Avviso di Conferenza: Alessandro Fortunelli - "Properties of Nanostructured Metals via Predictive Quantum Approaches" - Edificio C11, Aula A1 (3° piano)

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23/04/2015 - 16:30
Data fine evento: 
23/04/2015 - 17:30
Data pubblicazione evento
Pubblicato il: 
20/04/2015

 

AVVISO DI CONFERENZA

GIOVEDI’ 23 APRILE 2015, ore 16:30, AULA A1 (III piano)

 

Dott. ALESSANDRO FORTUNELLI

CNR-ICCOM, Pisa, Italy and Caltech, Mat & Proc Simulat Ctr, Pasadena, CA, USA

 

Properties of Nanostructured Metals via Predictive Quantum Approaches

 


Alessandro Fortunelli 1,2


1 CNR-ICCOM, via Giuseppe Moruzzi 1, 56124, Pisa, Italy
2 Caltech, Mat & Proc Simulat Ctr, MC 139-74, Pasadena, CA 91125 USA
E-mail: alessandro.fortunelli@cnr.it, afloer@caltech.edu


In this talk I will present some results of our work aimed at building a predictive computational materials science, with the underlying theme of investigating materials with nanoscale structural features and searching for associated novel and possibly exploitable phenomena and properties. In particular, I will focus on recent advances in the theoretical description of the properties of metal nanostructures, in which the simulation of kinetics and dynamic phenomena, such structural dynamics and catalysis, are explored via quantum mechanical approaches.
Starting from the smallest systems, sub-nanometer supported metal clusters (containing few up to 10-20 metal atoms) represent a new class of materials which can exhibit superior catalytic properties in efficiency and selectivity with respect to traditional catalytic systems in addition to optimizing atom-economy efficiency1. A Reactive Glocal Optimization (RGO) approach will be discussed as a computational technique able to explore the reactive phase space of these systems in the presence of reactant molecules (heterogeneous ultrananocatalysis)2. The RGO approach will be framed within the general theme of the long-term structural dynamics of kinetics-driven off-lattice activated processes: generalizations to larger systems will be introduced, with application to the kinetics of compositional structure or elemental diffusion in nanoalloys and the issue of size-dependent spontaneous alloying (enhanced diffusion)3. Recent results on the oxygen reduction reaction (ORR) catalyzed by platinum also in “exotic” nanostructures such as nanoporous ones obtained via de-alloying of Ni-Pt particles will also be illustrated4. Nanoporous metals, i.e., metallic structures whose framework exhibits continuously connected cavities (pores) of nanoscale size, have attracted an explosive interest in the last 15 years due to their unique properties leading to applications in catalysis, sensors, and opto-electronic devices. Despite an intense experimental effort, lack of fundamental knowledge still remains on these systems concerning their geometric features and the relationships between these features and the corresponding properties. Here we achieve knowledge and understanding on the atomistic structure of nanoporous metallic systems via first-principles-based simulations, focusing on the prototypical case of nanoporous Pt obtained by dealloying of Ni-Pt nanoparticles and its superior catalytic activity in the ORR which is the rate determining step in low-temperature hydrogen fuel cells for sustainable and energy-efficient electrical power.
If time allows, electron dynamics will be considered. The prediction of the optical response of metal nanoclusters and nanoalloys (both bare and coated by a shell of ligands), nanocages and nanowires will be demonstrated using time-dependent density-functional-theory (TDDFT), and the dependence of plasmonic peaks upon stoichiometry and chemical ordering will be analyzed5, together with its dependence upon inter-particle distance to explore coupled plasmonics effects and „hot-spot‟ enhancement of response fields6. The modulation of interfacial electronic states of a metal surface is coated with a dielectric will finally be discussed7.

 

  1. A. A. Herzing et al., Science 321, 1331 (2008); Y. Lei, et al., Science 328, 224 (2010).
  2. F. R. Negreiros, et al., Nanoscale 4, 1208 (2012); ACS Cat. 2, 1860 (2012); Compt. Rendue Chim. “Concepts in theoretical heterogeneous ultrananocatalysis” 17, 625-633 (2014).
  3. M. Asgari et al., “Striking dependence of diffusion kinetics in Ag–Cu nanoalloys upon composition and quantum effects” 141, 041108 (2014).
  4. A. Fortunelli et al., 5Angew. Chem. Int. Ed. 53, 6669 (2014); Nanoscale 7, 4514 (2015).
  5. N. Durante et al., J. Phys. Chem. C 115, 6277 (2011); G. Barcaro et al., J. Phys. Chem. C 115, 24085 (2011).
  6. L. Sementa et al., ACS Phot. 1, 315–322 (2014).
  7. L. Sementa et al., Phys. Rev. B 88, 125413 (2013).
Ultimo aggiornamento: 27-04-2015 - 16:57
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