The increasing energy demand, necessary to meet the needs of the growing world population, has accelerated climate change in recent decades, due to the predominantly use of fossil fuels, which in addition to being pollutants are non-renewable and ill-distributed. This has aroused interest in cleaner energetic alternatives. Thus, taking Nature as an example, Artificial Photosynthesis emerges as a way to store the enormous amount of solar radiation received by the Earth, in the form of chemical bonds of a fuel. This process includes, besides the oxidation of water to dioxygen, the reduction of protons and the reduction of CO2, obtaining, respectively, dihydrogen and products derived from carbon such as methane or methanol. In both cases, the use of a catalyst is required to make the process efficient, and a photoactive material that triggers the process induced by light. Chapter I further develops the problem of climate change and the current state of the proton and CO2 reduction processes, pointing out the use of semiconductors such as carbon nitride as photoactive material and metallic nanoparticles as catalysts. In addition, the use of the organometallic method for the preparation of these catalysts is highlighted, under mild reaction conditions and with great control over their physical and chemical features. In Chapter II, the objectives of this work are exposed, centered on the design, multi-technique characterization and testing of materials based on metallic nanoparticles to carry out these processes. In Chapter III, ruthenium nanoparticles are prepared using different ligands as stabilizers, observing differences in their activity and electrocatalytic stability in the reduction of protons, related to their physical properties and composition. In Chapter IV, mesoporous graphitic nitrogen carbide (mpg-CN) is used as a photoactive material for photoinduced CO2 reduction. The effect of the loading of platinum nanoparticles to the semiconductor is tested, notably improving the efficiency and selectivity of the process. In Chapter V, mpg-CN is used again but with ruthenium and platinum nanoparticles for the photoreduction of protons. Ruthenium nanoparticles are prepared in different ways, using stabilizing ligands, carbon materials or directly deposited in the semiconductor. It is found that, regardless of the technique, the observed catalytic efficiency is similar in all these systems, and much lower than the performance of Pt. The catalytic observations are supported by photophysical studies. In Chapter VI, Pt nanoparticles supported on four different carbon materials (carbon nanohorns, carbon nanotubes, reduced graphene oxide and grahpite) are prepared and incorporated into an electroanalytical sensing platform, proving effective for the detection of parabens at ultra-trace levels. Finally, in Chapter VII the global conclusions are presented.
Ruthenium and Platinum Nanoparticles for Artificial Photosynthesis
Álvarez Prada, L. I. (Author). 1 Oct 2021
Student thesis: Doctoral thesis
Student thesis: Doctoral thesis