Modeling and production of metal nanoparticles through laser ablation and applications to photocatalytic water oxidation

The contents of the present thesis can be divided into three parts. The first three chapters introduce the general context in which this work was developed: the social impact, the motivations and the key concepts of our research field. In particular, in Chapter 1 we discuss about the energy issue, focusing on the problem of sustainability of the energy sources. Through an analysis of updated energy and population statistics, we come to the conclusion that solar energy is the most environmentally, economically and socially sustainable energy source. Then, in Chapter 2 we present the basics of photoelectrochemical water splitting, as a possible strategy of solar hydrogen production. This discussion is inserted in the more general topic of artificial photosynthesis toward solar fuel generation. In view of the experimental work presented in this thesis, we put attention on semiconductor-based photoelectrochemical water splitting and on heterogeneous catalysis with inorganic catalytic materials. More specifically, we propose physical vapor deposition techniques as synthetic methods suitable for the industrial production of thin films for photoelectrochemical applications. In Chapter 3 we introduce the fundamentals of physical vapor deposition techniques (namely, radiofrequency magnetron sputtering, electron-beam deposition and pulsed laser deposition). The second part highlights some fundamental mechanisms that are relevant in the pulsed laser ablation of metals. In particular, we review our recent results on the modeling of liquid nanodroplet formation in the nanosecond laser ablation of pure metals. Chapter 4 develops a simplified model of phase explosion, based on the theory of homogeneous boiling. Through a continuum approach, we describe the liquid nanoparticle formation in a metastable liquid metal, whose temperature is constant over time and space. The results of our computational simulations are presented here for a set of seven metals (Al, Fe, Co, Ni, Cu, Ag and Au), commonly used in pulsed laser deposition. ...