Options
Photocatalytic processes for sustainable hydrogen production from renewable sources
Gombac, Valentina
2012-04-17
Abstract
The importance of hydrogen as an appealing energy vector, due to its high efficiency and environment-friendly use in Fuel Cells, is nowadays well recognized and documented. Nevertheless, in spite of several research activities in this field, the large-scale production of H2 is still a challenging issue in view of the possible transition to an H2-based economy. In this context, the development of materials capable of acting as multi-functional platforms for the sustainable generation, though representing a strategic target, is still far from being completely satisfied. In order to make feasible the dream of utilizing sunlight for sustainable energy production, it is of paramount importance to develop catalytic systems that are not affected by leaching or poisoning phenomena and possess a high photonic efficiency, in particular upon visible activation. Heterogeneous catalysis is a key area that can help solving this issue. Using the tools offered by nanotechnology, the tailored preparation of nanoarchitectures can lead to the obtainment of photocatalytic materials that show remarkably better performance than that currently achievable even with state-of-the-art materials. The main focus of this thesis is the preparation of such tailored photoactive materials and their characterization in order to obtain catalysts that are active and stable for the sustainable photocatalytic hydrogen production by photoreforming of biomass derived compounds as raw materials.
Different synthetic approaches are developed in this work to achieve the above mentioned scopes. The materials were prepared either in the form of nanopowders with controlled morphology or of supported nanostructures. Embedding approach, in which preformed metal nanoparticles are encapsulated in porous titania, and photodeposition of metal nanoparticles over preformed tailored supporting titania were investigated for nanopowder materials. Different oxide-based materials were synthesized by Chemical Vapor Deposition (CVD) and Plasma enhanced-CVD for the supported systems. The CVD route is compatible with large-scale production, to prepare metal oxide nanostructures on Si (100), enabling the resulting metal oxide phase composition and nanoscale organization to be controlled by simple variation of the growth temperature. In addition, and more interestingly, the photocatalytic production of hydrogen on the supported catalysts upon irradiation with UV and even visible light proved that the control of the system morphogenesis is crucial to obtain good performances even in the absence of TiO2.
The results obtained represent an important step forward in the exploration of new active nanosystems for the conversion of solar light into storable chemical energy. All the findings significantly contributed to the development of photocatalytic materials for hydrogen production.
Insegnamento
Publisher
Università degli studi di Trieste
Languages
en
File(s)