Atomistic simulations of stress/strain maps of alloyed nanoparticles

In the context of energy, environment and sustainable developments, the prospective replacements for internal combustion engines are proton exchange Polymer Electrolyte Membrane Fuel Cells (PEMFC) where platinum electrodes convert Oxygen and Hydrogen into water via an electrocatalytic reaction. Because of high cost and scarcity of Pt, it is convenient to use Pt-based alloys which can display even better efficiencies than pure Pt catalysts [1]. We propose here a theoretical study of the atomic structure and chemical ordering of Pt-based nanoparticles of alloys (Pt-M, M=Co, Pd, Ag) and in particular the stress/strain map of the nanoparticles since it is well known that the strain has a high impact on the reactivity [2]. We propose a systematic study of the stress/strain map at the atomic scale of nanoparticles of alloys where both the finite size of nanoparticle, the misfit between the two elements and the consequence of phase boundaries or grain boundaries in the core deform the atomic structure at the surface of the nanoparticles where takes place the catalytic reaction. We performed ab initio calculations on model and small system , and extensive Monte Carlo simulations on larger ones using semi-empirical many-body potentials to optimize their chemical configurations to get realistic systems to be compared to the experiments [3]. The stress and strain analysis is then obtained by quenched molecular dynamics.

[1] V. R. Stamenkovic, B. Fowler, B.S. Mun, G. Wang, P.N. Ross, C.A. Lucas, N.M. Markovic, Science 315, 493 (2007)

[2] T.N. Pingel, M. Jorgensen, A.BL Yankovich, H. Grönbeck, E. Olsson, Nat. Com. 9, 2722 (2018)

[3] J. Pirart, A. Front, D. Rapetti, C. Andreazza, P. Andreazza, C. Mottet, R. Ferrando, Nature Communication, accepted (2019)