for energy applications. I have developed nanomanufacturing methods to consistently and reproducibly obtain 3D hierarchical architectures through the controllable synthesis of 1D zinc oxide (ZnO) and carbon nanofibers. I have demonstrated that by adjusting the catalyst properties, engineered 3D morphologies of ZnO and carbon nanofibers can be achieved on metal current collectors. Three approaches were generated to produce such hierarchical structures, using as-synthesized 1D nanostructures as scaffolds, and I have used a multi-pronged approach to functionalize these 3D surfaces. By oxidation of a few layers of outer carbon, quinone functional groups can be formed by air annealing. As a result, more than 100% enhancement in energy storage capability has been observed. I have also developed polymer electrografting techniques, both on ZnO and on carbon surfaces. Using grafted polymers as templates, a N and O co-doped carbon layer is conformably deposited on carbon nanostructures. This new carbon heterostructure leads to a greatly enhanced oxygen reduction capability. With grafted polymer as template, I have successfully generated densely populated nanoparticles on ZnO nanowire surfaces. Rationally, these nanoparticles can be then used to grow 3D branched structures. Due to the greatly enhanced surface area, I have shown that the photoactivity of ZnO is increased both as an oxidant for dyes and for photoelectrochemical systems. This set of robust nanomanufacturing protocols are transformative and can served as platforms for a myriad of application such as future environmentally conscious energy technologies