Francois Rochet1

1, LCPMR Université Pierre et Marie Curie, Paris, , France

Interfaces are places where the chemical bond is deeply affected. The result is an unprecedented chemical reactivity and a modification of the electronic properties (charge transfer, appearance of an electric field), which can give rise to various technological applications (electronic devices, photocatalysts, inverse catalysts, photovoltaic devices, etc.). In this context, photoelectron spectroscopies provide essential information at the nanoscale, on atomic environment of atoms and on the energetic positioning of electronic levels, at surfaces, interfaces between dissimilar materials, interfaces between phases (e.g. gas/solid ). A renewal of these spectroscopies is now possible thanks to real time, in situ techniques, epitomized by near ambient pressure XPS (NAP-XPS) using synchrotron radiation. We will take examples from recent experiences performed by our group. We will show how it can be applied to catalytic problems (such as CO oxidation), and we will highlight the wealth of information it provides, but we will also discuss its possible limitations. In the field of aqueous solution surface chemistry we will examine the interesting questions NAP-XPS can tackle, with potential relationship with fields of chemistry such electrochemistry. Finally, we will address the issues related to X-ray beam induced radiolytic effects, which are particularly sensitive for systems in which water is confined. We will examine specifically the case of layered minerals (such as clays), and we will see how a serious concern can transform into a new field of investigation for real-time XPS.