Research projects

Hydrogen in the best fuel choice to replace fossil fuels, both from the perspective ofenergy content and environmental impact. The aim of this Project is to research viable solutions for solar energy harvesting and its conversion in hydrogen, taking advantage of the extraordinary catalytic properties of the atomic quantum clusters (AQCs) of metal elements. AQCs consist in groups of metal atoms of well-defined compositions and with one or few stable geometrical structures. AQCs show discrete energy levels and similar behaviour as semiconducting materials (TiO2, ZnO…). Due to this fact, AQCs show important photocatalytic activities and we studied in this Project the use of AQCs for developing efficient systems for solar energy harvesting and its conversion in hydrogen.

At the end of 2018 we proved that when Cu₅ clusters are deposited on TiO₂ nanoparticles it is possible to extend the absorption of the photoactive material to the visible region. This fact has allowed us to focus on the search of suitable substrates for the clusters deposition and to find the better conditions for the fabrication of photocatalysts with absorption in the visible range. We researched the best conditions for the deposition of photochemically-synthesized Ag₅ clusters on ZnO nanoparticles. These hybrid AQCs/semiconductor materials have shown higher efficiency on the photocatalytic degradation of dyes, both in the ultraviolet and visible regions.

Regarding hydrogen photoproduction, we selected a suitable hole scavenger for the trials and several experiments with and without metallic nanoparticles were performed, both in the near ultraviolet and in the visible regions (using a solar simulator). We also confirmed that metal nanoparticles are not needed to support the AQCs for the hydrogen photoproduction, simplifying the preparation of the AQC-based photocatalysts. We confirmed that it is possible to achieve the photoproduction of hydrogen, which is much higher than TiO₂ without clusters, using a solar simulator with very small loading of Cu₅ AQCs. This production can be boosted by increasing the concentration of Cu₅ AQCs and the surface area of the TiO₂ NPs.