“Catalysis, is a strange principle of chemistry which works in ways more mysterious than almost any other of the many curious phenomena of science” New York Times: June 8, 1923
Heterogeneous catalysis is one of the most extensively studied functional systems since it is in the heart of chemical industry, fuel, energy production and storage and also is part in the devices for environmental protection.
The key processes in heterogeneous catalysis occur at dynamic reactant/catalyst surface interfaces. Since these processes involve coupling between different electronic, structural and mass transport events at time scales from fs to days, and space scales from nm to mm, we are still far from full comprehension how to design and control the catalysts performance. In this respect the ultrabright and tunable light, generated at the synchrotron facilities, has opened unique opportunities for using powerful spectroscopy, spectromicroscopy, scattering and imaging methods for exploring the morphology and chemical composition of complex catalytic systems at relevant length and time scales and correlate them to the fabrication or operating conditions.
The very demanded for catalysis studies is the surface sensitive PhotoElectron Spectroscopy (PES), based on the photoelectric effect, for which Einstein won the 1921 Nobel Prize in Physics, and demonstrated for the first time in 1957 by Kai Siegbahn who was awarded the Nobel Prize in 1981. PES has overcome its time and space limitations for studies of catalytic surface reactions thanks to the synchrotron light, which also added the opportunity for complementary use of X-ray absorption spectroscopy. At Elettra, the first time resolved PES studies with model metal catalyst systems were carried out at SuperESCA beamline in 1993 and few years later PES microscopy instruments, Scanning PhotoElelectron Microscope (SPEM) and X-ray PhotoElectron Emission Microscope (XPEEM) at ESCAMicroscopy and Nanospectroscopy beamlines have allowed for sub-mm space resolved studies, including imaging of dynamic surface mass transport processes as well.
Implementation in the last decade of operando experimental set-ups at APE, BACH and ESCAMicroscopy experimental stations for bridging the pressure gap of PES investigations has led to significant achievements in monitoring in-situ chemical, electrochemical and morphology evolution of all types catalytic systems under reaction conditions. Further complementary studies using X-ray absorption spectroscopy in photon-in/photon-out mode, ongoing at the XAFS and TwinMic beamlines are filling some remaining knowledge gaps for paving the road towards knowledge-based design and production of these complex and very desired functional materials.
M. Amati, L. Bonanni, L. Braglia, F. Genuzio, L. Gregoratti, M. Kiskinova, A. Kolmakov, A.Locatelli, E. Magnano, A. A. Matruglio, T. O. Menteş, S. Nappini, P. Torelli, P. Zeller,” Operando photoelectron emission spectroscopy and microscopy at Elettra soft X-ray beamlines: from model to real functional systems”, J. Electr. Spectr. Rel. Phenom. (2019) doi: 10.1016/j.elspec.2019.146902.
For first SUPERESCA – A. Baraldi, G. Comelli, S. Lizzit, M. Kiskinova, G. Paolucci “Real-Time X-Ray Photoelectron Spectroscopy of Surface Reactions” Surf. Sci. Reports 49, Nos. 6-8 (2003) 169.
For XPEEM A. Locatelli and M. Kiskinova “Imaging with Chemical Analysis: Adsorbed Structures Formed during Surface Chemical Reactions” A European Journal of Chemistry, 12 (2006) 8890.
Image: From model to real catalysts: structural and chemical complexity