TY - JOUR

T1 - The effect of CO treatment on the surface structure of bimetallic Pd-Au/HOPG and Pd-In/HOPG nanoparticles: A comparative study

AU - Fedorov, A. Yu

AU - Bukhtiyarov, A. V.

AU - Panafidin, M. A.

AU - Prosvirin, I. P.

AU - Chetyrin, I. A.

AU - Smirnova, N. S.

AU - Markov, P. V.

AU - Zubavichus, Y. V.

AU - Stakheev, A. Yu

AU - Bukhtiyarov, V. I.

N1 - Funding Information: This work was supported by the Russian Science Foundation (grant no. 19-13-00285 ). Publisher Copyright: © 2021 Elsevier B.V.

PY - 2022/2

Y1 - 2022/2

N2 - Bimetallic nanoparticles have been attracting more and more attention as catalysts in recent years since they often provide improved catalytic performance when compared to their monometallic analogues. Trying to design the optimum configuration of active sites in such catalytic systems, researchers resort to different strategies, one of which consists of a specific pretreatment of pre-synthesized nanoparticles in a particular gaseous environment prior to the catalytic reaction, resulting in adsorption-induced segregation. However, such a strategy does not always lead to any significant changes in the surface structure, so the identification of all factors responsible for the segregation process is of high fundamental and applied interest for the targeted design of bimetallic catalytically active nanoparticles. Here we show that for two types of bimetallic nanosystems, a stoichiometric intermetallic compound of Pd and In, and a substitutional solid solution of Pd and Au, the exposure to a CO atmosphere leads to completely different results, i.e., a noticeable surface segregation of Pd atoms being observed exclusively for the latter system. Driven by adsorption of CO molecules, the process of segregation is enhanced in the studied Pd-Au/HOPG catalyst (initial Pd/Au ratio of 1.48) when the temperature of the CO treatment is increased to 150 °C. In contrast, the Pd-In/HOPG nanoparticles (initial Pd/In ratio of 1.35) show no considerable change in the apparent surface atomic composition under a CO atmosphere, irrespective of temperature. Our results, alongside previous findings, demonstrate that CO adsorption-induced segregation as a tool for target-oriented modification of active sites in bimetallic nanoparticles for catalytic applications is appropriate only for substitutional solid solutions having a reasonable number of contacts between atoms of one type prone to segregation.

AB - Bimetallic nanoparticles have been attracting more and more attention as catalysts in recent years since they often provide improved catalytic performance when compared to their monometallic analogues. Trying to design the optimum configuration of active sites in such catalytic systems, researchers resort to different strategies, one of which consists of a specific pretreatment of pre-synthesized nanoparticles in a particular gaseous environment prior to the catalytic reaction, resulting in adsorption-induced segregation. However, such a strategy does not always lead to any significant changes in the surface structure, so the identification of all factors responsible for the segregation process is of high fundamental and applied interest for the targeted design of bimetallic catalytically active nanoparticles. Here we show that for two types of bimetallic nanosystems, a stoichiometric intermetallic compound of Pd and In, and a substitutional solid solution of Pd and Au, the exposure to a CO atmosphere leads to completely different results, i.e., a noticeable surface segregation of Pd atoms being observed exclusively for the latter system. Driven by adsorption of CO molecules, the process of segregation is enhanced in the studied Pd-Au/HOPG catalyst (initial Pd/Au ratio of 1.48) when the temperature of the CO treatment is increased to 150 °C. In contrast, the Pd-In/HOPG nanoparticles (initial Pd/In ratio of 1.35) show no considerable change in the apparent surface atomic composition under a CO atmosphere, irrespective of temperature. Our results, alongside previous findings, demonstrate that CO adsorption-induced segregation as a tool for target-oriented modification of active sites in bimetallic nanoparticles for catalytic applications is appropriate only for substitutional solid solutions having a reasonable number of contacts between atoms of one type prone to segregation.

KW - Adsorption induced segregation

KW - Alloy design

KW - Heterogeneous supported catalysts

KW - Intermetallic nanoparticles

KW - Scanning tunneling microscopy

KW - X-ray photoelectron spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=85121604687&partnerID=8YFLogxK

U2 - 10.1016/j.nanoso.2021.100830

DO - 10.1016/j.nanoso.2021.100830

M3 - Article

AN - SCOPUS:85121604687

VL - 29

JO - Nano-Structures and Nano-Objects

JF - Nano-Structures and Nano-Objects

SN - 2352-507X

M1 - 100830

ER -