HETEROGENEOUS CATALYSIS FOR THE PRODUCTION OF HYDROGEN VIA WATER SPLITTING

Humans are facing a food, water and energy crisis mostly due to an increase in global energy demand, escalation in world population, and continued dependence on fossil-based fuels for energy generation and transportation. If serious environmental problems wants to be avoided, clean and renewables sources of energies have to be developed and employed. Hydrogen has been proposed as one alternative to the use of traditional fuels. However, most of the hydrogen that is produced worldwide comes from non-renewable sources, polluting the environment in the process. The use of catalysts, such as TiO₂ and ZnO, has gained a lot of attention due to the potential to produce hydrogen via water splitting by using the radiation that comes from the sun. Yet, the use of these systems are facing a lot of challenges mainly to the low conversions efficiency caused by the recombination of electron-hole pairs. For these reasons the objectives of this investigation were: a) Synthesize high surface area catalysts (TiO₂NWs and ZnONPs), 2) Incorporate gold nanoparticles to the as-synthesized catalysts and on their commercial forms, and 3) Study the production of hydrogen via water splitting of the modified catalysts. The hypotheses of the study were: a) The catalyst with the higher surface area will produce the highest amount of hydrogen, and b) The gold nanoparticles will enhance the hydrogen production and will allow the use of visible light due to the surface plasmon resonance of the gold nanoparticles. Interestingly, the incorporation of the gold nanoparticles on the surface of all the catalysts enhanced their surface areas. The maximum hydrogen production obtained by using the titanium oxide catalysts were 800 μmolg^-1h^-1 (commercial) and 1,436 μmolg^-1h^-1 (TiO₂NWs). For zinc oxide, the maximum hydrogen production obtained by the commercial form was 559 μmolg^-1h^-1, and 709 μmolg^-1h^-1 for the ZnONPs. All the hypothesis were correct and all the objectives achieved. The contribution of this research relies in finding new and clean ways to produce energy from renewable sources.