Synthesis and functionalization of metal oxide nanostructures for photoelectrochemical energy conversion

This thesis has the aim to develop new nanomaterials based on ceramic metal oxide semiconductors for energy applications. The synthesized materials were used for the assembly of electrodes to be used in the photoelectrochemical water-splitting reaction. TiO2-anatase nanofibers were prepared by sol-gel reaction, employing nano-porous membranes as template. ZnO nanofibers, were instead prepared through electrochemical deposition on ITO transparent electrodes, or alternatively, on ensembles of gold nanowires. In the former substrate, linear nanofibers were obtained, in the latter, hierarchically branched fibers were obtained. Branched nanofibers have proven to be the most efficient among those summarized in this thesis, and have demonstrated efficiencies 7 times higher than that of conventional TiO2 nanoparticle electrodes. In the last part of the thesis, we studied the asymmetric functionalization of microfibers by bipolar electrochemistry. This technique has been used successfully in asymmetric deposition of metals and conducting polymers on conductors and semiconductors microfibers. In the latter case, has been demonstrated that the electrochemical deposition, can be modulated by UV irradiation.