Formation of a 2D Meta-stable Oxide by Differential Oxidation of AgCu Alloys

Schweinar K, Beeg S, Hartwig C, Rajamathi CR, Kasian O, Piccinin S, Prieto MJ, Tanase LC, Gottlob DM, Schmidt T, Raabe D, Schlogl R, Gault B, Jones TE, Greiner MT (2020)

Publication Type: Journal article

Publication year: 2020

Journal

ACS Applied Materials and Interfaces American Chemical Society

Book Volume: 12

Pages Range: 23595-23605

Journal Issue: 20

DOI: 10.1021/acsami.0c03963

Abstract

Metal alloy catalysts can develop complex surface structures when exposed to reactive atmospheres. The structures of the resulting surfaces have intricate relationships with a myriad of factors, such as the affinity of the individual alloying elements to the components of the gas atmosphere and the bond strengths of the multitude of low-energy surface compounds that can be formed. Identifying the atomic structure of such surfaces is a prerequisite for establishing structure-property relationships, as well as for modeling such catalysts in ab initio calculations. Here, we show that an alloy, consisting of an oxophilic metal (Cu) diluted into a noble metal (Ag), forms a meta-stable two-dimensional oxide monolayer, when the alloy is subjected to oxidative reaction conditions. The presence of this oxide is correlated with selectivity in the corresponding test reaction of ethylene epoxidation. In the present study, using a combination of in situ, ex situ, and theoretical methods (NAP-XPS, XPEEM, LEED, and DFT), we determine the structure to be a two-dimensional analogue of Cu2O, resembling a single lattice plane of Cu2O. The overlayer holds a pseudo-epitaxial relationship with the underlying noble metal. Spectroscopic evidence shows that the oxide's electronic structure is qualitatively distinct from its three-dimensional counterpart, and because of weak electronic coupling with the underlying noble metal, it exhibits metallic properties. These findings provide precise details of this peculiar structure and valuable insights into how alloying can enhance catalytic properties.

Involved external institutions

Fritz-Haber-Institut der Max-Planck-Gesellschaft (FHI) DE Germany (DE) Max-Planck-Institut für Eisenforschung GmbH (MPIE) / Max Planck Institute for Iron Research DE Germany (DE) Max-Planck-Institut für Chemische Energiekonversion (MPI CEC) / Max-Planck-Institute for Chemical Energy Conversion DE Germany (DE) Consiglio Nazionale delle Ricerche (CNR) / National Research Council of Italy IT Italy (IT)

How to cite

APA:

Schweinar, K., Beeg, S., Hartwig, C., Rajamathi, C.R., Kasian, O., Piccinin, S.,... Greiner, M.T. (2020). Formation of a 2D Meta-stable Oxide by Differential Oxidation of AgCu Alloys. ACS Applied Materials and Interfaces, 12(20), 23595-23605. https://doi.org/10.1021/acsami.0c03963

MLA:

Schweinar, Kevin, et al. "Formation of a 2D Meta-stable Oxide by Differential Oxidation of AgCu Alloys." ACS Applied Materials and Interfaces 12.20 (2020): 23595-23605.

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