Understanding the structure and reactivity of NiCu nanoparticles: an atomistic modeling

Transcription

1 Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is the Owner Societies 2017 Understanding the structure and reactivity of NiCu nanoparticles: an atomistic modeling P. Quaino1*, G. Belletti1, S.A. Shermukhamedov2, D. Glukhov2, E.Santos3,4, W. Schmickler3, R. Nazmutdinov2* 1 Instituto de Quıı mica Aplicada del Litoral, IQAL (UNL-CONICET), PRELINE (FIQ-UNL), Santa Fe, Argentina 2 Kazan National Research Technological University, Kazan, Republic of Tatarstan, Russian Federation 3 Institute of Theoretical Chemistry, Ulm University, D Ulm, Germany 4 Faculdad de Matematica, Astronomıı a y Física, Instituto de Física Enrique Gaviola (IFEG-CONICET), Universidad Nacional de Co rdoba, 5000 Co rdoba, Argentina Corresponding authors S.1. Futher structural information 2.5 %

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12 Figure 1S: Nanoparticles of 8554 atoms (d = 6.6 nm). For each investigated compositions: geometry, cross section, radial and angular distributions are showed. 10%

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17 Figure 2S: Nanoparticles of 2057 atoms (d = 2.2 nm). For each investigated compositions: geometry, cross section, radial and angular distributions are showed. a Figure 3S: b c Optimized structure of cubic NiCu nanoparticles (Natoms = 319) with three different faces, (100), (110) and (331), obtained from the lattice MC simulations; x(cu) = 0.05 a, x(cu) = 0.5 a, x(cu) = 0.25 c. The nickel atoms are marked with green.

18 T= 900 K T = 20 K cross-sectional view cross-sectional view Figure 4S: Optimized structure of two NiCu nanoparticles of different size (Natoms = 1111, x(cu) = 0.75 obtained from MD simulations at two different temperatures. The nickel atoms are marked with green. S.2. Futher computational information Periodic Calculations: all calculations were performed using the JACAPO code [1]. This utilizes an iterative scheme to solve the Kohn-Sham equations of density functional theory self-consistently. A plane-wave basis set is used to expand the electronic wave functions, and the inner electrons were represented by ultrasoft pseudopotentials [2], which allow the use of a low energy cut-off for the plane wave basis set. An energy cut-off 450 ev, dictated by the pseudopotential of each metal, was used. The electron-electron exchange and correlation interactions are treated with the generalized gradient approximation in the version of Perdew et al [3]. The Brillouin-zone integration was performed using a 8 x 8 x 1 k-point Monkhorst-Pack grid [4], corresponding to the 1x1 surface unit cell. Spin polarization was not considered. Dipole correction was used to avoid slab-slab interactions [5]. In all the calculations a vacuum corresponding to 12 Å was used. The structures shown in Table 1 of the manuscript were designed to mimic different combinations and configurations of both metals found in the bimetallic NPs. Cluster Calculations: to evaluate the heat of the reaction (s.1) ( E) and its activation barrier ( Ea) for two different model clusters of Cu and Ni, non-periodic calculations have been performed. The metal surface was

19 modeled by small four-atomic clusters. DFT calculations were carried out by using the B3LyP hybrid functional as implemented in the Gaussian program suit [6]. The electrons of Cu, Ni, O and H atoms were described by the 6-31+g(d, p) basis set. The spin-polarized formalism was employed. The initial and final states of the process (s.1) are shown in Fig. 5S. H(ads) + OH(ads) H2O (s.1) Figure 5S: The initial (left) and final (right) states of the model process (1) at the model metal clusters. Table 1S: The heat of model reaction (s.1) ( ΔE ) and its activation barrier ( ΔEa ) calculated for two different model clusters of Cu and Ni. Metal ΔE/eV ΔEa/eV Cu Ni References 1-Hammer, B.; Hansen, L. B.; Nørskov, J. K., Phys. Rev. B 59: , Vanderbilt, D., Phys. Rev. B 41: , Perdew, J. P.; Burke, K.; Ernzerhof, M., Phys. Rev. Lett. 77: , Monkhorst, H. J.; Pack, J. D., Phys. Rev. B 13: , Bengtsson, L., Phys. Rev. B 59: , Gaussian 03, Revision B.04, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria et al.