@misc{MerteBraudBussetal., author = {Merte, Lindsay R. and Braud, Nicolas and Buß, Lars and Bisbo, Malthe Kj{\ae}r and Wallander, Harald J. and Krisponeit, Jon-Olaf and Flege, Jan Ingo and Hammer, Bj{\o}rk and Falta, Jens and Lundgren, Edvin}, title = {Oxygen Storage by Tin Oxide Monolayers on Pt3Sn(111)}, series = {The Journal of Physical Chemistry. C}, volume = {127}, journal = {The Journal of Physical Chemistry. C}, number = {6}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.2c09041}, pages = {2988 -- 2994}, abstract = {The high performance of platinum-tin catalysts for oxidation reactions has been linked to the formation of tin oxides at the metal surface, but little is known about the structure of these oxides or the chemical behavior that determines their catalytic properties. We show here how surface oxides on Pt3Sn(111) incorporate oxygen at the metal interface, which may be subsequently removed by reaction with CO. The storage mechanism, where oxygen uptake occurs without loss of interfacial Pt-Sn bonds, is enabled by the peculiar asymmetrical coordination state of Sn2+. O atoms are bound at pocket sites in the 2D oxide sheet between these outward-buckled Sn atoms and metallic Sn in the alloy surface below.}, language = {en} } @misc{WallanderGajdekAlbertinetal., author = {Wallander, Harald J. and Gajdek, Dorotea and Albertin, Stefano and Harlow, Gary and Braud, Nicolas and Buß, Lars and Krisponeit, Jon-Olaf and Flege, Jan Ingo and Falta, Jens and Lundgren, Edvin and Merte, Lindsay R.}, title = {Dynamic Behavior of Tin at Platinum Surfaces during Catalytic CO Oxidation}, series = {ACS Catalysis}, volume = {13}, journal = {ACS Catalysis}, number = {24}, issn = {2155-5435}, doi = {10.1021/acscatal.3c04657}, pages = {16158 -- 16167}, abstract = {Platinum-tin surfaces are active for CO oxidation, but their activity and the effects of tin oxide phases that form under reaction conditions are poorly understood. We have studied surface alloys of tin prepared on platinum single crystals during catalytic CO oxidation using near-ambient-pressure X-ray photoemission spectroscopy. On the flat terraces of Sn/Pt(111), a wetting layer of Sn(II) surface oxide forms, while on the stepped Sn/Pt(223) surface, 3D clusters of Sn(IV) oxide are formed. Oxidation of tin by O2 competes with the reduction of the oxides by CO under reaction conditions. Oxides that do not completely cover the surface can be reduced to metallic tin, while a fully covering layer of Sn(II) oxide cannot, showing the importance of oxide edge sites for the reduction process. The samples where 2D oxide layers are formed show a higher CO oxidation activity than for pure platinum at low temperatures, while the Sn(IV) oxide clusters on the stepped surfaces do not affect the measured CO oxidation rate. We therefore identify 2D Sn(II) oxide as an active phase for CO oxidation. While oxide island edges appear to make only minor contributions to conversion under these conditions, reactions at these sites play a major role in determining the phases present and their transformations.}, language = {en} } @misc{BraudBussLundgrenetal., author = {Braud, Nicolas and Buß, Lars and Lundgren, Edvin and Merte, Lindsay R. and Wallander, Harald J. and Krisponeit, Jon-Olaf and Locatelli, Andrea and Mentes, Tevfik Onur and Jugovac, Matteo and Flege, Jan Ingo and Falta, Jens}, title = {Cleaning and tailoring the Pt3Sn(111) surface for surface experiments}, series = {Surface Science}, volume = {732}, journal = {Surface Science}, issn = {0039-6028}, doi = {10.1016/j.susc.2023.122281}, abstract = {The cleaning process of the bimetallic Pt3Sn(111) surface has been studied by means of low-energy electron microscopy (LEEM), microspot low-energy electron diffraction (-LEED), and X-ray photoemission electron microscopy (XPEEM). Different cleaning procedures, performed under ultra-high vacuum conditions (UHV), including sputtering with argon ions and repeated cycles of annealing up to 1500 K were investigated. In this work, we show that a clean Pt3Sn(111) surface of high structural quality with a sharp and brilliant (2 × 2) bulk reconstruction in LEED as well as a perfectly smooth surface with terraces of micron size can be achieved by sputtering, annealing at very high temperatures, followed by a subsequent slow (0.09 K/s) and careful cooling procedure. Additionally, we show the possibility of tailoring the Sn concentration in the topmost layers of Pt3Sn(111) as a function of annealing temperature and subsequent cooling rate. Structural changes of the surface are induced by Sn segregation combined with a surface order-disorder transition at 1340 K. Moreover, two new surface reconstructions depending on the cooling rate are reported.}, language = {en} }