Bimetallic Pt–Pd nano-catalyst: size, shape and composition matter
| Autor: | Grégory Guisbiers, Rafael Mendoza-Perez |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Cuboctahedron Mechanical Engineering Decahedron Bioengineering 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Gibbs free energy Rhombic dodecahedron symbols.namesake Congruent melting Octahedron Mechanics of Materials Chemical physics Tetrahedron symbols General Materials Science Electrical and Electronic Engineering 0210 nano-technology Phase diagram |
| Zdroj: | Nanotechnology. 30:305702 |
| ISSN: | 1361-6528 0957-4484 |
| DOI: | 10.1088/1361-6528/ab1759 |
| Popis: | The goal of this work is to understand how the phase diagram (PHAD) of the platinum-palladium (Pt-Pd) alloy changes with size and shape and how it correlates with catalytic properties. By using nano-thermodynamics, the size and shape effects on the PHAD of Pt-Pd nanoparticles were determined theoretically. The PHAD of some nanoparticles (sphere, tetrahedron, octahedron, decahedron, cube, cuboctahedron and rhombic dodecahedron) exhibits a congruent melting point that becomes more and more pronounced when the size decreases. At the right of the congruent melting point i.e. close to the Pt-rich side, the coexistence region exhibits a contraction while an expansion is noticed at larger palladium concentrations. From the Gibbs free energy analysis, the stability of all the considered shapes has been determined versus temperature and composition. Furthermore, the surface segregation was also calculated and it is shown that the surface segregation is reversed at very small sizes. Indeed, below a critical size, Pd does not segregate anymore at the surface like it normally does for larger nanoparticles; but Pt does. The critical size range has been determined for each considered shape; and within this range Pt and Pd co-exist at the surface. Finally, the most catalytically active shapes are predicted to be the tetrahedron and the cube in agreement with the available experimental data and other theoretical results. |
| Databáze: | OpenAIRE |
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