Oxygen on the top of the smallest mountain

 Due to the corrugation of graphene and the electronic structure of matter on the sub-nanometer scale, oxygen only adsorbs on top of very small size-selected Pt clusters


F. Loi et al., Small Structuresn 2400250, (2024)

Oxygen on Pt13
The field of catalysis has long been intrigued by understanding the type and the properties of adsorption sites of atoms and molecules on solid surfaces with the final and major question: what is the most “active sites” for a specific chemical reaction? While distinguishing adsorption sites on single crystal surfaces and nanoparticles has become routine with several experimental techniques, understanding the positioning of atoms and molecules on nanoclusters poses a significant challenge due to the absence of crystalline order (diffraction based techniques cannot be employed) and the large variety of non-equivalent local atomic configurations (the spectroscopic information are not clear cut).
Motivated by the significant interest in Pt-based catalysts, as evidenced by several seminal studies such as those by S. Vajda et al. (Nature Materials 8, 213 (2009)) and L. De Rita et al. (JACS 18, 746 (2019)), we have investigated the dissociative molecular adsorption process of oxygen on ultrasmall Pt clusters supported by graphene. This process holds a great importance in the field of heterogeneous catalysis. Thanks to the unique sensitivity of the High-resolution core level photoelectron spectrocopy and our new approach to the problem we reveal that oxygen preferentially binds to the topmost atomic layer of Pt12 and Pt13 clusters, which are widely studied for their unique properties. We attribute these outcomes to the unexpected pinning process of the graphene layer on which the Pt clusters are deposited, and to the non-uniform and layer-dependent electronic charge redistribution within the clusters.
 






 

Our results highlight the significant differences in the electronic properties of atoms belonging to a portion of subnanometric matter, a feature that profoundly influences their behavior during the initial stages of a chemical reaction, such as the dissociative molecular adsorption process.
Our achievements shed new light on the concept of preferential adsorption sites, which is extensively studied in surface and interface science and assumes an even greater importance in the case of nanoclusters, i.e. in the zero-dimensional limit.

Retrieve article
Unveiling Inequality of Atoms in Ultrasmall Pt Clusters: Oxygen Adsorption Limited to the Uppermost Atomic Layer

Federico Loi, Luca Bignardi, Deborah Perco, Andrea Berti, Paolo Lacovig, Silvano Lizzit, Aras Kartouzian, Ueli Heiz, Dario Alfè  and Alessandro Baraldi

Small Structures 2400250 (2024) 















 
   
Last Updated on Saturday, 19 October 2024 19:06