High-spatial-resolution mapping of catalytic reactions on a single nanoparticle scale

Shahar Dery, Chemistry, HUJI, Jerusalem, Israel (Shahar.dery@mail.huji.ac.il)

The catalytic activity of heterogeneous catalysts strongly depends on the spatial distribution of surface active sites such as atomic steps and surface defects. However, detection of these active sites at the nanoscale cannot be easily achieved and often done indirectly by ensemble-based spectroscopic measurements. Recently, it was demonstrated that the various active sites on the surface of single nanoparticle can be detected using high spatial resolution IR nanospectroscopy measurements^1,2. This novel approach provided the capabilities to overcome the diffraction limit of light and obtain IR measurements with 20 nm spatial resolution. In these measurements we used N-heterocyclic carbene molecules, which were surface-anchored to Pt and Au nanoparticles as chemical markers to identify catalytic reactions on the surface of a single metallic nanoparticle. Synchrotron-based IR nanospectroscopy (SINS) measurements mapped the chemical changes on the surface of nanoparticles following their exposure to various oxidizing and reducing conditions. The perimeter of the nanoparticles was found to be more active than the relatively flat center, affirming the well-known correlation between low-coordination number atoms and enhanced catalytic reactivity. In addition, ensemble-based infrared reflection-absorption spectroscopy (IRRAS) measurements provided valuable far-field information which was correlated with the IR nanospectroscopy measurements. This study offers a new way for probing and understanding heterogeneous catalysts in the nanoscale.

 

 

[1] C. Y. Wu, W. J. Wolf, Y. Levartovsky, H. A. Bechtel, M. C. Martin, F. D. Toste and E. Gross, Nature, 2017, 541, 511–515

[2] S. Dery, S. Kim, D. Haddad, A. Verdini, A. Cossaro, L. Floreano, F. D. Toste and E. Gross, Chem. Sci., 2018, 9, 6523–6531