title: Cobalt monolayer islands on Ag(111) for ORR catalysis.
abstract: The design of a catalyst for one of the most important electrocatalytic reactions, the oxygen reduction reaction (ORR), was done following the most recent guidelines of theoretical studies on this topic. Aim of this work was to achieve a synergic effect of two different metals acting on different steps of the ORR. The catalytic activity of Ag, already known and characterized, was enhanced by the presence of a monolayer of cobalt subdivided into nanosized islands. To obtain such a controlled nanostructure, a novel method utilizing self-assembled monolayers (SAMs) as templates was employed. In a recent study, we were able to perform a confined electrodeposition of cobalt onto Ag(111) in a template formed by selectively desorbing a short-chain thiol (3-mercaptopropionic acid, MPA) from binary SAMs using 1-dodecanthiols (DDT). This method allows for an excellent control of the morphology of the deposit by varying the molar ratio of the two thiols. Because cobalt does not deposit on silver at an underpotential, the alternative approach of surface limited redox replacement (SLRR) was used. This method, recently developed by Adžić et al., consists of the use of a monolayer of a third metal, which can be deposited at an underpotential, as a template for the spontaneous deposition of a more noble metal. Herein, we choose zinc as template for the deposition of cobalt. Ag(111) crystals were covered by monolayer islands consisting of cobalt, with the surface atomic ratios ranging from 12 to 39% for cobalt. The catalytic activity of such samples towards ORR was evaluated and the best improvement in activity was found to be that of the sample with a cobalt percentage of approximately 30% with respect to the bare silver, which is in good agreement with theoretical hypotheses.
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Firenze via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Loglio
authors.forename: Elisa
authors.initials: E
authors.lastname: Lastraioli
authors.forename: Claudio
authors.initials: C
authors.lastname: Bianchini
authors.forename: Claudio
authors.initials: C
authors.lastname: Fontanesi
authors.forename: Massimo
authors.initials: M
authors.lastname: Innocenti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Lavacchi
authors.forename: Francesco
authors.initials: F
authors.lastname: Vizza
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Foresti
mesh_terms: D015097:3-Mercaptopropionic Acid / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D004595:Electroplating; D053768:Metal Nanoparticles / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D012834:Silver / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003035:Cobalt; D012834:Silver; D015097:3-Mercaptopropionic Acid