Mechanism of electrocatalytic and photo-electrocatalytic reactions by in operando X-Ray absorption spectroscopy

The purpose of my PhD research work is the investigation of the mechanism and the kinetics of electrocatalytic and photo-electrocatalytic reactions by means of in operando X-ray Absorption Spectroscopy. The attention has been focused on five electrochemical systems which can be divided into two groups on the basis of their catalytic properties. The first group essentially deals with the catalysis of the water splitting reaction: belonging to this group I firstly considered electrodes constituted of IrOx, which represents one of the major electrocatalysts in this field. Coupling IrOx electrocatalyst to a semiconductor like hematite it became possible to obtain and investigate bilayer electrodic systems for light driven water splitting. Afterward, I considered bilayer architectures composed of Ni(OH)2 and hematite, which represent cheaper and more sustainable alternatives to iridium based systems. Finally, some research work was devoted to Cu2O material, also very promising for photovoltaic applications. The experiments carried out for this materials were aimed at studying the structure and stability of one of the main precursors: copper(II) lactate in alkaline solution. The second group of electrodes plays a key role in the environmental field since comprises materials constituted of silver nanoparticles, which show great potentialities in the electrochemical de-halogenation of organic pollutants. Since the study of electrocatalytic processes involves the presence of systems in their real working conditions, adequate experimental setups and electrochemical devices were required in order to control the physic-chemical conditions of the sample. For each electrodic system the research work consisted of four steps: (i) experimental planning and construction of adequate spectro-electrochemical devices according to the subsequent experimental needs (these can be either manually-built or 3D printed); (ii) preparation of the electrodic materials (in collaboration with the University of Milan); (iii) In Situ and In Operando investigation by means of XAS Spectroscopy techniques at the ESRF (European Synchrotron Radiation Facility, Grenoble, France); and (iv) data analysis and fitting procedure.