Evaluation of the Electrochemical Stability of Model Cu-Pt(111) Near-Surface Alloy Catalysts

• Published in: Electrochimica acta 2015-10, Vol.179, p.469-474
• Main Authors: Tymoczko, Jakub, Calle-Vallejo, Federico, Čolić, Viktor, Schuhmann, Wolfgang, Bandarenka, Aliaksandr S.
• Format: Article
• Language: English
• Subjects: Electrocatalysis; Electrochemical interface; Stability, Cu-Pt near-surface alloys
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2015.02.110

[Display omitted] •Theoretical and experimental evaluation of model electrocatalyst stability.•Cu atomic layer is stabilized in the subsurface layer at Pt(111).•After 5000 cycles ca 50% of Cu still remains in the subsurface region. Better understanding of the factors responsible for the long-term stability of electrocatalysts is of increasing importance for the development of new generations of efficient electrode materials relevant for sustainable energy provision. Therefore, experiments with model, often single-crystal catalytic surfaces are of significance for fundamental electrochemistry and technological applications. Among model electrocatalysts, near-surface alloys (NSAs) of Pt with Cu, Ni and other metals formed via electrochemical deposition and thermal annealing have shown remarkable properties, demonstrating high activity towards a number of important reactions, including the oxygen reduction reaction (ORR) and CO oxidation. However, relatively little is known about the electrochemical stability and mechanisms of degradation of model NSAs. In this work, we employ a simple electrochemical approach, supported by density functional theory calculations, to evaluate the stability of Cu-Pt(111) NSAs in 0.1M HClO4. Our results show that ∼30% of the Cu atoms initially incorporated into the second atomic layer of Pt are lost within the first 2000 cycles performed between 0.05V and 1.0V (RHE). After 5000 cycles, ca. half of the Cu atoms initially placed in the second atomic layer still remained in the subsurface region. The dissolution of Cu has a substantial impact on the measured shift in the average OH-binding energy for the catalyst surface and, consequently, on the ORR activity. Interestingly, after dissolution of Cu from NSAs, voltammetric features, which are characteristic to the Pt(111) facets, are partially restored suggesting the formation of NSA and Pt(111) domains in the resulting surface.