Abstract
We present a systematic study on the adsorption properties of molecular oxygen on Pt, Ni and PtNi clusters previously deposited on MgO(100) by means of density functional theory calculations. We map the different adsorption sites for a variety of cluster geometries, including icosahedra, decahedra, truncated octahedra and cuboctahedra, in the size range between 25–58 atoms. The average adsorption energy depends on the chemical composition, varying from 2 eV for pure Ni, 1.07 for pure Pt and 1.09 for a Pt s h e l l Ni c o r e nanoalloy. To correlate the adsorption map to the adsorption properties, we opt for a geometrical descriptor based on the metallic coordination up to the second coordination shell. We find an almost linear relationship between the second coordination shell and adsorption energy, with low coordination sites, such as those located at the (111)/(111) and (111)/(100) cluster edges-displaying adsorption energies above 1 eV, while higher coordination sites such as (111) cluster facets have an interaction of 0.4 eV or lower. The inclusion of van der Waals corrections leads to an overall increase of the O 2 adsorption energy without an alteration of the general adsorption trends.
Highlights
The development of novel mobility technologies for cleaner vehicle emissions is nowadays essential in order to mitigate the current high levels of pollution seen on internal combustion engines
Five different O2 adsorption sites are considered for those supported PtNi clusters involving truncated octahedral (TO) and CO geometries: (1) “along edge(111)/(111)”; (2) “along edge(111)/(100)”; (3) “between edge (111)/(100)” as well as (4) “FCC” and (5) “HCP” sites
For supported PtNi clusters, the strongest calculated Eads values for TO and CO configurations are located along the cluster edges
Summary
The development of novel mobility technologies for cleaner vehicle emissions is nowadays essential in order to mitigate the current high levels of pollution seen on internal combustion engines. FCs are generally classified according to the type of electrolyte used, and excellent technology reviews exist on the literature, ranging from proton-conducting metal–organic frameworks [2], crystalline porous-materials [3], as well as carbon- and nitrogen-based porous solids [4]. Among all of the existing fuel cells, the proton exchange membrane fuel cell (PEMFC) has been actively developed for use in vehicles [5,6]. Its mass commercialization is currently hindered both by the slow oxygen reduction reaction (ORR) at the cathode and the extremely high cost of platinum (Pt). This has triggered an active search for cheaper
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