Producción fotocatalítica de h2 con microrreactores y cristales fotónicos

• Autores: Alejandra Castedo Rodríguez
• Directores de la Tesis: Jordi Llorca Piqué (dir. tes.), Lluís Soler Turu (dir. tes.)
• Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2018
• Idioma: español
• Tribunal Calificador de la Tesis: Luis María Gandía Pascual (presid.), Montserrat Perez Moya (secret.), Francesc Medina Cabello (voc.)
• Programa de doctorado: Programa de Doctorado en Ingeniería Nuclear y de las Radiaciones Ionizantes por la Universidad Politécnica de Catalunya
• Materias:
  • Física
    • Química física
      • Catálisis
    • Física del estado sólido
  • Química
    • Química inorgánica
      • Hidrogeno
  • Ciencias tecnológicas
    • Ingeniería y tecnología químicas
      • Tecnología de catálisis
• Enlaces
  • Tesis en acceso abierto en: TDX
• Resumen

  • The depletion of fossil fuels and increase of global warming lead to a high demand for alternative energy sources that should be cheap and renewable to fulfill the future energy demand. The photocatalytic generation of H2 from renewable and abundant substrates under direct solar radiation has attracted a special interest in recent years. This work deals with the design and manufacture of silicone (PDMS) microreactors that are transparent to incoming solar radiation and functionalized with a Au/TiO2 photocatalyst for the photocatalytic generation of H2 from water and/or ethanol or bioethanol gaseous mixtures under UVA and direct solar irradiance. We have shown that a simple and cheap procedure based on 3D printing can be exploited for developing silicone microreactor designs, which represent an attractive and customizable solution for conducting photochemical reactions to produce H2 at low cost.Taking into account the obtained results in the experiments using silicone microreactors and with the purpose of carrying out its scaling-up, a kinetic model that accurately describes the process has been developed, considering that H2 is produced through the photocatalytic dehydrogenation of ethanol. This equation incorporates an apparent rate constant (kapp) that has been found to be proportional to intrinsic kinetic rate constant (k), and that depends on the light intensity (I) as follows: kapp = kI0.65. Indeed, the model adequately describes the H2 production of both the single and triple stack configuration of silicon microreactors, suggesting that the scale-up of this technology through numbering-up could be relatively straightforward.Despite the photocatalytic H2 generation is not a thermal process, a few previous studies have shown the influence of temperature on these processes, although this is not fully understood. For this reason, in this work the effect of temperature from 298 to 348 K has been studied on the photocatalytic H2 generation from water:ethanol gaseous mixtures under UVA irradiation, using a silicone microreactor functionalized with Au/TiO2 photocatalyst. The obtained results demonstrate that an increase of the reaction temperature favors the generation of H2, however, it has been observed that this trend is not linear. Following the same idea, it has been evaluated whether sunlight could lead to feasible production of solar H2, carrying out the reaction under direct solar radiation.Regarding the photocatalyst, the idea of developing photonic structures that allow the manipulation of light is one of the most promising current strategies to improve its efficiency. In this thesis, the use of photonic crystals based on inverse opals of TiO2 (TiO2 IOs) as photocatalysts has been proposed, since in this type of structures occurs a phenomenon named “slow photon effect”, which is characterized by the decrease in the velocity of propagation of photons inside the material (TiO2). To test the activities of these structures, a photocatalytic device has been developed using a CNC machining technology. The results have shown that the TiO2 IOs structures result in higher H2 production rates than those obtained employing the TiO2 catalyst without photonic structure. Au/TiO2 IOs systems have led to a larger photocatalytic activity under UV-visible radiation through the synergistic action of the slow photon effect that occurs over the photonic structure of TiO2 IOs and the SPR effect that occurs over the Au NPs.