Resumen de Design of tio2-based materials for photocatalytic environmental applications
- español
La contaminación y disponibilidad del agua y la crisis energética se han convertido en dos de los principales desafíos para la sociedad en un futuro cercano. Por lo tanto, existe una necesidad urgente de buscar tecnologías sostenibles para satisfacer las demandas de los seres humanos.
En las últimas décadas, los procesos de oxidación avanzada (POAs) han atraído un gran interés debido a su versatilidad y sus amplias áreas de aplicación. Específicamente, la fotocatálisis heterogénea ha surgido como una alternativa factible ya que permite trabajar a temperatura ambiente y presión atmosférica, siendo el dióxido de titanio (TiO2) es uno de los fotocatalizadores más prometedores debido a que es abundante y económico. Sin embargo, presenta algunos inconvenientes que dificultan su aplicación comercial.
Se hacen necesarios fotocatalizadores capaces de trabajar bajo luz visible y con bajas tasas de recombinación de los portadores de carga para la mejora de la tecnología de fotocatálisis. Con este objetivo, el óxido de grafeno y los metales nobles han sido empleados para mejorar la actividad limitada del TiO2 comercial.
Por tanto, la presente tesis doctoral tiene como objetivo el diseño, síntesis y caracterización de materiales a base de TiO2 para el tratamiento de soluciones acuosas de ácido dicloroacético (DCA) y la producción fotocatalítica de hidrógeno, un prometedor vector energético, a partir de glicerol.
- English
Increasing demand and shortage of clean water sources and growing global energy demand have become crucial issues worldwide. Human activities are currently appropriating more than 61% of the proposed planetary boundary for freshwater consumption. In addition, currently the water pollution problem cannot be solved by the natural cleansing cycle or by conventional treatments. On the other hand, 90% of the world’s energy supply is derived from fossil fuel, a limited energy source related to greenhouse effect. In this way, hydrogen is brought to the forefront as a potential energy carrier to overcome various issues related to carbon footprint. Therefore, there is urgent need to search for sustainable technologies to meet demands of human beings. Over the last decades, Advanced Oxidation Processes (AOPs) have been attracting a great interest due to their versatility and potential areas of application. Specifically, heterogeneous photocatalytic processes have appeared as a feasible alternative to conventional treatments operating at room temperature and under atmospheric pressure. This technology is defined as a reaction assisted by the presence of semiconductor photocatalyst and a potentially renewable light source. Until now, titanium dioxide (TiO2) is one of the most promising photocatalyst due to it is highly photoreactive, chemically stable and cost-effective. However, some drawbacks hinder its wider commercial application. Much effort has been devoted to the development of TiO2 visible-light harvesting photocatalysts with a low rate of charge carrier recombination. Among them, chemical modifications by incorporation of additional components in the TiO2 will be under discussion within the present thesis, applying the newly synthetized TiO2-based photocatalysts for dichloroacetic acid (DCA) remediation and hydrogen production. The first chapter presents an overview of the problems related to water scarcity and pollution and energy crisis. Furthermore, fundamentals of advanced oxidation process and specifically, heterogeneous photocatalysis are described. Special attention is invested within the chapter in highlighting the advantages and drawbacks of TiO2 as photocatalyst and the strategies employed to overcome them through improved photocatalyst design within the addition of graphene oxide and noble metals as co-catalysts. Chapter 2 collects and describes chemical reagents, experimental set-ups and procedures, characterization techniques and analytical methods employed along this work. In the third chapter, the research is focused on the optimization of high-performance photocatalysts based on graphene oxide/titanium dioxide (GO/TiO2) nanocomposites and their characterization for the effective degradation of DCA. In Chapter 4, noble metals (Ag and Pt) have been employed to improve the photocatalytic activity of TiO2 against DCA oxidation. Moreover, the role of reactive oxygen species (ROS) using these photocatalysts is examined in order to clarify the degradation pathways. With the aim of extending the area of application of TiO2-based photocatalysts, Chapter 5 collects the results of hydrogen production using synthetic and crude glycerol as feedstock and TiO2/GO/Pt ternary photocatalysts.
