{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,11]],"date-time":"2025-11-11T13:45:06Z","timestamp":1762868706081,"version":"build-2065373602"},"reference-count":48,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2021,12,4]],"date-time":"2021-12-04T00:00:00Z","timestamp":1638576000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012190","name":"Ministry of Science and Higher Education of the Russian Federation","doi-asserted-by":"publisher","award":["Budget project  for the Synchrotron Radiation Facility SKIF, Boreskov Institute of Catalysis"],"award-info":[{"award-number":["Budget project  for the Synchrotron Radiation Facility SKIF, Boreskov Institute of Catalysis"]}],"id":[{"id":"10.13039\/501100012190","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>In this study, the dependence of the catalytic activity of highly oriented pyrolytic graphite (HOPG)-supported bimetallic Pd-Au catalysts towards the CO oxidation based on the Pd\/Au atomic ratio was investigated. The activities of two model catalysts differing from each other in the initial Pd\/Au atomic ratios appeared as distinctly different in terms of their ignition temperatures. More specifically, the PdAu-2 sample with a lower Pd\/Au surface ratio (~0.75) was already active at temperatures less than 150 \u00b0C, while the PdAu-1 sample with a higher Pd\/Au surface ratio (~1.0) became active only at temperatures above 200 \u00b0C. NAP XPS revealed that the exposure of the catalysts to a reaction mixture at RT induces the palladium surface segregation accompanied by an enrichment of the near-surface regions of the two-component Pd-Au alloy nanoparticles with Pd due to adsorption of CO on palladium atoms. The segregation extent depends on the initial Pd\/Au surface ratio. The difference in activity between these two catalysts is determined by the presence or higher concentration of specific active Pd sites on the surface of bimetallic particles, i.e., by the ensemble effect. Upon cooling the sample down to room temperature, the reverse redistribution of the atomic composition within near-surface regions occurs, which switches the catalyst back into inactive state. This observation strongly suggests that the optimum active sites emerge under reaction conditions exclusively, involving both high temperature and a reactive atmosphere.<\/jats:p>","DOI":"10.3390\/nano11123292","type":"journal-article","created":{"date-parts":[[2021,12,6]],"date-time":"2021-12-06T03:10:38Z","timestamp":1638760238000},"page":"3292","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Near-Ambient Pressure XPS and MS Study of CO Oxidation over Model Pd-Au\/HOPG Catalysts: The Effect of the Metal Ratio"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0199-8111","authenticated-orcid":false,"given":"Andrey V.","family":"Bukhtiyarov","sequence":"first","affiliation":[{"name":"Synchrotron Radiation Facility SKIF, Boreskov Institute of Catalysis SB RAS, 630559 Kol\u2019tsovo, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Igor P.","family":"Prosvirin","sequence":"additional","affiliation":[{"name":"Department of Physicochemical Techniques, Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6897-7692","authenticated-orcid":false,"given":"Maxim A.","family":"Panafidin","sequence":"additional","affiliation":[{"name":"Synchrotron Radiation Facility SKIF, Boreskov Institute of Catalysis SB RAS, 630559 Kol\u2019tsovo, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1933-5770","authenticated-orcid":false,"given":"Alexey Yu.","family":"Fedorov","sequence":"additional","affiliation":[{"name":"Department of Physicochemical Techniques, Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia"},{"name":"Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexander Yu.","family":"Klyushin","sequence":"additional","affiliation":[{"name":"Inorganic Chemistry Department, Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany"},{"name":"BESSY II, Helmholtz Center for Materials and Energy, 12489 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Axel","family":"Knop-Gericke","sequence":"additional","affiliation":[{"name":"Inorganic Chemistry Department, Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany"},{"name":"Department of Heterogeneous Reactions, Max Planck Institute for Chemical Energy Conversion, 45470 M\u00fclheim an der Ruhr, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2266-8944","authenticated-orcid":false,"given":"Yan V.","family":"Zubavichus","sequence":"additional","affiliation":[{"name":"Synchrotron Radiation Facility SKIF, Boreskov Institute of Catalysis SB RAS, 630559 Kol\u2019tsovo, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Valery I.","family":"Bukhtiyarov","sequence":"additional","affiliation":[{"name":"Department of Physicochemical Techniques, Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1021\/acscatal.6b02054","article-title":"Tuning Catalytic Performance through a Single or Sequential Post-Synthesis Reaction(s) in a Gas Phase","volume":"7","author":"Shan","year":"2017","journal-title":"ACS Catal."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1070\/RC2001v070n02ABEH000637","article-title":"Metallic Nanosystems in Catalysis","volume":"70","author":"Bukhtiyarov","year":"2001","journal-title":"Russ. 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