X-Ray Absorption Spectroscopic Microscopy: From the Micro- to the Nanoscale

Hard X-ray analysis has significantly contributed to the understanding of catalytic reactions. In particular, through the use of X-ray absorption spectroscopy the chemical state and local neighborhood of a chemical species involved in the catalytic reaction can be investigated, shedding light on the reaction mechanisms. As this technique does not rely on crystalline order, it can also be employed on non-crystalline solids and in the liquid phase. In addition, X-ray scattering can yield the nano structure such as the mesoscopic particle morphology in small-angle scattering and the atomic order in (poly-)crystalline samples. One key advantage of hard X-rays for studying catalytic reactions is their large penetration depth in matter that allows one to investigate the chemical state in operando, e.g., inside a chemical reactor under reaction conditions [1, 2]. It is thus also complementary to other spectroscopic techniques (e.g., micro IR, Raman, XRD, XRF), including electron microscopy (cf. for example [3, 4]).