Premi UAB de la Fundació Autònoma Solidària (FAS) als millors Treballs de Fi de Grau sobre desenvolupament sostenible i justícia global. 1a Edició, curs 2016/2017Hydrogen gas is regarded as the next generation green fuel. Nevertheless, its production presents several drawbacks such as CO2 emission from natural gas steam reforming, its actual main mode of generation. For that reason is critical to achieve an alternative and environmental friendly path for its mass production.Water splitting is meant to be the answer to the problem. It uses water, an inexhaustible raw material, for the generation of H2 and O2. The energy for the redox reaction can be supplied from manifold sources, although the object of study of the present report is to focus on photocatalytic water splitting since it uses sunlight as the ultimate source of energy. Photocatalytic water splitting uses a photosensitizer to convert solar energy into chemical energy, meaning that upon irradiation, electron excitation and transferral arise. In the hydrogen evolution reaction (HER), also called proton reduction, the reduction semi-reaction of water splitting, the catalyst captures the electrons withdrawn from the photosensitizer, which are previously provided from the oxidation semi-reaction of water to dioxygen, to reduce protons into dihydrogen. It is of great interest to develop efficient (low onset overpotential), active (high TOF) and robust (high TON) non-toxic catalysts for both the water oxidation and the proton reduction reactions. The present report focus on the photocatalytic proton reduction semi-reaction by using a concrete set of ruthenium nanoparticles as catalysts and the posterior optimization of the photocatalytic system employed. The first photocatalytic studied system consists of a photosensitizer, an electron mediator, a catalyst (Ru NPs) and sacrificial electron species. Photocatalytic systems are highly complex. Additionally, one sole research group has been working with systems similar to those treated in the present report. In order to achieve measurable hydrogen responses these systems need a lot of optimization. The incapability of our systems to provide reasonable hydrogen signals was thought to lie in the poor interaction between the systems' components (low electron transfer rates). An alternative to the first photocatalytic system consists in ruthenium nanoparticles deposited onto graphene oxide quantum dots (GQDs) hybrid materials embedded onto the surface of a major photoactive N-TiO2 matrix forming a cake-like system (Ru@GQDs@N-TiO2), where the GQDs are acting as a linking-conductive-intermediate enhancing the interaction between components. For that purpose, ruthenium nanoparticles were impregnated and [Ru(cod)(cot)] decomposed onto graphene oxide quantum dots in order to obtain the hybrid material (Ru@GQDs)
