In Operando Characterization of Cutting Edge Fuel Cells Catalysts Using X-Ray Absorption Spectroscopy: Capabilities of the XAFS Beamline at Synchrotron Elettra (Trieste, Italy)

In a world with a growing population, the demand for energy is rising as never before and we are aware that fossil fuels are not the solution due to their enormous environmental costs (such as the effects of climate change) that can only be thwarted in a low-carbon society. In this context, the role of batteries and fuel cells in everyday life is undeniable, and tremendous efforts are made to optimize their performances. The knowledge of the relationship between the electrochemical processes and the chemical and morphological changes is a necessary step for such optimization. An inevitable ingredient of this research are the experiments conducted in operando conditions, very useful for the study of the local chemical environment of electrode materials (electrodes, electrolytes and catalysts). In fact, in operando experiments, the collected data provide an accurate representation of the reaction behavior found under normal operating conditions and with realistic gaseous or liquid environments. Moreover, experiments conducted with this method allow to prevent several drawbacks due to the sample transfer needed for typical ex situ measurements. Alteration of air or moisture sensitive species is avoided, as well as the occurrence of relaxation reactions which might show up when the electrical circuit is open, inducing a transformation of the initial cycled material. The whole study can be performed on a single test cell suppressing the effects of uncontrolled differences in a set of cells which are needed for a stepwise ex situ study of the electrochemical mechanism. X-ray absorption spectroscopy is a synchrotron radiation based technique that is able to provide information on both local structure and electronic properties in a chemically selective manner. It can be used to characterize the dynamic processes that govern the electrochemical reactions, and to shed light on the redox chemistry and changes in structure to design efficient materials with improved properties. The XAFS beamline at Elettra is dedicated to X-ray absorption spectroscopy and can operate in a large energy range (from 2.4 to 25 keV). Although conceived to be general purpose, recently a lot of research has concerned the operando study of state of the art fuel cells and batteries. In this presentation, the XAFS beamline at synchrotron Elettra will be described together with the experiments conducted in operando conditions on proton-exchange membrane fuel cells (PEMFCs) in the context of the CERIC Grant Research proposal “CEROP”, aimed at deciphering single-atom catalysis in Pt/ceria systems. Moreover, improvements recently implemented at the XAFS beamline to perform this type of measurements will be shown.