The bimetallic core–shell nanoparticles (CSNPs) exhibit superior stability, selectivity, and catalytic activity as well as display new functions owing to a lattice strain induced by the unique core-shell structures and synergistic effects of different metal components. These properties of bimetallic CSNPs can be tuned and expanded by varying the composition and atomic arrangement as well as their sizes, morphology, thickness, and sequence of both core and shell. In this study, the geometrical structure, thermodynamic stability, and electronic properties of 13- and 55-atom Cu, Pd nanoparticles (NPs), and Cu–Pd CSNPs were systematically investigated using density functional theory calculations. The results showed that Pd atoms prefer to segregate to the surface shell, while Cu atoms were inclined to aggregate in the core region for bimetallic Cu–Pd CSNPs; therefore, Cu@Pd CSNPs with a Pd surface-shell were thermodynamically more favourable than both the monometallic Cu/Pd NPs and the Pd@Cu CSNPs with a Cu surface-shell. The charge transfer increased from the Cu-core to the Pd-shell for the Cu@Pd CSNPs, while it decreased from the Pd-core to the Cu-shell for the Pd@Cu CSNPs. Opposite charge transfer in these CSNPs led to the Pd surface-shell that displays a negative charge, while the Cu surface-shell exhibits a positive charge.

Xueyan Hu, Yangyang Zhang, Xiaolei Zhao, Yulong Zhang. Theoretical study of Cu–Pd core–shell nanoparticles: structure, stability and electronic. Academic Journal of Materials & Chemistry (2024) Vol. 5, Issue 2: 29-36. https://doi.org/10.25236/AJMC.2024.050206.

[1] Wei S, Wang Q, Zhu J, et al. Multifunctional composite core–shell nanoparticles[J]. Nanoscale, 2011, 3(11): 4474-4502.

[2] Sun Q, Zhang X Q, Wang Y, et al. Recent progress on core-shell nanocatalysts[J]. Chinese Journal of Catalysis, 2015, 36(5): 683-691.

[3] Gawande M B, Goswami A, Asefa T, et al. Core–shell nanoparticles: synthesis and applications in catalysis and electrocatalysis[J]. Chemical Society Reviews, 2015, 44(21): 7540-7590.

[4] Henning A M, Watt J, Miedziak P J, et al. Gold–Palladium Core–Shell Nanocrystals with Size and Shape Control Optimized for Catalytic Performance[J]. Angewandte Chemie International Edition, 2013, 52(5): 1477-1480.

[5] Vysakh A B, Babu C L, Vinod C P. Demonstration of Synergistic Catalysis in Au@Ni Bimetallic Core–Shell Nanostructures[J]. The Journal of Physical Chemistry C, 2015, 119(15): 8138-8146.

[6] Guisbiers G, Khanal S, Ruiz-Zepeda F, et al. Cu–Ni nano-alloy: mixed, core–shell or Janus nano-particle [J]. Nanoscale, 2014, 6(24): 14630-14635.

[7] Feng X, Shi D, Jia J, et al. Structural, mixing, electronic and magnetic properties of small Cu-Pd nanoalloy clusters[J]. Materials Today Communications, 2022, 31: 103222.

[8] Wu X, Zhang Y. Structural differences of Cu-Pd clusters with three potential parameters[J]. Chemical Physics Letters, 2024, 842: 141200.

[9] Choi K I, Vannice M A. CO oxidation over Pd and Cu catalysts V. Al2O3-supported bimetallic Pd-Cu particles[J]. Journal of Catalysis, 1991, 131(1): 36-50.

[10] Mierczynski P, Vasilev K, Mierczynska A, et al. Highly selective Pd–Cu/ZnAl2O4 catalyst for hydrogen production[J]. Applied Catalysis A: General, 2014, 479: 26-34.

[11] Greeley J, Nørskov J K, Kibler L A, et al. Hydrogen Evolution Over Bimetallic Systems: Understanding the Trends[J]. ChemPhysChem, 2006, 7(5): 1032-1035.

[12] Feilong Xing, Jaewan Jeon, Takashi Toyao, Ken-ichi Shimizu, and Shinya Furukawa. A Cu–Pd single-atom alloy catalyst for highly efficient NO reduction [J]. Chemical Science, 2019, 10(36): 8292-8298.

[13] Phillips J, Auroux A, Bergeret G, et al. Phase behavior of palladium-silver particles supported on silica [J]. The Journal of Physical Chemistry, 1993, 97(14): 3565-3570.

[14] Alvarez-Garcia A, Flórez E, Moreno A, et al. CO2 activation on small Cu-Ni and Cu-Pd bimetallic clusters [J]. Molecular Catalysis, 2020, 484: 110733.

[15] Gómez Herranz A, Germán E, Alonso J A, et al. Interaction of hydrogen with palladium–copper nanoalloys[J]. Theoretical Chemistry Accounts, 2021, 140(4): 35.

[16] Luna-Valenzuela A, Cabellos J L, Alonso J A, et al. Effects of van der Waals interactions on the structure and stability of Cu8-xPdx (x = 0, 4, 8) cluster isomers[J]. Materials Today Communications, 2021, 26: 102024.

[17] Chen D, Wang Y, Liu D, et al. Surface composition dominates the electrocatalytic reduction of CO 2 on ultrafine CuPd nanoalloys[J]. Carbon Energy, 2020, 2(3): 443-451.

[18] Geisler A H, Newkirk J B. Ordering Reaction of the Cu4Pd Alloy[J]. JOM, 1954, 6(9): 1076-1082.

[19] Paniago R, de Siervo A, Soares E A, et al. Pd growth on Cu (111): stress relaxation through surface alloying [J]. Surface Science, 2004, 560(1): 27-34.

[20] Canzian A, Mosca H O, Bozzolo G. Surface alloying of Pd on Cu (111) [J]. Surface Science, 2004, 551(1): 9-22.

[21] Zhu L, Liang K S, Zhang B, et al. Bimetallic Pd–Cu Catalysts: X-Ray Diffraction and Theoretical Modeling Studies[J]. Journal of Catalysis, 1997, 167(2): 412-416.

[22] Montejano-Carrizales J M, I.Iguez M P, Alonso J A. Embedded-atom method applied to bimetallic clusters: The Cu-Ni and Cu-Pd systems[J]. Physical Review B Condensed Matter, 1994, 49(23): 16649.

[23] van Langeveld A D, Hendrickx H A C M, Nieuwenhuys B E. The surface composition of Pd-Cu alloys: A comparative investigation of photoelectric work function measurements, Auger electron spectroscopy and calculations based on a broken bond approximation[J]. Thin Solid Films, 1983, 109(2): 179-192.

[24] Miller J B, Matranga C, Gellman A J. Surface segregation in a polycrystalline Pd70Cu30 alloy hydrogen purification membrane[J]. Surface Science, 2008, 602(1): 375-382.

[25] Jl. R, Miegge P, Jc. B. Theory of segregation using the equivalent-medium approximation and bond-strength modifications at surfaces: Application to fcc Pd-X alloys. [J]. Physical Review.B.Condensed Matter, 1996(8): 53.

[26] Fernández-García M, Anderson J A, Haller G L. Alloy Formation and Stability in Pd−Cu Bimetallic Catalysts[J]. The Journal of Physical Chemistry, 1996, 100(40): 16247-16254.

[27] Gai P L, Smith B C. Dynamic electron microscopy of copper-palladium intermetallic compound catalysts [J]. Ultramicroscopy, 1990, 34(1): 17-26.

[28] Xuan J, Hong W, Chuannan G. Preparation of Core-Shell Cu@Pt-Pd Electrode for Fuel Cells by High Temperature Reduction of Ethylene Glycol[J]. Yunnan Chemical Technology, 2019.

[29] Yang C L, Zhang X H, Lan G, et al. Pd-based nanoporous metals for enzyme-free electrochemical glucose sensors [J]. China ChemExpress: English version, 2014(4): 496-500.

[30] Calabro R L, Burpo F J, Bartolucci S F, et al. Seed-Mediated Growth of Oxidation-Resistant Copper Nanoparticles[J]. The Journal of Physical Chemistry C, 2023, 127(31): 15307-15315.

[31] Tang Z, Han G H, Jung E, et al. Synthesis of Cu-Pd nanoplates and their catalytic performance for H2O2 generation reaction[J]. Molecular Catalysis, 2018, 452: 117-122.

[32] Allemand M, Martin Manuel H, Reyter D, et al. Synthesis of Cu–Pd alloy thin films by co-electrodeposition[J]. Electrochimica Acta, 2011, 56(21): 7397-7403.

[33] Kresse G, Furthmüller J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set[J]. Computational Materials Science, 1996, 6(1): 15-50.

[34] Kresse G, Joubert D. From ultrasoft pseudopotentials to the projector augmented-wave method[J]. Physical Review B, 1999, 59(3): 1758-1775.

[35] Blöchl P E. Projector augmented-wave method[J]. Physical Review B, 1994, 50(24): 17953-17979.

[36] Perdew J P, Burke K, Ernzerhof M. Generalized Gradient Approximation Made Simple[J]. Physical Review Letters, 1996, 77(18): 3865-3868.

[37] Sanville E, Kenny S D, Smith R, et al. Improved grid‐based algorithm for Bader charge allocation [J]. Journal of Computational Chemistry, 2007, 28(5): 899-908.

[38] Henkelman G, Arnaldsson A, Jónsson H. A fast and robust algorithm for Bader decomposition of charge density [J]. Computational Materials Science, 2006, 36(3): 354-360.

[39] Yang Z, Wang Q, Shan X, et al. DFT study of Fe-Ni core-shell nanoparticles: Stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth[J]. The Journal of Chemical Physics, 2015, 142(7): 074306.

[40] Xiang Y, Sun D Y, Gong X G. Generalized Simulated Annealing Studies on Structures and Properties of Nin (n = 2−55) Clusters[J]. The Journal of Physical Chemistry A, 2000, 104(12): 2746-2751.

[41] Singh R, Kroll P. Structural, electronic, and magnetic properties of 13-, 55-, and 147-atom clusters of Fe, Co, and Ni: A spin-polarized density functional study[J]. Physical Review B, 2008, 78(24): 245404.

[42] Knickelbein M B. Electric dipole polarizabilities of Ni12–58[J]. The Journal of Chemical Physics, 2001, 115(13): 5957-5964.

[43] Böyükata M, Belchior J C. Structural and energetic analysis of copper clusters: MD study of Cu n (n = 2-45) [J]. Journal of the Brazilian Chemical Society, 2008, 19(5): 884-893.

[44] Sahoo S, Rollmann G, Entel P. Segregation and ordering in binary transition metal clusters[J]. Phase Transitions, 2006, 79(9-10): 693-700.

[45] Ferrando R, Jellinek J, Johnston R L. Nanoalloys: From Theory to Applications of Alloy Clusters and Nanoparticles [J]. Chemical Reviews, 2008, 108(3): 845-910.

[46] Allred A L. Electronegativity values from thermochemical data[J]. Journal of Inorganic and Nuclear Chemistry, 1961, 17(3): 215-221.